YQ(1)

NAME

yq is a portable command-line data file processor

SYNOPSIS

yq [eval/eval-all] [expression] files..

eval/e - (default) Apply the expression to each document in each yaml file in sequence

eval-all/ea - Loads all yaml documents of all yaml files and runs expression once

DESCRIPTION

a lightweight and portable command-line data file processor. yq uses jq (https://github.com/stedolan/jq) like syntax but works with yaml, json, xml, csv, properties and TOML files. It doesn’t yet support everything jq does - but it does support the most common operations and functions, and more is being added continuously.

This documentation is also available at https://mikefarah.gitbook.io/yq/ # QUICK GUIDE

  Read a value:

    yq '.a.b[0].c' file.yaml

  Pipe from STDIN:

    cat file.yaml | yq '.a.b[0].c'

  Update a yaml file, in place

    yq -i '.a.b[0].c = "cool"' file.yaml

  Update using environment variables

    NAME=mike yq -i '.a.b[0].c = strenv(NAME)' file.yaml

  Merge multiple files

    yq ea '. as $item ireduce ({}; . * $item )' path/to/*.yml

Note the use of ea to evaluate all files at once (instead of in sequence.)

  Multiple updates to a yaml file

    yq -i '
      .a.b[0].c = "cool" |
      .x.y.z = "foobar" |
      .person.name = strenv(NAME)
    ' file.yaml

See the documentation (https://mikefarah.gitbook.io/yq/) for more.

KNOWN ISSUES / MISSING FEATURES

•   yq attempts to preserve comment positions and whitespace as much as possible, but it does not handle all scenarios (see https://github.com/go-yaml/yaml/tree/v3 for details)

•   Powershell has its own...opinions: https://mikefarah.gitbook.io/yq/usage/tips-and-tricks#quotes-in-windows-powershell

BUGS / ISSUES / FEATURE REQUESTS

Please visit the GitHub page https://github.com/mikefarah/yq/.

HOW IT WORKS

In yq, expressions are made up of operators and pipes. A context of nodes is passed through the expression, and each operation takes the context as input and returns a new context as output. That output is piped in as input for the next operation in the expression.

Let’s break down the process step by step using a diagram. We’ll start with a single YAML document, apply an expression, and observe how the context changes at each step.

Given a document like:

    root:
      items:
        - name: apple
          type: fruit
        - name: carrot
          type: vegetable
        - name: banana
          type: fruit

You can use dot notation to access nested structures. For example, to access the name of the first item, you would use the expression .root.items[0].name, which would return apple.

But lets see how we could find all the fruit under items

  Step 1: Initial Context

The context starts at the root of the YAML document. In this case, the entire document is the initial context.

    root
    └── items
        ├── name: apple
        |   type: fruit
        ├── name: carrot
        |   type: vegetable
        └── name: banana
            type: fruit

  Step 2: Splatting the Array

Using the expression .root.items[], we “splat” the items array. This means each element of the array becomes its own node in the context:

    Node 1: { name: apple, type: fruit }
    Node 2: { name: carrot, type: vegetable }
    Node 3: { name: banana, type: fruit }

  Step 3: Filtering the Nodes

Next, we apply a filter to select only the nodes where type is fruit. The expression .root.items[] | select(.type == "fruit") filters the nodes:

    Filtered Node 1: { name: apple, type: fruit }
    Filtered Node 2: { name: banana, type: fruit }

  Step 4: Extracting a Field

Finally, we extract the name field from the filtered nodes using .root.items[] | select(.type == "fruit") | .name This results in:

    apple
    banana

  Simple assignment example

Given a document like:

    a: cat
    b: dog

with an expression:

    .a = .b

Like math expressions - operator precedence is important.

The = operator takes two arguments, a lhs expression, which in this case is .a and rhs expression which is .b.

It pipes the current, lets call it `root' context through the lhs expression of .a to return the node

    cat

Side note: this node holds not only its value `cat', but comments and metadata too, including path and parent information.

The = operator then pipes the `root' context through the rhs expression of .b to return the node

    dog

Both sides have now been evaluated, so now the operator copies across the value from the RHS (.b) to the LHS (.a), and it returns the now updated context:

    a: dog
    b: dog

  Complex assignment, operator precedence rules

Just like math expressions - yq expressions have an order of precedence. The pipe | operator has a low order of precedence, so operators with higher precedence will get evaluated first.

Most of the time, this is intuitively what you’d want, for instance .a = "cat" | .b = "dog" is effectively: (.a = "cat") | (.b = "dog").

However, this is not always the case, particularly if you have a complex LHS or RHS expression, for instance if you want to select particular nodes to update.

Lets say you had:

    - name: bob
      fruit: apple
    - name: sally
      fruit: orange

Lets say you wanted to update the sally entry to have fruit: `mango'. The incorrect way to do that is: .[] | select(.name == "sally") | .fruit = "mango".

Because | has a low operator precedence, this will be evaluated (incorrectly) as : (.[]) | (select(.name == "sally")) | (.fruit = "mango"). What you’ll see is only the updated segment returned:

    name: sally
    fruit: mango

Important: To properly update this YAML, you must wrap the entire LHS in parentheses. Think of it like using brackets in math to ensure the correct order of operations. (.[] | select(.name == "sally") | .fruit) = "mango"

Now that entire LHS expression is passed to the `assign' (=) operator, and the yaml is correctly updated and returned:

    - name: bob
      fruit: apple
    - name: sally
      fruit: mango

  Relative update (e.g. |=)

There is another form of the = operator which we call the relative form. It’s very similar to = but with one key difference when evaluating the RHS expression.

In the plain form, we pass in the `root' level context to the RHS expression. In relative form, we pass in each result of the LHS to the RHS expression. Let’s go through an example.

Given a document like:

    a: 1
    b: thing

with an expression:

    .a |= . + 1

Similar to the = operator, |= takes two operands, the LHS and RHS.

It pipes the current context (the whole document) through the LHS expression of .a to get the node value:

    1

Now it pipes that LHS context into the RHS expression . + 1 (whereas in the = plain form it piped the original document context into the RHS) to yield:

    2

The assignment operator then copies across the value from the RHS to the value on the LHS, and it returns the now updated `root' context:

    a: 2
    b: thing
    ```# Add
    Add behaves differently according to the type of the LHS:
    * arrays: concatenate
    * number scalars: arithmetic addition
    * string scalars: concatenate
    * maps: shallow merge (use the multiply operator (`*`) to deeply merge)
    Use `+=` as a relative append assign for things like increment. Note that `.a += .x` is equivalent to running `.a = .a + .x`.
    ## Concatenate arrays
    Given a sample.yml file of:
    ```yaml
    a:
      - 1
      - 2
    b:
      - 3
      - 4

then

    yq '.a + .b' sample.yml

will output

    - 1
    - 2
    - 3
    - 4

  Concatenate to existing array

Note that the styling of a is kept.

Given a sample.yml file of:

    a: [1,2]
    b:
      - 3
      - 4

then

    yq '.a += .b' sample.yml

will output

    a: [1, 2, 3, 4]
    b:
      - 3
      - 4

  Concatenate null to array

Given a sample.yml file of:

    a:
      - 1
      - 2

then

    yq '.a + null' sample.yml

will output

    - 1
    - 2

  Append to existing array

Note that the styling is copied from existing array elements

Given a sample.yml file of:

    a: ['dog']

then

    yq '.a += "cat"' sample.yml

will output

    a: ['dog', 'cat']

  Prepend to existing array

Given a sample.yml file of:

    a:
      - dog

then

    yq '.a = ["cat"] + .a' sample.yml

will output

    a:
      - cat
      - dog

  Add new object to array

Given a sample.yml file of:

    a:
      - dog: woof

then

    yq '.a + {"cat": "meow"}' sample.yml

will output

    - dog: woof
    - cat: meow

  Relative append

Given a sample.yml file of:

    a:
      a1:
        b:
          - cat
      a2:
        b:
          - dog
      a3: {}

then

    yq '.a[].b += ["mouse"]' sample.yml

will output

    a:
      a1:
        b:
          - cat
          - mouse
      a2:
        b:
          - dog
          - mouse
      a3:
        b:
          - mouse

  String concatenation

Given a sample.yml file of:

    a: cat
    b: meow

then

    yq '.a += .b' sample.yml

will output

    a: catmeow
    b: meow

  Number addition - float

If the lhs or rhs are floats then the expression will be calculated with floats.

Given a sample.yml file of:

    a: 3
    b: 4.9

then

    yq '.a = .a + .b' sample.yml

will output

    a: 7.9
    b: 4.9

  Number addition - int

If both the lhs and rhs are ints then the expression will be calculated with ints.

Given a sample.yml file of:

    a: 3
    b: 4

then

    yq '.a = .a + .b' sample.yml

will output

    a: 7
    b: 4

  Increment numbers

Given a sample.yml file of:

    a: 3
    b: 5

then

    yq '.[] += 1' sample.yml

will output

    a: 4
    b: 6

  Date addition

You can add durations to dates. Assumes RFC3339 date time format, see date-time operators (https://mikefarah.gitbook.io/yq/operators/date-time-operators) for more information.

Given a sample.yml file of:

    a: 2021-01-01T00:00:00Z

then

    yq '.a += "3h10m"' sample.yml

will output

    a: 2021-01-01T03:10:00Z

  Date addition - custom format

You can add durations to dates. See date-time operators (https://mikefarah.gitbook.io/yq/operators/date-time-operators) for more information.

Given a sample.yml file of:

    a: Saturday, 15-Dec-01 at 2:59AM GMT

then

    yq 'with_dtf("Monday, 02-Jan-06 at 3:04PM MST", .a += "3h1m")' sample.yml

will output

    a: Saturday, 15-Dec-01 at 6:00AM GMT

  Add to null

Adding to null simply returns the rhs

Running

    yq --null-input 'null + "cat"'

will output

    cat

  Add maps to shallow merge

Adding objects together shallow merges them. Use * to deeply merge.

Given a sample.yml file of:

    a:
      thing:
        name: Astuff
        value: x
      a1: cool
    b:
      thing:
        name: Bstuff
        legs: 3
      b1: neat

then

    yq '.a += .b' sample.yml

will output

    a:
      thing:
        name: Bstuff
        legs: 3
      a1: cool
      b1: neat
    b:
      thing:
        name: Bstuff
        legs: 3
      b1: neat

  Custom types: that are really strings

When custom tags are encountered, yq will try to decode the underlying type.

Given a sample.yml file of:

    a: !horse cat
    b: !goat _meow

then

    yq '.a += .b' sample.yml

will output

    a: !horse cat_meow
    b: !goat _meow

  Custom types: that are really numbers

When custom tags are encountered, yq will try to decode the underlying type.

Given a sample.yml file of:

    a: !horse 1.2
    b: !goat 2.3

then

    yq '.a += .b' sample.yml

will output

    a: !horse 3.5
    b: !goat 2.3

Alternative (Default value)

This operator is used to provide alternative (or default) values when a particular expression is either null or false.

  LHS is defined

Given a sample.yml file of:

    a: bridge

then

    yq '.a // "hello"' sample.yml

will output

    bridge

  LHS is not defined

Given a sample.yml file of:

    {}

then

    yq '.a // "hello"' sample.yml

will output

    hello

  LHS is null

Given a sample.yml file of:

    a: ~

then

    yq '.a // "hello"' sample.yml

will output

    hello

  LHS is false

Given a sample.yml file of:

    a: false

then

    yq '.a // "hello"' sample.yml

will output

    hello

  RHS is an expression

Given a sample.yml file of:

    a: false
    b: cat

then

    yq '.a // .b' sample.yml

will output

    cat

  Update or create - entity exists

This initialises a if it’s not present

Given a sample.yml file of:

    a: 1

then

    yq '(.a // (.a = 0)) += 1' sample.yml

will output

    a: 2

  Update or create - entity does not exist

This initialises a if it’s not present

Given a sample.yml file of:

    b: camel

then

    yq '(.a // (.a = 0)) += 1' sample.yml

will output

    b: camel
    a: 1

Anchor and Alias Operators

Use the alias and anchor operators to read and write yaml aliases and anchors. The explode operator normalises a yaml file (dereference (or expands) aliases and remove anchor names).

yq supports merge aliases (like <<: *blah) however this is no longer in the standard yaml spec (1.2) and so yq will automatically add the !!merge tag to these nodes as it is effectively a custom tag.

  NOTE –yaml-fix-merge-anchor-to-spec flag

yq doesn’t merge anchors <<: to spec, in some circumstances it incorrectly overrides existing keys when the spec documents not to do that.

To minimise disruption while still fixing the issue, a flag has been added to toggle this behaviour. This will first default to false; and log warnings to users. Then it will default to true (and still allow users to specify false if needed).

This flag also enables advanced merging, like inline maps, as well as fixes to ensure when exploding a particular path, neighbours are not affect ed.

Long story short, you should be setting this flag to true.

See examples of the flag differences below, where LEGACY is with the flag off; and FIXED is with the flag on.

  Merge one map

see https://yaml.org/type/merge.html

Given a sample.yml file of:

    - &CENTRE
      x: 1
      y: 2
    - &LEFT
      x: 0
      y: 2
    - &BIG
      r: 10
    - &SMALL
      r: 1
    - !!merge <<: *CENTRE
      r: 10

then

    yq '.[4] | explode(.)' sample.yml

will output

    x: 1
    y: 2
    r: 10

  Get anchor

Given a sample.yml file of:

    a: &billyBob cat

then

    yq '.a | anchor' sample.yml

will output

    billyBob

  Set anchor

Given a sample.yml file of:

    a: cat

then

    yq '.a anchor = "foobar"' sample.yml

will output

    a: &foobar cat

  Set anchor relatively using assign-update

Given a sample.yml file of:

    a:
      b: cat

then

    yq '.a anchor |= .b' sample.yml

will output

    a: &cat
      b: cat

  Get alias

Given a sample.yml file of:

    b: &billyBob meow
    a: *billyBob

then

    yq '.a | alias' sample.yml

will output

    billyBob

  Set alias

Given a sample.yml file of:

    b: &meow purr
    a: cat

then

    yq '.a alias = "meow"' sample.yml

will output

    b: &meow purr
    a: *meow

  Set alias to blank does nothing

Given a sample.yml file of:

    b: &meow purr
    a: cat

then

    yq '.a alias = ""' sample.yml

will output

    b: &meow purr
    a: cat

  Set alias relatively using assign-update

Given a sample.yml file of:

    b: &meow purr
    a:
      f: meow

then

    yq '.a alias |= .f' sample.yml

will output

    b: &meow purr
    a: *meow

  Explode alias and anchor

Given a sample.yml file of:

    f:
      a: &a cat
      b: *a

then

    yq 'explode(.f)' sample.yml

will output

    f:
      a: cat
      b: cat

  Explode with no aliases or anchors

Given a sample.yml file of:

    a: mike

then

    yq 'explode(.a)' sample.yml

will output

    a: mike

  Explode with alias keys

Given a sample.yml file of:

    f:
      a: &a cat
      *a : b

then

    yq 'explode(.f)' sample.yml

will output

    f:
      a: cat
      cat: b

  Dereference and update a field

Use explode with multiply to dereference an object

Given a sample.yml file of:

    item_value: &item_value
      value: true
    thingOne:
      name: item_1
      !!merge <<: *item_value
    thingTwo:
      name: item_2
      !!merge <<: *item_value

then

    yq '.thingOne |= (explode(.) | sort_keys(.)) * {"value": false}' sample.yml

will output

    item_value: &item_value
      value: true
    thingOne:
      name: item_1
      value: false
    thingTwo:
      name: item_2
      !!merge <<: *item_value

  LEGACY: Explode with merge anchors

Caution: this is for when –yaml-fix-merge-anchor-to-spec=false; it’s not to YAML spec because the merge anchors incorrectly override the object values (foobarList.b is set to bar_b when it should still be foobarList_b). Flag will default to true in late 2025

Given a sample.yml file of:

    foo: &foo
      a: foo_a
      thing: foo_thing
      c: foo_c
    bar: &bar
      b: bar_b
      thing: bar_thing
      c: bar_c
    foobarList:
      b: foobarList_b
      !!merge <<:
        - *foo
        - *bar
      c: foobarList_c
    foobar:
      c: foobar_c
      !!merge <<: *foo
      thing: foobar_thing

then

    yq 'explode(.)' sample.yml

will output

    foo:
      a: foo_a
      thing: foo_thing
      c: foo_c
    bar:
      b: bar_b
      thing: bar_thing
      c: bar_c
    foobarList:
      b: bar_b
      thing: foo_thing
      c: foobarList_c
      a: foo_a
    foobar:
      c: foo_c
      a: foo_a
      thing: foobar_thing

  LEGACY: Merge multiple maps

see https://yaml.org/type/merge.html. This has the correct data, but the wrong key order; set –yaml-fix-merge-anchor-to-spec=true to fix the key order.

Given a sample.yml file of:

    - &CENTRE
      x: 1
      y: 2
    - &LEFT
      x: 0
      y: 2
    - &BIG
      r: 10
    - &SMALL
      r: 1
    - !!merge <<:
        - *CENTRE
        - *BIG

then

    yq '.[4] | explode(.)' sample.yml

will output

    r: 10
    x: 1
    y: 2

  LEGACY: Override

see https://yaml.org/type/merge.html. This has the correct data, but the wrong key order; set –yaml-fix-merge-anchor-to-spec=true to fix the key order.

Given a sample.yml file of:

    - &CENTRE
      x: 1
      y: 2
    - &LEFT
      x: 0
      y: 2
    - &BIG
      r: 10
    - &SMALL
      r: 1
    - !!merge <<:
        - *BIG
        - *LEFT
        - *SMALL
      x: 1

then

    yq '.[4] | explode(.)' sample.yml

will output

    r: 10
    x: 1
    y: 2

  FIXED: Explode with merge anchors

Set --yaml-fix-merge-anchor-to-spec=true to get this correct merge behaviour (flag will default to true in late 2025). Observe that foobarList.b property is still foobarList_b.

Given a sample.yml file of:

    foo: &foo
      a: foo_a
      thing: foo_thing
      c: foo_c
    bar: &bar
      b: bar_b
      thing: bar_thing
      c: bar_c
    foobarList:
      b: foobarList_b
      !!merge <<:
        - *foo
        - *bar
      c: foobarList_c
    foobar:
      c: foobar_c
      !!merge <<: *foo
      thing: foobar_thing

then

    yq 'explode(.)' sample.yml

will output

    foo:
      a: foo_a
      thing: foo_thing
      c: foo_c
    bar:
      b: bar_b
      thing: bar_thing
      c: bar_c
    foobarList:
      b: foobarList_b
      a: foo_a
      thing: foo_thing
      c: foobarList_c
    foobar:
      c: foobar_c
      a: foo_a
      thing: foobar_thing

  FIXED: Merge multiple maps

Set --yaml-fix-merge-anchor-to-spec=true to get this correct merge behaviour (flag will default to true in late 2025). Taken from https://yaml.org/type/merge.html. Same values as legacy, but with the correct key order.

Given a sample.yml file of:

    - &CENTRE
      x: 1
      y: 2
    - &LEFT
      x: 0
      y: 2
    - &BIG
      r: 10
    - &SMALL
      r: 1
    - !!merge <<:
        - *CENTRE
        - *BIG

then

    yq '.[4] | explode(.)' sample.yml

will output

    x: 1
    y: 2
    r: 10

  FIXED: Override

Set --yaml-fix-merge-anchor-to-spec=true to get this correct merge behaviour (flag will default to true in late 2025). Taken from https://yaml.org/type/merge.html. Same values as legacy, but with the correct key order.

Given a sample.yml file of:

    - &CENTRE
      x: 1
      y: 2
    - &LEFT
      x: 0
      y: 2
    - &BIG
      r: 10
    - &SMALL
      r: 1
    - !!merge <<:
        - *BIG
        - *LEFT
        - *SMALL
      x: 1

then

    yq '.[4] | explode(.)' sample.yml

will output

    r: 10
    y: 2
    x: 1

  Exploding inline merge anchor

Set --yaml-fix-merge-anchor-to-spec=true to get this correct merge behaviour (flag will default to true in late 2025).

Given a sample.yml file of:

    a:
      b: &b 42
    !!merge <<:
      c: *b

then

    yq 'explode(.) | sort_keys(.)' sample.yml

will output

    a:
      b: 42
    c: 42

Array to Map

Use this operator to convert an array to..a map. The indices are used as map keys, null values in the array are skipped over.

Behind the scenes, this is implemented using reduce:

    (.[] | select(. != null) ) as $i ireduce({}; .[$i | key] = $i)

  Simple example

Given a sample.yml file of:

    cool:
      - null
      - null
      - hello

then

    yq '.cool |= array_to_map' sample.yml

will output

    cool:
      2: hello

Assign (Update)

This operator is used to update node values. It can be used in either the:

  plain form: =

Which will set the LHS node values equal to the RHS node values. The RHS expression is run against the matching nodes in the pipeline.

  relative form: |=

This will do a similar thing to the plain form, but the RHS expression is run with each LHS node as context. This is useful for updating values based on old values, e.g. increment.

  Flags

•   c clobber custom tags

  Create yaml file

Running

    yq --null-input '.a.b = "cat" | .x = "frog"'

will output

    a:
      b: cat
    x: frog

  Update node to be the child value

Given a sample.yml file of:

    a:
      b:
        g: foof

then

    yq '.a |= .b' sample.yml

will output

    a:
      g: foof

  Double elements in an array

Given a sample.yml file of:

    - 1
    - 2
    - 3

then

    yq '.[] |= . * 2' sample.yml

will output

    - 2
    - 4
    - 6

  Update node from another file

Note this will also work when the second file is a scalar (string/number)

Given a sample.yml file of:

    a: apples

And another sample another.yml file of:

    b: bob

then

    yq eval-all 'select(fileIndex==0).a = select(fileIndex==1) | select(fileIndex==0)' sample.yml another.yml

will output

    a:
      b: bob

  Update node to be the sibling value

Given a sample.yml file of:

    a:
      b: child
    b: sibling

then

    yq '.a = .b' sample.yml

will output

    a: sibling
    b: sibling

  Updated multiple paths

Given a sample.yml file of:

    a: fieldA
    b: fieldB
    c: fieldC

then

    yq '(.a, .c) = "potato"' sample.yml

will output

    a: potato
    b: fieldB
    c: potato

  Update string value

Given a sample.yml file of:

    a:
      b: apple

then

    yq '.a.b = "frog"' sample.yml

will output

    a:
      b: frog

  Update string value via |=

Note there is no difference between = and |= when the RHS is a scalar

Given a sample.yml file of:

    a:
      b: apple

then

    yq '.a.b |= "frog"' sample.yml

will output

    a:
      b: frog

  Update deeply selected results

Note that the LHS is wrapped in brackets! This is to ensure we don’t first filter out the yaml and then update the snippet.

Given a sample.yml file of:

    a:
      b: apple
      c: cactus

then

    yq '(.a[] | select(. == "apple")) = "frog"' sample.yml

will output

    a:
      b: frog
      c: cactus

  Update array values

Given a sample.yml file of:

    - candy
    - apple
    - sandy

then

    yq '(.[] | select(. == "*andy")) = "bogs"' sample.yml

will output

    - bogs
    - apple
    - bogs

  Update empty object

Given a sample.yml file of:

    {}

then

    yq '.a.b |= "bogs"' sample.yml

will output

    a:
      b: bogs

  Update node value that has an anchor

Anchor will remain

Given a sample.yml file of:

    a: &cool cat

then

    yq '.a = "dog"' sample.yml

will output

    a: &cool dog

  Update empty object and array

Given a sample.yml file of:

    {}

then

    yq '.a.b.[0] |= "bogs"' sample.yml

will output

    a:
      b:
        - bogs

  Custom types are maintained by default

Given a sample.yml file of:

    a: !cat meow
    b: !dog woof

then

    yq '.a = .b' sample.yml

will output

    a: !cat woof
    b: !dog woof

  Custom types: clobber

Use the c option to clobber custom tags

Given a sample.yml file of:

    a: !cat meow
    b: !dog woof

then

    yq '.a =c .b' sample.yml

will output

    a: !dog woof
    b: !dog woof

Boolean Operators

The or and and operators take two parameters and return a boolean result.

not flips a boolean from true to false, or vice versa.

any will return true if there are any true values in an array sequence, and all will return true if all elements in an array are true.

any_c(condition) and all_c(condition) are like any and all but they take a condition expression that is used against each element to determine if it’s true. Note: in jq you can simply pass a condition to any or all and it simply works - yq isn’t that clever..yet

These are most commonly used with the select operator to filter particular nodes.

  Related Operators

•   equals / not equals (==, !=) operators here (https://mikefarah.gitbook.io/yq/operators/equals)

•   comparison (>=, < etc) operators here (https://mikefarah.gitbook.io/yq/operators/compare)

•   select operator here (https://mikefarah.gitbook.io/yq/operators/select)

  or example

Running

    yq --null-input 'true or false'

will output

    true

  “yes” and “no” are strings

In the yaml 1.2 standard, support for yes/no as booleans was dropped - they are now considered strings. See `10.2.1.2. Boolean' in https://yaml.org/spec/1.2.2/

Given a sample.yml file of:

    - yes
    - no

then

    yq '.[] | tag' sample.yml

will output

    !!str
    !!str

  and example

Running

    yq --null-input 'true and false'

will output

    false

  Matching nodes with select, equals and or

Given a sample.yml file of:

    - a: bird
      b: dog
    - a: frog
      b: bird
    - a: cat
      b: fly

then

    yq '[.[] | select(.a == "cat" or .b == "dog")]' sample.yml

will output

    - a: bird
      b: dog
    - a: cat
      b: fly

  any returns true if any boolean in a given array is true

Given a sample.yml file of:

    - false
    - true

then

    yq 'any' sample.yml

will output

    true

  any returns false for an empty array

Given a sample.yml file of:

    []

then

    yq 'any' sample.yml

will output

    false

  any_c returns true if any element in the array is true for the given condition.

Given a sample.yml file of:

    a:
      - rad
      - awesome
    b:
      - meh
      - whatever

then

    yq '.[] |= any_c(. == "awesome")' sample.yml

will output

    a: true
    b: false

  all returns true if all booleans in a given array are true

Given a sample.yml file of:

    - true
    - true

then

    yq 'all' sample.yml

will output

    true

  all returns true for an empty array

Given a sample.yml file of:

    []

then

    yq 'all' sample.yml

will output

    true

  all_c returns true if all elements in the array are true for the given condition.

Given a sample.yml file of:

    a:
      - rad
      - awesome
    b:
      - meh
      - 12

then

    yq '.[] |= all_c(tag == "!!str")' sample.yml

will output

    a: true
    b: false

  Not true is false

Running

    yq --null-input 'true | not'

will output

    false

  Not false is true

Running

    yq --null-input 'false | not'

will output

    true

  String values considered to be true

Running

    yq --null-input '"cat" | not'

will output

    false

  Empty string value considered to be true

Running

    yq --null-input '"" | not'

will output

    false

  Numbers are considered to be true

Running

    yq --null-input '1 | not'

will output

    false

  Zero is considered to be true

Running

    yq --null-input '0 | not'

will output

    false

  Null is considered to be false

Running

    yq --null-input '~ | not'

will output

    true

Collect into Array

This creates an array using the expression between the square brackets.

  Collect empty

Running

    yq --null-input '[]'

will output

    []

  Collect single

Running

    yq --null-input '["cat"]'

will output

    - cat

  Collect many

Given a sample.yml file of:

    a: cat
    b: dog

then

    yq '[.a, .b]' sample.yml

will output

    - cat
    - dog

Column

Returns the column of the matching node. Starts from 1, 0 indicates there was no column data.

Column is the number of characters that precede that node on the line it starts.

  Returns column of value node

Given a sample.yml file of:

    a: cat
    b: bob

then

    yq '.b | column' sample.yml

will output

    4

  Returns column of key node

Pipe through the key operator to get the column of the key

Given a sample.yml file of:

    a: cat
    b: bob

then

    yq '.b | key | column' sample.yml

will output

    1

  First column is 1

Given a sample.yml file of:

    a: cat

then

    yq '.a | key | column' sample.yml

will output

    1

  No column data is 0

Running

    yq --null-input '{"a": "new entry"} | column'

will output

    0

Comment Operators

Use these comment operators to set or retrieve comments. Note that line comments on maps/arrays are actually set on the key node as opposed to the value (map/array). See below for examples.

Like the = and |= assign operators, the same syntax applies when updating comments:

  plain form: =

This will set the LHS nodes’ comments equal to the expression on the RHS. The RHS is run against the matching nodes in the pipeline

  relative form: |=

This is similar to the plain form, but it evaluates the RHS with each matching LHS node as context. This is useful if you want to set the comments as a relative expression of the node, for instance its value or path.

  Set line comment

Set the comment on the key node for more reliability (see below).

Given a sample.yml file of:

    a: cat

then

    yq '.a line_comment="single"' sample.yml

will output

    a: cat # single

  Set line comment of a maps/arrays

For maps and arrays, you need to set the line comment on the key node. This will also work for scalars.

Given a sample.yml file of:

    a:
      b: things

then

    yq '(.a | key) line_comment="single"' sample.yml

will output

    a: # single
      b: things

  Use update assign to perform relative updates

Given a sample.yml file of:

    a: cat
    b: dog

then

    yq '.. line_comment |= .' sample.yml

will output

    a: cat # cat
    b: dog # dog

  Where is the comment - map key example

The underlying yaml parser can assign comments in a document to surprising nodes. Use an expression like this to find where you comment is. `p' indicates the path, `isKey' is if the node is a map key (as opposed to a map value). From this, you can see the `hello-world-comment' is actually on the `hello' key

Given a sample.yml file of:

    hello: # hello-world-comment
      message: world

then

    yq '[... | {"p": path | join("."), "isKey": is_key, "hc": headComment, "lc": lineComment, "fc": footComment}]' sample.yml

will output

    - p: ""
      isKey: false
      hc: ""
      lc: ""
      fc: ""
    - p: hello
      isKey: true
      hc: ""
      lc: hello-world-comment
      fc: ""
    - p: hello
      isKey: false
      hc: ""
      lc: ""
      fc: ""
    - p: hello.message
      isKey: true
      hc: ""
      lc: ""
      fc: ""
    - p: hello.message
      isKey: false
      hc: ""
      lc: ""
      fc: ""

  Retrieve comment - map key example

From the previous example, we know that the comment is on the `hello' key as a lineComment

Given a sample.yml file of:

    hello: # hello-world-comment
      message: world

then

    yq '.hello | key | line_comment' sample.yml

will output

    hello-world-comment

  Where is the comment - array example

The underlying yaml parser can assign comments in a document to surprising nodes. Use an expression like this to find where you comment is. `p' indicates the path, `isKey' is if the node is a map key (as opposed to a map value). From this, you can see the `under-name-comment' is actually on the first child

Given a sample.yml file of:

    name:
      # under-name-comment
      - first-array-child

then

    yq '[... | {"p": path | join("."), "isKey": is_key, "hc": headComment, "lc": lineComment, "fc": footComment}]' sample.yml

will output

    - p: ""
      isKey: false
      hc: ""
      lc: ""
      fc: ""
    - p: name
      isKey: true
      hc: ""
      lc: ""
      fc: ""
    - p: name
      isKey: false
      hc: ""
      lc: ""
      fc: ""
    - p: name.0
      isKey: false
      hc: under-name-comment
      lc: ""
      fc: ""

  Retrieve comment - array example

From the previous example, we know that the comment is on the first child as a headComment

Given a sample.yml file of:

    name:
      # under-name-comment
      - first-array-child

then

    yq '.name[0] | headComment' sample.yml

will output

    under-name-comment

  Set head comment

Given a sample.yml file of:

    a: cat

then

    yq '. head_comment="single"' sample.yml

will output

    # single
    a: cat

  Set head comment of a map entry

Given a sample.yml file of:

    f: foo
    a:
      b: cat

then

    yq '(.a | key) head_comment="single"' sample.yml

will output

    f: foo
    # single
    a:
      b: cat

  Set foot comment, using an expression

Given a sample.yml file of:

    a: cat

then

    yq '. foot_comment=.a' sample.yml

will output

    a: cat
    # cat

  Remove comment

Given a sample.yml file of:

    a: cat # comment
    b: dog # leave this

then

    yq '.a line_comment=""' sample.yml

will output

    a: cat
    b: dog # leave this

  Remove (strip) all comments

Note the use of ... to ensure key nodes are included.

Given a sample.yml file of:

    # hi
    a: cat # comment
    # great
    b: # key comment

then

    yq '... comments=""' sample.yml

will output

    a: cat
    b:

  Get line comment

Given a sample.yml file of:

    # welcome!
    a: cat # meow
    # have a great day

then

    yq '.a | line_comment' sample.yml

will output

    meow

  Get head comment

Given a sample.yml file of:

    # welcome!
    a: cat # meow
    # have a great day

then

    yq '. | head_comment' sample.yml

will output

    welcome!

  Head comment with document split

Given a sample.yml file of:

    # welcome!
    ---
    # bob
    a: cat # meow
    # have a great day

then

    yq 'head_comment' sample.yml

will output

    welcome!
    bob

  Get foot comment

Given a sample.yml file of:

    # welcome!
    a: cat # meow
    # have a great day
    # no really

then

    yq '. | foot_comment' sample.yml

will output

    have a great day
    no really

Compare Operators

Comparison operators (>, >=, <, <=) can be used for comparing scalar values of the same time.

The following types are currently supported:

•   numbers

•   strings

•   datetimes

  Related Operators

•   equals / not equals (==, !=) operators here (https://mikefarah.gitbook.io/yq/operators/equals)

•   boolean operators (and, or, any etc) here (https://mikefarah.gitbook.io/yq/operators/boolean-operators)

•   select operator here (https://mikefarah.gitbook.io/yq/operators/select)

  Compare numbers (>)

Given a sample.yml file of:

    a: 5
    b: 4

then

    yq '.a > .b' sample.yml

will output

    true

  Compare equal numbers (>=)

Given a sample.yml file of:

    a: 5
    b: 5

then

    yq '.a >= .b' sample.yml

will output

    true

  Compare strings

Compares strings by their bytecode.

Given a sample.yml file of:

    a: zoo
    b: apple

then

    yq '.a > .b' sample.yml

will output

    true

  Compare date times

You can compare date times. Assumes RFC3339 date time format, see date-time operators (https://mikefarah.gitbook.io/yq/operators/date-time-operators) for more information.

Given a sample.yml file of:

    a: 2021-01-01T03:10:00Z
    b: 2020-01-01T03:10:00Z

then

    yq '.a > .b' sample.yml

will output

    true

  Both sides are null: > is false

Running

    yq --null-input '.a > .b'

will output

    false

  Both sides are null: >= is true

Running

    yq --null-input '.a >= .b'

will output

    true

Contains

This returns true if the context contains the passed in parameter, and false otherwise. For arrays, this will return true if the passed in array is contained within the array. For strings, it will return true if the string is a substring.

{% hint style=“warning” %}

Note that, just like jq, when checking if an array of strings contains another, this will use contains and not equals to check each string. This means an expression like contains(["cat"]) will return true for an array ["cats"].

See the “Array has a subset array” example below on how to check for a subset.

{% endhint %}

  Array contains array

Array is equal or subset of

Given a sample.yml file of:

    - foobar
    - foobaz
    - blarp

then

    yq 'contains(["baz", "bar"])' sample.yml

will output

    true

  Array has a subset array

Subtract the superset array from the subset, if there’s anything left, it’s not a subset

Given a sample.yml file of:

    - foobar
    - foobaz
    - blarp

then

    yq '["baz", "bar"] - . | length == 0' sample.yml

will output

    false

  Object included in array

Given a sample.yml file of:

    "foo": 12
    "bar":
      - 1
      - 2
      - "barp": 12
        "blip": 13

then

    yq 'contains({"bar": [{"barp": 12}]})' sample.yml

will output

    true

  Object not included in array

Given a sample.yml file of:

    "foo": 12
    "bar":
      - 1
      - 2
      - "barp": 12
        "blip": 13

then

    yq 'contains({"foo": 12, "bar": [{"barp": 15}]})' sample.yml

will output

    false

  String contains substring

Given a sample.yml file of:

    foobar

then

    yq 'contains("bar")' sample.yml

will output

    true

  String equals string

Given a sample.yml file of:

    meow

then

    yq 'contains("meow")' sample.yml

will output

    true

Create, Collect into Object

This is used to construct objects (or maps). This can be used against existing yaml, or to create fresh yaml documents.

  Collect empty object

Running

    yq --null-input '{}'

will output

    {}

  Wrap (prefix) existing object

Given a sample.yml file of:

    name: Mike

then

    yq '{"wrap": .}' sample.yml

will output

    wrap:
      name: Mike

  Using splat to create multiple objects

Given a sample.yml file of:

    name: Mike
    pets:
      - cat
      - dog

then

    yq '{.name: .pets.[]}' sample.yml

will output

    Mike: cat
    Mike: dog

  Working with multiple documents

Given a sample.yml file of:

    name: Mike
    pets:
      - cat
      - dog
    ---
    name: Rosey
    pets:
      - monkey
      - sheep

then

    yq '{.name: .pets.[]}' sample.yml

will output

    Mike: cat
    Mike: dog
    ---
    Rosey: monkey
    Rosey: sheep

  Creating yaml from scratch

Running

    yq --null-input '{"wrap": "frog"}'

will output

    wrap: frog

  Creating yaml from scratch with multiple objects

Running

    yq --null-input '(.a.b = "foo") | (.d.e = "bar")'

will output

    a:
      b: foo
    d:
      e: bar

Date Time

Various operators for parsing and manipulating dates.

  Date time formatting

This uses Golang’s built in time library for parsing and formatting date times.

When not specified, the RFC3339 standard is assumed 2006-01-02T15:04:05Z07:00 for parsing.

To specify a custom parsing format, use the with_dtf operator. The first parameter sets the datetime parsing format for the expression in the second parameter. The expression can be any valid yq expression tree.

    yq 'with_dtf("myformat"; .a + "3h" | tz("Australia/Melbourne"))'

See the library docs (https://pkg.go.dev/time#pkg-constants) for examples of formatting options.

  Timezones

This uses Golang’s built in LoadLocation function to parse timezones strings. See the library docs (https://pkg.go.dev/time#LoadLocation) for more details.

  Durations

Durations are parsed using Golang’s built in ParseDuration (https://pkg.go.dev/time#ParseDuration) function.

You can add durations to time using the + operator.

  Format: from standard RFC3339 format

Providing a single parameter assumes a standard RFC3339 datetime format. If the target format is not a valid yaml datetime format, the result will be a string tagged node.

Given a sample.yml file of:

    a: 2001-12-15T02:59:43.1Z

then

    yq '.a |= format_datetime("Monday, 02-Jan-06 at 3:04PM")' sample.yml

will output

    a: Saturday, 15-Dec-01 at 2:59AM

  Format: from custom date time

Use with_dtf to set a custom datetime format for parsing.

Given a sample.yml file of:

    a: Saturday, 15-Dec-01 at 2:59AM

then

    yq '.a |= with_dtf("Monday, 02-Jan-06 at 3:04PM"; format_datetime("2006-01-02"))' sample.yml

will output

    a: 2001-12-15

  Format: get the day of the week

Given a sample.yml file of:

    a: 2001-12-15

then

    yq '.a | format_datetime("Monday")' sample.yml

will output

    Saturday

  Now

Given a sample.yml file of:

    a: cool

then

    yq '.updated = now' sample.yml

will output

    a: cool
    updated: 2021-05-19T01:02:03Z

  From Unix

Converts from unix time. Note, you don’t have to pipe through the tz operator :)

Running

    yq --null-input '1675301929 | from_unix | tz("UTC")'

will output

    2023-02-02T01:38:49Z

  To Unix

Converts to unix time

Running

    yq --null-input 'now | to_unix'

will output

    1621386123

  Timezone: from standard RFC3339 format

Returns a new datetime in the specified timezone. Specify standard IANA Time Zone format or `utc', `local'. When given a single parameter, this assumes the datetime is in RFC3339 format.

Given a sample.yml file of:

    a: cool

then

    yq '.updated = (now | tz("Australia/Sydney"))' sample.yml

will output

    a: cool
    updated: 2021-05-19T11:02:03+10:00

  Timezone: with custom format

Specify standard IANA Time Zone format or `utc', `local'

Given a sample.yml file of:

    a: Saturday, 15-Dec-01 at 2:59AM GMT

then

    yq '.a |= with_dtf("Monday, 02-Jan-06 at 3:04PM MST"; tz("Australia/Sydney"))' sample.yml

will output

    a: Saturday, 15-Dec-01 at 1:59PM AEDT

  Add and tz custom format

Specify standard IANA Time Zone format or `utc', `local'

Given a sample.yml file of:

    a: Saturday, 15-Dec-01 at 2:59AM GMT

then

    yq '.a |= with_dtf("Monday, 02-Jan-06 at 3:04PM MST"; tz("Australia/Sydney"))' sample.yml

will output

    a: Saturday, 15-Dec-01 at 1:59PM AEDT

  Date addition

Given a sample.yml file of:

    a: 2021-01-01T00:00:00Z

then

    yq '.a += "3h10m"' sample.yml

will output

    a: 2021-01-01T03:10:00Z

  Date subtraction

You can subtract durations from dates. Assumes RFC3339 date time format, see date-time operators (https://mikefarah.gitbook.io/yq/operators/datetime#date-time-formattings) for more information.

Given a sample.yml file of:

    a: 2021-01-01T03:10:00Z

then

    yq '.a -= "3h10m"' sample.yml

will output

    a: 2021-01-01T00:00:00Z

  Date addition - custom format

Given a sample.yml file of:

    a: Saturday, 15-Dec-01 at 2:59AM GMT

then

    yq 'with_dtf("Monday, 02-Jan-06 at 3:04PM MST"; .a += "3h1m")' sample.yml

will output

    a: Saturday, 15-Dec-01 at 6:00AM GMT

  Date script with custom format

You can embed full expressions in with_dtf if needed.

Given a sample.yml file of:

    a: Saturday, 15-Dec-01 at 2:59AM GMT

then

    yq 'with_dtf("Monday, 02-Jan-06 at 3:04PM MST"; .a = (.a + "3h1m" | tz("Australia/Perth")))' sample.yml

will output

    a: Saturday, 15-Dec-01 at 2:00PM AWST

Delete

Deletes matching entries in maps or arrays.

  Delete entry in map

Given a sample.yml file of:

    a: cat
    b: dog

then

    yq 'del(.b)' sample.yml

will output

    a: cat

  Delete nested entry in map

Given a sample.yml file of:

    a:
      a1: fred
      a2: frood

then

    yq 'del(.a.a1)' sample.yml

will output

    a:
      a2: frood

  Delete entry in array

Given a sample.yml file of:

    - 1
    - 2
    - 3

then

    yq 'del(.[1])' sample.yml

will output

    - 1
    - 3

  Delete nested entry in array

Given a sample.yml file of:

    - a: cat
      b: dog

then

    yq 'del(.[0].a)' sample.yml

will output

    - b: dog

  Delete no matches

Given a sample.yml file of:

    a: cat
    b: dog

then

    yq 'del(.c)' sample.yml

will output

    a: cat
    b: dog

  Delete matching entries

Given a sample.yml file of:

    a: cat
    b: dog
    c: bat

then

    yq 'del( .[] | select(. == "*at") )' sample.yml

will output

    b: dog

  Recursively delete matching keys

Given a sample.yml file of:

    a:
      name: frog
      b:
        name: blog
        age: 12

then

    yq 'del(.. | select(has("name")).name)' sample.yml

will output

    a:
      b:
        age: 12

Divide

Divide behaves differently according to the type of the LHS: * strings: split by the divider * number: arithmetic division

  String split

Given a sample.yml file of:

    a: cat_meow
    b: _

then

    yq '.c = .a / .b' sample.yml

will output

    a: cat_meow
    b: _
    c:
      - cat
      - meow

  Number division

The result during division is calculated as a float

Given a sample.yml file of:

    a: 12
    b: 2.5

then

    yq '.a = .a / .b' sample.yml

will output

    a: 4.8
    b: 2.5

  Number division by zero

Dividing by zero results in +Inf or -Inf

Given a sample.yml file of:

    a: 1
    b: -1

then

    yq '.a = .a / 0 | .b = .b / 0' sample.yml

will output

    a: !!float +Inf
    b: !!float -Inf

Document Index

Use the documentIndex operator (or the di shorthand) to select nodes of a particular document.

  Retrieve a document index

Given a sample.yml file of:

    a: cat
    ---
    a: frog

then

    yq '.a | document_index' sample.yml

will output

    0
    ---
    1

  Retrieve a document index, shorthand

Given a sample.yml file of:

    a: cat
    ---
    a: frog

then

    yq '.a | di' sample.yml

will output

    0
    ---
    1

  Filter by document index

Given a sample.yml file of:

    a: cat
    ---
    a: frog

then

    yq 'select(document_index == 1)' sample.yml

will output

    a: frog

  Filter by document index shorthand

Given a sample.yml file of:

    a: cat
    ---
    a: frog

then

    yq 'select(di == 1)' sample.yml

will output

    a: frog

  Print Document Index with matches

Given a sample.yml file of:

    a: cat
    ---
    a: frog

then

    yq '.a | ({"match": ., "doc": document_index})' sample.yml

will output

    match: cat
    doc: 0
    ---
    match: frog
    doc: 1

Encoder / Decoder

Encode operators will take the piped in object structure and encode it as a string in the desired format. The decode operators do the opposite, they take a formatted string and decode it into the relevant object structure.

Note that you can optionally pass an indent value to the encode functions (see below).

These operators are useful to process yaml documents that have stringified embedded yaml/json/props in them.

Format | Decode (from string) | Encode (to string)
Yaml | from_yaml/@yamld | to_yaml(i)/@yaml
JSON | from_json/@jsond | to_json(i)/@json
Properties | from_props/@propsd | to_props/@props
CSV | from_csv/@csvd | to_csv/@csv
TSV | from_tsv/@tsvd | to_tsv/@tsv
XML | from_xml/@xmld | to_xml(i)/@xml
Base64 | @base64d | @base64
URI | @urid | @uri
Shell |  | @sh

See CSV and TSV documentation (https://mikefarah.gitbook.io/yq/usage/csv-tsv) for accepted formats.

XML uses the --xml-attribute-prefix and xml-content-name flags to identify attributes and content fields.

Base64 assumes rfc4648 (https://rfc-editor.org/rfc/rfc4648.html) encoding. Encoding and decoding both assume that the content is a utf-8 string and not binary content.

  Encode value as json string

Given a sample.yml file of:

    a:
      cool: thing

then

    yq '.b = (.a | to_json)' sample.yml

will output

    a:
      cool: thing
    b: |
      {
        "cool": "thing"
      }

  Encode value as json string, on one line

Pass in a 0 indent to print json on a single line.

Given a sample.yml file of:

    a:
      cool: thing

then

    yq '.b = (.a | to_json(0))' sample.yml

will output

    a:
      cool: thing
    b: '{"cool":"thing"}'

  Encode value as json string, on one line shorthand

Pass in a 0 indent to print json on a single line.

Given a sample.yml file of:

    a:
      cool: thing

then

    yq '.b = (.a | @json)' sample.yml

will output

    a:
      cool: thing
    b: '{"cool":"thing"}'

  Decode a json encoded string

Keep in mind JSON is a subset of YAML. If you want idiomatic yaml, pipe through the style operator to clear out the JSON styling.

Given a sample.yml file of:

    a: '{"cool":"thing"}'

then

    yq '.a | from_json | ... style=""' sample.yml

will output

    cool: thing

  Encode value as props string

Given a sample.yml file of:

    a:
      cool: thing

then

    yq '.b = (.a | @props)' sample.yml

will output

    a:
      cool: thing
    b: |
      cool = thing

  Decode props encoded string

Given a sample.yml file of:

    a: |-
      cats=great
      dogs=cool as well

then

    yq '.a |= @propsd' sample.yml

will output

    a:
      cats: great
      dogs: cool as well

  Decode csv encoded string

Given a sample.yml file of:

    a: |-
      cats,dogs
      great,cool as well

then

    yq '.a |= @csvd' sample.yml

will output

    a:
      - cats: great
        dogs: cool as well

  Decode tsv encoded string

Given a sample.yml file of:

    a: |-
      cats  dogs
      great cool as well

then

    yq '.a |= @tsvd' sample.yml

will output

    a:
      - cats: great
        dogs: cool as well

  Encode value as yaml string

Indent defaults to 2

Given a sample.yml file of:

    a:
      cool:
        bob: dylan

then

    yq '.b = (.a | to_yaml)' sample.yml

will output

    a:
      cool:
        bob: dylan
    b: |
      cool:
        bob: dylan

  Encode value as yaml string, with custom indentation

You can specify the indentation level as the first parameter.

Given a sample.yml file of:

    a:
      cool:
        bob: dylan

then

    yq '.b = (.a | to_yaml(8))' sample.yml

will output

    a:
      cool:
        bob: dylan
    b: |
      cool:
              bob: dylan

  Decode a yaml encoded string

Given a sample.yml file of:

    a: 'foo: bar'

then

    yq '.b = (.a | from_yaml)' sample.yml

will output

    a: 'foo: bar'
    b:
      foo: bar

  Update a multiline encoded yaml string

Given a sample.yml file of:

    a: |
      foo: bar
      baz: dog

then

    yq '.a |= (from_yaml | .foo = "cat" | to_yaml)' sample.yml

will output

    a: |
      foo: cat
      baz: dog

  Update a single line encoded yaml string

Given a sample.yml file of:

    a: 'foo: bar'

then

    yq '.a |= (from_yaml | .foo = "cat" | to_yaml)' sample.yml

will output

    a: 'foo: cat'

  Encode array of scalars as csv string

Scalars are strings, numbers and booleans.

Given a sample.yml file of:

    - cat
    - thing1,thing2
    - true
    - 3.40

then

    yq '@csv' sample.yml

will output

    cat,"thing1,thing2",true,3.40

  Encode array of arrays as csv string

Given a sample.yml file of:

    - - cat
      - thing1,thing2
      - true
      - 3.40
    - - dog
      - thing3
      - false
      - 12

then

    yq '@csv' sample.yml

will output

    cat,"thing1,thing2",true,3.40
    dog,thing3,false,12

  Encode array of arrays as tsv string

Scalars are strings, numbers and booleans.

Given a sample.yml file of:

    - - cat
      - thing1,thing2
      - true
      - 3.40
    - - dog
      - thing3
      - false
      - 12

then

    yq '@tsv' sample.yml

will output

    cat thing1,thing2   true    3.40
    dog thing3  false   12

  Encode value as xml string

Given a sample.yml file of:

    a:
      cool:
        foo: bar
        +@id: hi

then

    yq '.a | to_xml' sample.yml

will output

    <cool id="hi">
      <foo>bar</foo>
    </cool>

  Encode value as xml string on a single line

Given a sample.yml file of:

    a:
      cool:
        foo: bar
        +@id: hi

then

    yq '.a | @xml' sample.yml

will output

    <cool id="hi"><foo>bar</foo></cool>

  Encode value as xml string with custom indentation

Given a sample.yml file of:

    a:
      cool:
        foo: bar
        +@id: hi

then

    yq '{"cat": .a | to_xml(1)}' sample.yml

will output

    cat: |
      <cool id="hi">
       <foo>bar</foo>
      </cool>

  Decode a xml encoded string

Given a sample.yml file of:

    a: <foo>bar</foo>

then

    yq '.b = (.a | from_xml)' sample.yml

will output

    a: <foo>bar</foo>
    b:
      foo: bar

  Encode a string to base64

Given a sample.yml file of:

    coolData: a special string

then

    yq '.coolData | @base64' sample.yml

will output

    YSBzcGVjaWFsIHN0cmluZw==

  Encode a yaml document to base64

Pipe through @yaml first to convert to a string, then use @base64 to encode it.

Given a sample.yml file of:

    a: apple

then

    yq '@yaml | @base64' sample.yml

will output

    YTogYXBwbGUK

  Encode a string to uri

Given a sample.yml file of:

    coolData: this has & special () characters *

then

    yq '.coolData | @uri' sample.yml

will output

    this+has+%26+special+%28%29+characters+%2A

  Decode a URI to a string

Given a sample.yml file of:

    this+has+%26+special+%28%29+characters+%2A

then

    yq '@urid' sample.yml

will output

    this has & special () characters *

  Encode a string to sh

Sh/Bash friendly string

Given a sample.yml file of:

    coolData: strings with spaces and a 'quote'

then

    yq '.coolData | @sh' sample.yml

will output

    strings' with spaces and a '\'quote\'

  Decode a base64 encoded string

Decoded data is assumed to be a string.

Given a sample.yml file of:

    coolData: V29ya3Mgd2l0aCBVVEYtMTYg8J+Yig==

then

    yq '.coolData | @base64d' sample.yml

will output

    Works with UTF-16 😊

  Decode a base64 encoded yaml document

Pipe through from_yaml to parse the decoded base64 string as a yaml document.

Given a sample.yml file of:

    coolData: YTogYXBwbGUK

then

    yq '.coolData |= (@base64d | from_yaml)' sample.yml

will output

    coolData:
      a: apple

Entries

Similar to the same named functions in jq these functions convert to/from an object and an array of key-value pairs. This is most useful for performing operations on keys of maps.

Use with_entries(op) as a syntactic sugar for doing to_entries | op | from_entries.

  to_entries Map

Given a sample.yml file of:

    a: 1
    b: 2

then

    yq 'to_entries' sample.yml

will output

    - key: a
      value: 1
    - key: b
      value: 2

  to_entries Array

Given a sample.yml file of:

    - a
    - b

then

    yq 'to_entries' sample.yml

will output

    - key: 0
      value: a
    - key: 1
      value: b

  to_entries null

Given a sample.yml file of:

    null

then

    yq 'to_entries' sample.yml

will output

  from_entries map

Given a sample.yml file of:

    a: 1
    b: 2

then

    yq 'to_entries | from_entries' sample.yml

will output

    a: 1
    b: 2

  from_entries with numeric key indices

from_entries always creates a map, even for numeric keys

Given a sample.yml file of:

    - a
    - b

then

    yq 'to_entries | from_entries' sample.yml

will output

    0: a
    1: b

  Use with_entries to update keys

Given a sample.yml file of:

    a: 1
    b: 2

then

    yq 'with_entries(.key |= "KEY_" + .)' sample.yml

will output

    KEY_a: 1
    KEY_b: 2

  Use with_entries to update keys recursively

We use (.. | select(tag=“map”)) to find all the maps in the doc, then |= to update each one of those maps. In the update, with_entries is used.

Given a sample.yml file of:

    a: 1
    b:
      b_a: nested
      b_b: thing

then

    yq '(.. | select(tag=="!!map")) |= with_entries(.key |= "KEY_" + .)' sample.yml

will output

    KEY_a: 1
    KEY_b:
      KEY_b_a: nested
      KEY_b_b: thing

  Custom sort map keys

Use to_entries to convert to an array of key/value pairs, sort the array using sort/sort_by/etc, and convert it back.

Given a sample.yml file of:

    a: 1
    c: 3
    b: 2

then

    yq 'to_entries | sort_by(.key) | reverse | from_entries' sample.yml

will output

    c: 3
    b: 2
    a: 1

  Use with_entries to filter the map

Given a sample.yml file of:

    a:
      b: bird
    c:
      d: dog

then

    yq 'with_entries(select(.value | has("b")))' sample.yml

will output

    a:
      b: bird

Env Variable Operators

These operators are used to handle environment variables usage in expressions and documents. While environment variables can, of course, be passed in via your CLI with string interpolation, this often comes with complex quote escaping and can be tricky to write and read.

There are three operators:

•   env which takes a single environment variable name and parse the variable as a yaml node (be it a map, array, string, number of boolean)

•   strenv which also takes a single environment variable name, and always parses the variable as a string.

•   envsubst which you pipe strings into and it interpolates environment variables in strings using envsubst (https://github.com/a8m/envsubst).

  EnvSubst Options

You can optionally pass envsubst any of the following options:

•   nu: NoUnset, this will fail if there are any referenced variables that are not set

•   ne: NoEmpty, this will fail if there are any referenced variables that are empty

•   ff: FailFast, this will abort on the first failure (rather than collect all the errors)

E.g: envsubst(ne, ff) will fail on the first empty variable.

See Imposing Restrictions (https://github.com/a8m/envsubst#imposing-restrictions) in the envsubst documentation for more information, and below for examples.

  Tip

To replace environment variables across all values in a document, envsubst can be used with the recursive descent operator as follows:

    yq '(.. | select(tag == "!!str")) |= envsubst' file.yaml

  Disabling env operators

If required, you can use the --security-disable-env-ops to disable env operations.

  Read string environment variable

Running

    myenv="cat meow" yq --null-input '.a = env(myenv)'

will output

    a: cat meow

  Read boolean environment variable

Running

    myenv="true" yq --null-input '.a = env(myenv)'

will output

    a: true

  Read numeric environment variable

Running

    myenv="12" yq --null-input '.a = env(myenv)'

will output

    a: 12

  Read yaml environment variable

Running

    myenv="{b: fish}" yq --null-input '.a = env(myenv)'

will output

    a: {b: fish}

  Read boolean environment variable as a string

Running

    myenv="true" yq --null-input '.a = strenv(myenv)'

will output

    a: "true"

  Read numeric environment variable as a string

Running

    myenv="12" yq --null-input '.a = strenv(myenv)'

will output

    a: "12"

  Dynamically update a path from an environment variable

The env variable can be any valid yq expression.

Given a sample.yml file of:

    a:
      b:
        - name: dog
        - name: cat

then

    pathEnv=".a.b[0].name"  valueEnv="moo" yq 'eval(strenv(pathEnv)) = strenv(valueEnv)' sample.yml

will output

    a:
      b:
        - name: moo
        - name: cat

  Dynamic key lookup with environment variable

Given a sample.yml file of:

    cat: meow
    dog: woof

then

    myenv="cat" yq '.[env(myenv)]' sample.yml

will output

    meow

  Replace strings with envsubst

Running

    myenv="cat" yq --null-input '"the ${myenv} meows" | envsubst'

will output

    the cat meows

  Replace strings with envsubst, missing variables

Running

    yq --null-input '"the ${myenvnonexisting} meows" | envsubst'

will output

    the  meows

  Replace strings with envsubst(nu), missing variables

(nu) not unset, will fail if there are unset (missing) variables

Running

    yq --null-input '"the ${myenvnonexisting} meows" | envsubst(nu)'

will output

    Error: variable ${myenvnonexisting} not set

  Replace strings with envsubst(ne), missing variables

(ne) not empty, only validates set variables

Running

    yq --null-input '"the ${myenvnonexisting} meows" | envsubst(ne)'

will output

    the  meows

  Replace strings with envsubst(ne), empty variable

(ne) not empty, will fail if a references variable is empty

Running

    myenv="" yq --null-input '"the ${myenv} meows" | envsubst(ne)'

will output

    Error: variable ${myenv} set but empty

  Replace strings with envsubst, missing variables with defaults

Running

    yq --null-input '"the ${myenvnonexisting-dog} meows" | envsubst'

will output

    the dog meows

  Replace strings with envsubst(nu), missing variables with defaults

Having a default specified skips over the missing variable.

Running

    yq --null-input '"the ${myenvnonexisting-dog} meows" | envsubst(nu)'

will output

    the dog meows

  Replace strings with envsubst(ne), missing variables with defaults

Fails, because the variable is explicitly set to blank.

Running

    myEmptyEnv="" yq --null-input '"the ${myEmptyEnv-dog} meows" | envsubst(ne)'

will output

    Error: variable ${myEmptyEnv} set but empty

  Replace string environment variable in document

Given a sample.yml file of:

    v: ${myenv}

then

    myenv="cat meow" yq '.v |= envsubst' sample.yml

will output

    v: cat meow

  (Default) Return all envsubst errors

By default, all errors are returned at once.

Running

    yq --null-input '"the ${notThere} ${alsoNotThere}" | envsubst(nu)'

will output

    Error: variable ${notThere} not set
    variable ${alsoNotThere} not set

  Fail fast, return the first envsubst error (and abort)

Running

    yq --null-input '"the ${notThere} ${alsoNotThere}" | envsubst(nu,ff)'

will output

    Error: variable ${notThere} not set

  env() operation fails when security is enabled

Use --security-disable-env-ops to disable env operations for security.

Running

    yq --null-input 'env("MYENV")'

will output

    Error: env operations have been disabled

  strenv() operation fails when security is enabled

Use --security-disable-env-ops to disable env operations for security.

Running

    yq --null-input 'strenv("MYENV")'

will output

    Error: env operations have been disabled

  envsubst() operation fails when security is enabled

Use --security-disable-env-ops to disable env operations for security.

Running

    yq --null-input '"value: ${MYENV}" | envsubst'

will output

    Error: env operations have been disabled

Equals / Not Equals

This is a boolean operator that will return true if the LHS is equal to the RHS and false otherwise.

    .a == .b

It is most often used with the select operator to find particular nodes:

    select(.a == .b)

The not equals != operator returns false if the LHS is equal to the RHS.

  Related Operators

•   comparison (>=, < etc) operators here (https://mikefarah.gitbook.io/yq/operators/compare)

•   boolean operators (and, or, any etc) here (https://mikefarah.gitbook.io/yq/operators/boolean-operators)

•   select operator here (https://mikefarah.gitbook.io/yq/operators/select)

  Match string

Given a sample.yml file of:

    - cat
    - goat
    - dog

then

    yq '.[] | (. == "*at")' sample.yml

will output

    true
    true
    false

  Don’t match string

Given a sample.yml file of:

    - cat
    - goat
    - dog

then

    yq '.[] | (. != "*at")' sample.yml

will output

    false
    false
    true

  Match number

Given a sample.yml file of:

    - 3
    - 4
    - 5

then

    yq '.[] | (. == 4)' sample.yml

will output

    false
    true
    false

  Don’t match number

Given a sample.yml file of:

    - 3
    - 4
    - 5

then

    yq '.[] | (. != 4)' sample.yml

will output

    true
    false
    true

  Match nulls

Running

    yq --null-input 'null == ~'

will output

    true

  Non existent key doesn’t equal a value

Given a sample.yml file of:

    a: frog

then

    yq 'select(.b != "thing")' sample.yml

will output

    a: frog

  Two non existent keys are equal

Given a sample.yml file of:

    a: frog

then

    yq 'select(.b == .c)' sample.yml

will output

    a: frog

Error

Use this operation to short-circuit expressions. Useful for validation.

  Validate a particular value

Given a sample.yml file of:

    a: hello

then

    yq 'select(.a == "howdy") or error(".a [" + .a + "] is not howdy!")' sample.yml

will output

    Error: .a [hello] is not howdy!

  Validate the environment variable is a number - invalid

Running

    numberOfCats="please" yq --null-input 'env(numberOfCats) | select(tag == "!!int") or error("numberOfCats is not a number :(")'

will output

    Error: numberOfCats is not a number :(

  Validate the environment variable is a number - valid

with can be a convenient way of encapsulating validation.

Given a sample.yml file of:

    name: Bob
    favouriteAnimal: cat

then

    numberOfCats="3" yq '
        with(env(numberOfCats); select(tag == "!!int") or error("numberOfCats is not a number :(")) |
        .numPets = env(numberOfCats)
    ' sample.yml

will output

    name: Bob
    favouriteAnimal: cat
    numPets: 3

Eval

Use eval to dynamically process an expression - for instance from an environment variable.

eval takes a single argument, and evaluates that as a yq expression. Any valid expression can be used, be it a path .a.b.c | select(. == "cat"), or an update .a.b.c = "gogo".

Tip: This can be a useful way to parameterise complex scripts.

  Dynamically evaluate a path

Given a sample.yml file of:

    pathExp: .a.b[] | select(.name == "cat")
    a:
      b:
        - name: dog
        - name: cat

then

    yq 'eval(.pathExp)' sample.yml

will output

    name: cat

  Dynamically update a path from an environment variable

The env variable can be any valid yq expression.

Given a sample.yml file of:

    a:
      b:
        - name: dog
        - name: cat

then

    pathEnv=".a.b[0].name"  valueEnv="moo" yq 'eval(strenv(pathEnv)) = strenv(valueEnv)' sample.yml

will output

    a:
      b:
        - name: moo
        - name: cat

File Operators

File operators are most often used with merge when needing to merge specific files together. Note that when doing this, you will need to use eval-all to ensure all yaml documents are loaded into memory before performing the merge (as opposed to eval which runs the expression once per document).

Note that the fileIndex operator has a short alias of fi.

  Merging files

Note the use of eval-all to ensure all documents are loaded into memory.

    yq eval-all 'select(fi == 0) * select(filename == "file2.yaml")' file1.yaml file2.yaml

  Get filename

Given a sample.yml file of:

    a: cat

then

    yq 'filename' sample.yml

will output

    sample.yml

  Get file index

Given a sample.yml file of:

    a: cat

then

    yq 'file_index' sample.yml

will output

    0

  Get file indices of multiple documents

Given a sample.yml file of:

    a: cat

And another sample another.yml file of:

    a: cat

then

    yq eval-all 'file_index' sample.yml another.yml

will output

    0
    1

  Get file index alias

Given a sample.yml file of:

    a: cat

then

    yq 'fi' sample.yml

will output

    0

Filter

Filters an array (or map values) by the expression given. Equivalent to doing map(select(exp)).

  Filter array

Given a sample.yml file of:

    - 1
    - 2
    - 3

then

    yq 'filter(. < 3)' sample.yml

will output

    - 1
    - 2

  Filter map values

Given a sample.yml file of:

    c:
      things: cool
      frog: yes
    d:
      things: hot
      frog: false

then

    yq 'filter(.things == "cool")' sample.yml

will output

    - things: cool
      frog: yes

First

Returns the first matching element in an array, or first matching value in a map.

Can be given an expression to match with, otherwise will just return the first.

  First matching element from array

Given a sample.yml file of:

    - a: banana
    - a: cat
    - a: apple

then

    yq 'first(.a == "cat")' sample.yml

will output

    a: cat

  First matching element from array with multiple matches

Given a sample.yml file of:

    - a: banana
    - a: cat
      b: firstCat
    - a: apple
    - a: cat
      b: secondCat

then

    yq 'first(.a == "cat")' sample.yml

will output

    a: cat
    b: firstCat

  First matching element from array with numeric condition

Given a sample.yml file of:

    - a: 10
    - a: 100
    - a: 1
    - a: 101

then

    yq 'first(.a > 50)' sample.yml

will output

    a: 100

  First matching element from array with boolean condition

Given a sample.yml file of:

    - a: false
    - a: true
      b: firstTrue
    - a: false
    - a: true
      b: secondTrue

then

    yq 'first(.a == true)' sample.yml

will output

    a: true
    b: firstTrue

  First matching element from array with null values

Given a sample.yml file of:

    - a: null
    - a: cat
    - a: apple

then

    yq 'first(.a != null)' sample.yml

will output

    a: cat

  First matching element from array with complex condition

Given a sample.yml file of:

    - a: dog
      b: 7
    - a: cat
      b: 3
    - a: apple
      b: 5

then

    yq 'first(.b > 4 and .b < 6)' sample.yml

will output

    a: apple
    b: 5

  First matching element from map

Given a sample.yml file of:

    x:
      a: banana
    y:
      a: cat
    z:
      a: apple

then

    yq 'first(.a == "cat")' sample.yml

will output

    a: cat

  First matching element from map with numeric condition

Given a sample.yml file of:

    x:
      a: 10
    y:
      a: 100
    z:
      a: 101

then

    yq 'first(.a > 50)' sample.yml

will output

    a: 100

  First matching element from nested structure

Given a sample.yml file of:

    items:
      - a: banana
      - a: cat
      - a: apple

then

    yq '.items | first(.a == "cat")' sample.yml

will output

    a: cat

  First matching element with no matches

Given a sample.yml file of:

    - a: banana
    - a: cat
    - a: apple

then

    yq 'first(.a == "dog")' sample.yml

will output

  First matching element from empty array

Given a sample.yml file of:

    []

then

    yq 'first(.a == "cat")' sample.yml

will output

  First matching element from scalar node

Given a sample.yml file of:

    hello

then

    yq 'first(. == "hello")' sample.yml

will output

  First matching element from null node

Given a sample.yml file of:

    null

then

    yq 'first(. == "hello")' sample.yml

will output

  First matching element with string condition

Given a sample.yml file of:

    - a: banana
    - a: cat
    - a: apple

then

    yq 'first(.a | test("^c"))' sample.yml

will output

    a: cat

  First matching element with length condition

Given a sample.yml file of:

    - a: hi
    - a: hello
    - a: world

then

    yq 'first(.a | length > 4)' sample.yml

will output

    a: hello

  First matching element from array of strings

Given a sample.yml file of:

    - banana
    - cat
    - apple

then

    yq 'first(. == "cat")' sample.yml

will output

    cat

  First matching element from array of numbers

Given a sample.yml file of:

    - 10
    - 100
    - 1

then

    yq 'first(. > 50)' sample.yml

will output

    100

  First element with no filter from array

Given a sample.yml file of:

    - 10
    - 100
    - 1

then

    yq 'first' sample.yml

will output

    10

  First element with no filter from array of maps

Given a sample.yml file of:

    - a: 10
    - a: 100

then

    yq 'first' sample.yml

will output

    a: 10

Flatten

This recursively flattens arrays.

  Flatten

Recursively flattens all arrays

Given a sample.yml file of:

    - 1
    - - 2
    - - - 3

then

    yq 'flatten' sample.yml

will output

    - 1
    - 2
    - 3

  Flatten with depth of one

Given a sample.yml file of:

    - 1
    - - 2
    - - - 3

then

    yq 'flatten(1)' sample.yml

will output

    - 1
    - 2
    - - 3

  Flatten empty array

Given a sample.yml file of:

    - []

then

    yq 'flatten' sample.yml

will output

    []

  Flatten array of objects

Given a sample.yml file of:

    - foo: bar
    - - foo: baz

then

    yq 'flatten' sample.yml

will output

    - foo: bar
    - foo: baz

Group By

This is used to group items in an array by an expression.

  Group by field

Given a sample.yml file of:

    - foo: 1
      bar: 10
    - foo: 3
      bar: 100
    - foo: 1
      bar: 1

then

    yq 'group_by(.foo)' sample.yml

will output

    - - foo: 1
        bar: 10
      - foo: 1
        bar: 1
    - - foo: 3
        bar: 100

  Group by field, with nulls

Given a sample.yml file of:

    - cat: dog
    - foo: 1
      bar: 10
    - foo: 3
      bar: 100
    - no: foo for you
    - foo: 1
      bar: 1

then

    yq 'group_by(.foo)' sample.yml

will output

    - - cat: dog
      - no: foo for you
    - - foo: 1
        bar: 10
      - foo: 1
        bar: 1
    - - foo: 3
        bar: 100

Has

This operation returns true if the key exists in a map (or index in an array), false otherwise.

  Has map key

Given a sample.yml file of:

    - a: yes
    - a: ~
    - a:
    - b: nope

then

    yq '.[] | has("a")' sample.yml

will output

    true
    true
    true
    false

  Select, checking for existence of deep paths

Simply pipe in parent expressions into has

Given a sample.yml file of:

    - a:
        b:
          c: cat
    - a:
        b:
          d: dog

then

    yq '.[] | select(.a.b | has("c"))' sample.yml

will output

    a:
      b:
        c: cat

  Has array index

Given a sample.yml file of:

    - []
    - [1]
    - [1, 2]
    - [1, null]
    - [1, 2, 3]

then

    yq '.[] | has(1)' sample.yml

will output

    false
    false
    true
    true
    true

Keys

Use the keys operator to return map keys or array indices.

  Map keys

Given a sample.yml file of:

    dog: woof
    cat: meow

then

    yq 'keys' sample.yml

will output

    - dog
    - cat

  Array keys

Given a sample.yml file of:

    - apple
    - banana

then

    yq 'keys' sample.yml

will output

    - 0
    - 1

  Retrieve array key

Given a sample.yml file of:

    - 1
    - 2
    - 3

then

    yq '.[1] | key' sample.yml

will output

    1

  Retrieve map key

Given a sample.yml file of:

    a: thing

then

    yq '.a | key' sample.yml

will output

    a

  No key

Given a sample.yml file of:

    {}

then

    yq 'key' sample.yml

will output

  Update map key

Given a sample.yml file of:

    a:
      x: 3
      y: 4

then

    yq '(.a.x | key) = "meow"' sample.yml

will output

    a:
      meow: 3
      y: 4

  Get comment from map key

Given a sample.yml file of:

    a:
      # comment on key
      x: 3
      y: 4

then

    yq '.a.x | key | headComment' sample.yml

will output

    comment on key

  Check node is a key

Given a sample.yml file of:

    a:
      b:
        - cat
      c: frog

then

    yq '[... | { "p": path | join("."), "isKey": is_key, "tag": tag }]' sample.yml

will output

    - p: ""
      isKey: false
      tag: '!!map'
    - p: a
      isKey: true
      tag: '!!str'
    - p: a
      isKey: false
      tag: '!!map'
    - p: a.b
      isKey: true
      tag: '!!str'
    - p: a.b
      isKey: false
      tag: '!!seq'
    - p: a.b.0
      isKey: false
      tag: '!!str'
    - p: a.c
      isKey: true
      tag: '!!str'
    - p: a.c
      isKey: false
      tag: '!!str'

Kind

The kind operator identifies the type of a node as either scalar, map, or seq.

This can be used for filtering or transforming nodes based on their type.

Note that null values are treated as scalar.

  Get kind

Given a sample.yml file of:

    a: cat
    b: 5
    c: 3.2
    e: true
    f: []
    g: {}
    h: null

then

    yq '.. | kind' sample.yml

will output

    map
    scalar
    scalar
    scalar
    scalar
    seq
    map
    scalar

  Get kind, ignores custom tags

Unlike tag, kind is not affected by custom tags.

Given a sample.yml file of:

    a: !!thing cat
    b: !!foo {}
    c: !!bar []

then

    yq '.. | kind' sample.yml

will output

    map
    scalar
    map
    seq

  Add comments only to scalars

An example of how you can use kind

Given a sample.yml file of:

    a:
      b: 5
      c: 3.2
    e: true
    f: []
    g: {}
    h: null

then

    yq '(.. | select(kind == "scalar")) line_comment = "this is a scalar"' sample.yml

will output

    a:
      b: 5 # this is a scalar
      c: 3.2 # this is a scalar
    e: true # this is a scalar
    f: []
    g: {}
    h: null # this is a scalar

Length

Returns the lengths of the nodes. Length is defined according to the type of the node.

  String length

returns length of string

Given a sample.yml file of:

    a: cat

then

    yq '.a | length' sample.yml

will output

    3

  null length

Given a sample.yml file of:

    a: null

then

    yq '.a | length' sample.yml

will output

    0

  Map length

returns number of entries

Given a sample.yml file of:

    a: cat
    c: dog

then

    yq 'length' sample.yml

will output

    2

  Array length

returns number of elements

Given a sample.yml file of:

    - 2
    - 4
    - 6
    - 8

then

    yq 'length' sample.yml

will output

    4

Line

Returns the line of the matching node. Starts from 1, 0 indicates there was no line data.

  Returns line of value node

Given a sample.yml file of:

    a: cat
    b:
      c: cat

then

    yq '.b | line' sample.yml

will output

    3

  Returns line of key node

Pipe through the key operator to get the line of the key

Given a sample.yml file of:

    a: cat
    b:
      c: cat

then

    yq '.b | key | line' sample.yml

will output

    2

  First line is 1

Given a sample.yml file of:

    a: cat

then

    yq '.a | line' sample.yml

will output

    1

  No line data is 0

Running

    yq --null-input '{"a": "new entry"} | line'

will output

    0

Load

The load operators allows you to load in content from another file.

Note that you can use string operators like + and sub to modify the value in the yaml file to a path that exists in your system.

You can load files of the following supported types:

Format | Load Operator
Yaml | load
XML | load_xml
Properties | load_props
Plain String | load_str
Base64 | load_base64

Note that load_base64 only works for base64 encoded utf-8 strings.

  Samples files for tests:

  yaml

../../examples/thing.yml:

    a: apple is included
    b: cool

  xml

small.xml:

    <this>is some xml</this>

  properties

small.properties:

    this.is = a properties file

  base64

base64.txt:

    bXkgc2VjcmV0IGNoaWxsaSByZWNpcGUgaXMuLi4u

  Disabling file operators

If required, you can use the --security-disable-file-ops to disable file operations.

  Simple example

Given a sample.yml file of:

    myFile: ../../examples/thing.yml

then

    yq 'load(.myFile)' sample.yml

will output

    a: apple is included
    b: cool.

  Replace node with referenced file

Note that you can modify the filename in the load operator if needed.

Given a sample.yml file of:

    something:
      file: thing.yml

then

    yq '.something |= load("../../examples/" + .file)' sample.yml

will output

    something:
      a: apple is included
      b: cool.

  Replace all nodes with referenced file

Recursively match all the nodes (..) and then filter the ones that have a `file' attribute.

Given a sample.yml file of:

    something:
      file: thing.yml
    over:
      here:
        - file: thing.yml

then

    yq '(.. | select(has("file"))) |= load("../../examples/" + .file)' sample.yml

will output

    something:
      a: apple is included
      b: cool.
    over:
      here:
        - a: apple is included
          b: cool.

  Replace node with referenced file as string

This will work for any text based file

Given a sample.yml file of:

    something:
      file: thing.yml

then

    yq '.something |= load_str("../../examples/" + .file)' sample.yml

will output

    something: |-
      a: apple is included
      b: cool.

  Load from XML

Given a sample.yml file of:

    cool: things

then

    yq '.more_stuff = load_xml("../../examples/small.xml")' sample.yml

will output

    cool: things
    more_stuff:
      this: is some xml

  Load from Properties

Given a sample.yml file of:

    cool: things

then

    yq '.more_stuff = load_props("../../examples/small.properties")' sample.yml

will output

    cool: things
    more_stuff:
      this:
        is: a properties file

  Merge from properties

This can be used as a convenient way to update a yaml document

Given a sample.yml file of:

    this:
      is: from yaml
      cool: ay

then

    yq '. *= load_props("../../examples/small.properties")' sample.yml

will output

    this:
      is: a properties file
      cool: ay

  Load from base64 encoded file

Given a sample.yml file of:

    cool: things

then

    yq '.more_stuff = load_base64("../../examples/base64.txt")' sample.yml

will output

    cool: things
    more_stuff: my secret chilli recipe is....

  load() operation fails when security is enabled

Use --security-disable-file-ops to disable file operations for security.

Running

    yq --null-input 'load("../../examples/thing.yml")'

will output

    Error: file operations have been disabled

  load_str() operation fails when security is enabled

Use --security-disable-file-ops to disable file operations for security.

Running

    yq --null-input 'load_str("../../examples/thing.yml")'

will output

    Error: file operations have been disabled

  load_xml() operation fails when security is enabled

Use --security-disable-file-ops to disable file operations for security.

Running

    yq --null-input 'load_xml("../../examples/small.xml")'

will output

    Error: file operations have been disabled

  load_props() operation fails when security is enabled

Use --security-disable-file-ops to disable file operations for security.

Running

    yq --null-input 'load_props("../../examples/small.properties")'

will output

    Error: file operations have been disabled

  load_base64() operation fails when security is enabled

Use --security-disable-file-ops to disable file operations for security.

Running

    yq --null-input 'load_base64("../../examples/base64.txt")'

will output

    Error: file operations have been disabled

Map

Maps values of an array. Use map_values to map values of an object.

  Map array

Given a sample.yml file of:

    - 1
    - 2
    - 3

then

    yq 'map(. + 1)' sample.yml

will output

    - 2
    - 3
    - 4

  Map object values

Given a sample.yml file of:

    a: 1
    b: 2
    c: 3

then

    yq 'map_values(. + 1)' sample.yml

will output

    a: 2
    b: 3
    c: 4

Max

Computes the maximum among an incoming sequence of scalar values.

  Maximum int

Given a sample.yml file of:

    - 99
    - 16
    - 12
    - 6
    - 66

then

    yq 'max' sample.yml

will output

    99

  Maximum string

Given a sample.yml file of:

    - foo
    - bar
    - baz

then

    yq 'max' sample.yml

will output

    foo

  Maximum of empty

Given a sample.yml file of:

    []

then

    yq 'max' sample.yml

will output

Min

Computes the minimum among an incoming sequence of scalar values.

  Minimum int

Given a sample.yml file of:

    - 99
    - 16
    - 12
    - 6
    - 66

then

    yq 'min' sample.yml

will output

    6

  Minimum string

Given a sample.yml file of:

    - foo
    - bar
    - baz

then

    yq 'min' sample.yml

will output

    bar

  Minimum of empty

Given a sample.yml file of:

    []

then

    yq 'min' sample.yml

will output

Modulo

Arithmetic modulo operator, returns the remainder from dividing two numbers.

  Number modulo - int

If the lhs and rhs are ints then the expression will be calculated with ints.

Given a sample.yml file of:

    a: 13
    b: 2

then

    yq '.a = .a % .b' sample.yml

will output

    a: 1
    b: 2

  Number modulo - float

If the lhs or rhs are floats then the expression will be calculated with floats.

Given a sample.yml file of:

    a: 12
    b: 2.5

then

    yq '.a = .a % .b' sample.yml

will output

    a: !!float 2
    b: 2.5

  Number modulo - int by zero

If the lhs is an int and rhs is a 0 the result is an error.

Given a sample.yml file of:

    a: 1
    b: 0

then

    yq '.a = .a % .b' sample.yml

will output

    Error: cannot modulo by 0

  Number modulo - float by zero

If the lhs is a float and rhs is a 0 the result is NaN.

Given a sample.yml file of:

    a: 1.1
    b: 0

then

    yq '.a = .a % .b' sample.yml

will output

    a: !!float NaN
    b: 0

Multiply (Merge)

Like the multiple operator in jq, depending on the operands, this multiply operator will do different things. Currently numbers, arrays and objects are supported.

  Objects and arrays - merging

Objects are merged deeply matching on matching keys. By default, array values override and are not deeply merged.

You can use the add operator +, to shallow merge objects, see more info here (https://mikefarah.gitbook.io/yq/operators/add).

Note that when merging objects, this operator returns the merged object (not the parent). This will be clearer in the examples below.

  Merge Flags

You can control how objects are merged by using one or more of the following flags. Multiple flags can be used together, e.g. .a *+? .b. See examples below

•   + append arrays

•   d deeply merge arrays

•   ? only merge existing fields

•   n only merge new fields

•   c clobber custom tags

To perform a shallow merge only, use the add operator +, see more info here (https://mikefarah.gitbook.io/yq/operators/add).

  Merge two files together

This uses the load operator to merge file2 into file1.

    yq '. *= load("file2.yml")' file1.yml

  Merging all files

Note the use of eval-all to ensure all documents are loaded into memory.

    yq eval-all '. as $item ireduce ({}; . * $item )' *.yml

Merging complex arrays together by a key field

By default - yq merge is naive. It merges maps when they match the key name, and arrays are merged either by appending them together, or merging the entries by their position in the array.

For more complex array merging (e.g. merging items that match on a certain key) please see the example here (https://mikefarah.gitbook.io/yq/operators/multiply-merge#merge-arrays-of-objects-together-matching-on-a-key)

  Multiply integers

Given a sample.yml file of:

    a: 3
    b: 4

then

    yq '.a *= .b' sample.yml

will output

    a: 12
    b: 4

  Multiply string node X int

Given a sample.yml file of:

    b: banana

then

    yq '.b * 4' sample.yml

will output

    bananabananabananabanana

  Multiply int X string node

Given a sample.yml file of:

    b: banana

then

    yq '4 * .b' sample.yml

will output

    bananabananabananabanana

  Multiply string X int node

Given a sample.yml file of:

    n: 4

then

    yq '"banana" * .n' sample.yml

will output

    bananabananabananabanana

  Multiply int node X string

Given a sample.yml file of:

    n: 4

then

    yq '.n * "banana"' sample.yml

will output

    bananabananabananabanana

  Merge objects together, returning merged result only

Given a sample.yml file of:

    a:
      field: me
      fieldA: cat
    b:
      field:
        g: wizz
      fieldB: dog

then

    yq '.a * .b' sample.yml

will output

    field:
      g: wizz
    fieldA: cat
    fieldB: dog

  Merge objects together, returning parent object

Given a sample.yml file of:

    a:
      field: me
      fieldA: cat
    b:
      field:
        g: wizz
      fieldB: dog

then

    yq '. * {"a":.b}' sample.yml

will output

    a:
      field:
        g: wizz
      fieldA: cat
      fieldB: dog
    b:
      field:
        g: wizz
      fieldB: dog

  Merge keeps style of LHS

Given a sample.yml file of:

    a: {things: great}
    b:
      also: "me"

then

    yq '. * {"a":.b}' sample.yml

will output

    a: {things: great, also: "me"}
    b:
      also: "me"

  Merge arrays

Given a sample.yml file of:

    a:
      - 1
      - 2
      - 3
    b:
      - 3
      - 4
      - 5

then

    yq '. * {"a":.b}' sample.yml

will output

    a:
      - 3
      - 4
      - 5
    b:
      - 3
      - 4
      - 5

  Merge, only existing fields

Given a sample.yml file of:

    a:
      thing: one
      cat: frog
    b:
      missing: two
      thing: two

then

    yq '.a *? .b' sample.yml

will output

    thing: two
    cat: frog

  Merge, only new fields

Given a sample.yml file of:

    a:
      thing: one
      cat: frog
    b:
      missing: two
      thing: two

then

    yq '.a *n .b' sample.yml

will output

    thing: one
    cat: frog
    missing: two

  Merge, appending arrays

Given a sample.yml file of:

    a:
      array:
        - 1
        - 2
        - animal: dog
      value: coconut
    b:
      array:
        - 3
        - 4
        - animal: cat
      value: banana

then

    yq '.a *+ .b' sample.yml

will output

    array:
      - 1
      - 2
      - animal: dog
      - 3
      - 4
      - animal: cat
    value: banana

  Merge, only existing fields, appending arrays

Given a sample.yml file of:

    a:
      thing:
        - 1
        - 2
    b:
      thing:
        - 3
        - 4
      another:
        - 1

then

    yq '.a *?+ .b' sample.yml

will output

    thing:
      - 1
      - 2
      - 3
      - 4

  Merge, deeply merging arrays

Merging arrays deeply means arrays are merged like objects, with indices as their key. In this case, we merge the first item in the array and do nothing with the second.

Given a sample.yml file of:

    a:
      - name: fred
        age: 12
      - name: bob
        age: 32
    b:
      - name: fred
        age: 34

then

    yq '.a *d .b' sample.yml

will output

    - name: fred
      age: 34
    - name: bob
      age: 32

  Merge arrays of objects together, matching on a key

This is a fairly complex expression - you can use it as is by providing the environment variables as seen in the example below.

It merges in the array provided in the second file into the first - matching on equal keys.

Explanation:

The approach, at a high level, is to reduce into a merged map (keyed by the unique key) and then convert that back into an array.

First the expression will create a map from the arrays keyed by the idPath, the unique field we want to merge by. The reduce operator is merging `({}; . * $item )', so array elements with the matching key will be merged together.

Next, we convert the map back to an array, using reduce again, concatenating all the map values together.

Finally, we set the result of the merged array back into the first doc.

Thanks Kev from stackoverflow (https://stackoverflow.com/a/70109529/1168223)

Given a sample.yml file of:

    myArray:
      - a: apple
        b: appleB
      - a: kiwi
        b: kiwiB
      - a: banana
        b: bananaB
    something: else

And another sample another.yml file of:

    newArray:
      - a: banana
        c: bananaC
      - a: apple
        b: appleB2
      - a: dingo
        c: dingoC

then

    idPath=".a"  originalPath=".myArray"  otherPath=".newArray" yq eval-all '
    (
      (( (eval(strenv(originalPath)) + eval(strenv(otherPath)))  | .[] | {(eval(strenv(idPath))):  .}) as $item ireduce ({}; . * $item )) as $uniqueMap
      | ( $uniqueMap  | to_entries | .[]) as $item ireduce([]; . + $item.value)
    ) as $mergedArray
    | select(fi == 0) | (eval(strenv(originalPath))) = $mergedArray
    ' sample.yml another.yml

will output

    myArray:
      - a: apple
        b: appleB2
      - a: kiwi
        b: kiwiB
      - a: banana
        b: bananaB
        c: bananaC
      - a: dingo
        c: dingoC
    something: else

  Merge to prefix an element

Given a sample.yml file of:

    a: cat
    b: dog

then

    yq '. * {"a": {"c": .a}}' sample.yml

will output

    a:
      c: cat
    b: dog

  Merge with simple aliases

Given a sample.yml file of:

    a: &cat
      c: frog
    b:
      f: *cat
    c:
      g: thongs

then

    yq '.c * .b' sample.yml

will output

    g: thongs
    f: *cat

  Merge copies anchor names

Given a sample.yml file of:

    a:
      c: &cat frog
    b:
      f: *cat
    c:
      g: thongs

then

    yq '.c * .a' sample.yml

will output

    g: thongs
    c: &cat frog

  Merge with merge anchors

Given a sample.yml file of:

    foo: &foo
      a: foo_a
      thing: foo_thing
      c: foo_c
    bar: &bar
      b: bar_b
      thing: bar_thing
      c: bar_c
    foobarList:
      b: foobarList_b
      !!merge <<:
        - *foo
        - *bar
      c: foobarList_c
    foobar:
      c: foobar_c
      !!merge <<: *foo
      thing: foobar_thing

then

    yq '.foobar * .foobarList' sample.yml

will output

    c: foobarList_c
    !!merge <<:
      - *foo
      - *bar
    thing: foobar_thing
    b: foobarList_b

  Custom types: that are really numbers

When custom tags are encountered, yq will try to decode the underlying type.

Given a sample.yml file of:

    a: !horse 2
    b: !goat 3

then

    yq '.a = .a * .b' sample.yml

will output

    a: !horse 6
    b: !goat 3

  Custom types: that are really maps

Custom tags will be maintained.

Given a sample.yml file of:

    a: !horse
      cat: meow
    b: !goat
      dog: woof

then

    yq '.a = .a * .b' sample.yml

will output

    a: !horse
      cat: meow
      dog: woof
    b: !goat
      dog: woof

  Custom types: clobber tags

Use the c option to clobber custom tags. Note that the second tag is now used.

Given a sample.yml file of:

    a: !horse
      cat: meow
    b: !goat
      dog: woof

then

    yq '.a *=c .b' sample.yml

will output

    a: !goat
      cat: meow
      dog: woof
    b: !goat
      dog: woof

  Merging a null with a map

Running

    yq --null-input 'null * {"some": "thing"}'

will output

    some: thing

  Merging a map with null

Running

    yq --null-input '{"some": "thing"} * null'

will output

    some: thing

  Merging a null with an array

Running

    yq --null-input 'null * ["some"]'

will output

    - some

  Merging an array with null

Running

    yq --null-input '["some"] * null'

will output

    - some

Omit

Works like pick, but instead you specify the keys/indices that you don’t want included.

  Omit keys from map

Note that non existent keys are skipped.

Given a sample.yml file of:

    myMap:
      cat: meow
      dog: bark
      thing: hamster
      hamster: squeak

then

    yq '.myMap |= omit(["hamster", "cat", "goat"])' sample.yml

will output

    myMap:
      dog: bark
      thing: hamster

  Omit indices from array

Note that non existent indices are skipped.

Given a sample.yml file of:

    - cat
    - leopard
    - lion

then

    yq 'omit([2, 0, 734, -5])' sample.yml

will output

    - leopard

Parent

Parent simply returns the parent nodes of the matching nodes.

  Simple example

Given a sample.yml file of:

    a:
      nested: cat

then

    yq '.a.nested | parent' sample.yml

will output

    nested: cat

  Parent of nested matches

Given a sample.yml file of:

    a:
      fruit: apple
      name: bob
    b:
      fruit: banana
      name: sam

then

    yq '.. | select(. == "banana") | parent' sample.yml

will output

    fruit: banana
    name: sam

  Get parent attribute

Given a sample.yml file of:

    a:
      fruit: apple
      name: bob
    b:
      fruit: banana
      name: sam

then

    yq '.. | select(. == "banana") | parent.name' sample.yml

will output

    sam

  Get parents

Match all parents

Given a sample.yml file of:

    a:
      b:
        c: cat

then

    yq '.a.b.c | parents' sample.yml

will output

    - c: cat
    - b:
        c: cat
    - a:
        b:
          c: cat

  Get the top (root) parent

Use negative numbers to get the top parents. You can think of this as indexing into the `parents' array above

Given a sample.yml file of:

    a:
      b:
        c: cat

then

    yq '.a.b.c | parent(-1)' sample.yml

will output

    a:
      b:
        c: cat

  Root

Alias for parent(-1), returns the top level parent. This is usually the document node.

Given a sample.yml file of:

    a:
      b:
        c: cat

then

    yq '.a.b.c | root' sample.yml

will output

    a:
      b:
        c: cat

  N-th parent

You can optionally supply the number of levels to go up for the parent, the default being 1.

Given a sample.yml file of:

    a:
      b:
        c: cat

then

    yq '.a.b.c | parent(2)' sample.yml

will output

    b:
      c: cat

  N-th parent - another level

Given a sample.yml file of:

    a:
      b:
        c: cat

then

    yq '.a.b.c | parent(3)' sample.yml

will output

    a:
      b:
        c: cat

  N-th negative

Similarly, use negative numbers to index backwards from the parents array

Given a sample.yml file of:

    a:
      b:
        c: cat

then

    yq '.a.b.c | parent(-2)' sample.yml

will output

    b:
      c: cat

  No parent

Given a sample.yml file of:

    {}

then

    yq 'parent' sample.yml

will output

Path

The path operator can be used to get the traversal paths of matching nodes in an expression. The path is returned as an array, which if traversed in order will lead to the matching node.

You can get the key/index of matching nodes by using the path operator to return the path array then piping that through .[-1] to get the last element of that array, the key.

Use setpath to set a value to the path array returned by path, and similarly delpaths for an array of path arrays.

  Map path

Given a sample.yml file of:

    a:
      b: cat

then

    yq '.a.b | path' sample.yml

will output

    - a
    - b

  Get map key

Given a sample.yml file of:

    a:
      b: cat

then

    yq '.a.b | path | .[-1]' sample.yml

will output

    b

  Array path

Given a sample.yml file of:

    a:
      - cat
      - dog

then

    yq '.a.[] | select(. == "dog") | path' sample.yml

will output

    - a
    - 1

  Get array index

Given a sample.yml file of:

    a:
      - cat
      - dog

then

    yq '.a.[] | select(. == "dog") | path | .[-1]' sample.yml

will output

    1

  Print path and value

Given a sample.yml file of:

    a:
      - cat
      - dog
      - frog

then

    yq '.a[] | select(. == "*og") | [{"path":path, "value":.}]' sample.yml

will output

    - path:
        - a
        - 1
      value: dog
    - path:
        - a
        - 2
      value: frog

  Set path

Given a sample.yml file of:

    a:
      b: cat

then

    yq 'setpath(["a", "b"]; "things")' sample.yml

will output

    a:
      b: things

  Set on empty document

Running

    yq --null-input 'setpath(["a", "b"]; "things")'

will output

    a:
      b: things

  Set path to prune deep paths

Like pick but recursive. This uses ireduce to deeply set the selected paths into an empty object.

Given a sample.yml file of:

    parentA: bob
    parentB:
      child1: i am child1
      child2: i am child2
    parentC:
      child1: me child1
      child2: me child2

then

    yq '(.parentB.child2, .parentC.child1) as $i
      ireduce({}; setpath($i | path; $i))' sample.yml

will output

    parentB:
      child2: i am child2
    parentC:
      child1: me child1

  Set array path

Given a sample.yml file of:

    a:
      - cat
      - frog

then

    yq 'setpath(["a", 0]; "things")' sample.yml

will output

    a:
      - things
      - frog

  Set array path empty

Running

    yq --null-input 'setpath(["a", 0]; "things")'

will output

    a:
      - things

  Delete path

Notice delpaths takes an array of paths.

Given a sample.yml file of:

    a:
      b: cat
      c: dog
      d: frog

then

    yq 'delpaths([["a", "c"], ["a", "d"]])' sample.yml

will output

    a:
      b: cat

  Delete array path

Given a sample.yml file of:

    a:
      - cat
      - frog

then

    yq 'delpaths([["a", 0]])' sample.yml

will output

    a:
      - frog

  Delete - wrong parameter

delpaths does not work with a single path array

Given a sample.yml file of:

    a:
      - cat
      - frog

then

    yq 'delpaths(["a", 0])' sample.yml

will output

    Error: DELPATHS: expected entry [0] to be a sequence, but its a !!str. Note that delpaths takes an array of path arrays, e.g. [["a", "b"]]

Pick

Filter a map by the specified list of keys. Map is returned with the key in the order of the pick list.

Similarly, filter an array by the specified list of indices.

  Pick keys from map

Note that the order of the keys matches the pick order and non existent keys are skipped.

Given a sample.yml file of:

    myMap:
      cat: meow
      dog: bark
      thing: hamster
      hamster: squeak

then

    yq '.myMap |= pick(["hamster", "cat", "goat"])' sample.yml

will output

    myMap:
      hamster: squeak
      cat: meow

  Pick keys from map, included all the keys

We create a map of the picked keys plus all the current keys, and run that through unique

Given a sample.yml file of:

    myMap:
      cat: meow
      dog: bark
      thing: hamster
      hamster: squeak

then

    yq '.myMap |= pick( (["thing"] + keys) | unique)' sample.yml

will output

    myMap:
      thing: hamster
      cat: meow
      dog: bark
      hamster: squeak

  Pick indices from array

Note that the order of the indices matches the pick order and non existent indices are skipped.

Given a sample.yml file of:

    - cat
    - leopard
    - lion

then

    yq 'pick([2, 0, 734, -5])' sample.yml

will output

    - lion
    - cat

Pipe

Pipe the results of an expression into another. Like the bash operator.

  Simple Pipe

Given a sample.yml file of:

    a:
      b: cat

then

    yq '.a | .b' sample.yml

will output

    cat

  Multiple updates

Given a sample.yml file of:

    a: cow
    b: sheep
    c: same

then

    yq '.a = "cat" | .b = "dog"' sample.yml

will output

    a: cat
    b: dog
    c: same

Pivot

Emulates the PIVOT function supported by several popular RDBMS systems.

  Pivot a sequence of sequences

Given a sample.yml file of:

    - - foo
      - bar
      - baz
    - - sis
      - boom
      - bah

then

    yq 'pivot' sample.yml

will output

    - - foo
      - sis
    - - bar
      - boom
    - - baz
      - bah

  Pivot sequence of heterogeneous sequences

Missing values are “padded” to null.

Given a sample.yml file of:

    - - foo
      - bar
      - baz
    - - sis
      - boom
      - bah
      - blah

then

    yq 'pivot' sample.yml

will output

    - - foo
      - sis
    - - bar
      - boom
    - - baz
      - bah
    - -
      - blah

  Pivot sequence of maps

Given a sample.yml file of:

    - foo: a
      bar: b
      baz: c
    - foo: x
      bar: y
      baz: z

then

    yq 'pivot' sample.yml

will output

    foo:
      - a
      - x
    bar:
      - b
      - y
    baz:
      - c
      - z

  Pivot sequence of heterogeneous maps

Missing values are “padded” to null.

Given a sample.yml file of:

    - foo: a
      bar: b
      baz: c
    - foo: x
      bar: y
      baz: z
      what: ever

then

    yq 'pivot' sample.yml

will output

    foo:
      - a
      - x
    bar:
      - b
      - y
    baz:
      - c
      - z
    what:
      -
      - ever

Recursive Descent (Glob)

This operator recursively matches (or globs) all children nodes given of a particular element, including that node itself. This is most often used to apply a filter recursively against all matches.

  match values form ..

This will, like the jq equivalent, recursively match all value nodes. Use it to find/manipulate particular values.

For instance to set the style of all value nodes in a yaml doc, excluding map keys:

    yq '.. style= "flow"' file.yaml

  match values and map keys form ...

The also includes map keys in the results set. This is particularly useful in YAML as unlike JSON, map keys can have their own styling and tags and also use anchors and aliases.

For instance to set the style of all nodes in a yaml doc, including the map keys:

    yq '... style= "flow"' file.yaml

  Recurse map (values only)

Given a sample.yml file of:

    a: frog

then

    yq '..' sample.yml

will output

    a: frog
    frog

  Recursively find nodes with keys

Note that this example has wrapped the expression in [] to show that there are two matches returned. You do not have to wrap in [] in your path expression.

Given a sample.yml file of:

    a:
      name: frog
      b:
        name: blog
        age: 12

then

    yq '[.. | select(has("name"))]' sample.yml

will output

    - name: frog
      b:
        name: blog
        age: 12
    - name: blog
      age: 12

  Recursively find nodes with values

Given a sample.yml file of:

    a:
      nameA: frog
      b:
        nameB: frog
        age: 12

then

    yq '.. | select(. == "frog")' sample.yml

will output

    frog
    frog

  Recurse map (values and keys)

Note that the map key appears in the results

Given a sample.yml file of:

    a: frog

then

    yq '...' sample.yml

will output

    a: frog
    a
    frog

  Aliases are not traversed

Given a sample.yml file of:

    a: &cat
      c: frog
    b: *cat

then

    yq '[..]' sample.yml

will output

    - a: &cat
        c: frog
      b: *cat
    - &cat
      c: frog
    - frog
    - *cat

  Merge docs are not traversed

Given a sample.yml file of:

    foo: &foo
      a: foo_a
      thing: foo_thing
      c: foo_c
    bar: &bar
      b: bar_b
      thing: bar_thing
      c: bar_c
    foobarList:
      b: foobarList_b
      !!merge <<:
        - *foo
        - *bar
      c: foobarList_c
    foobar:
      c: foobar_c
      !!merge <<: *foo
      thing: foobar_thing

then

    yq '.foobar | [..]' sample.yml

will output

    - c: foobar_c
      !!merge <<: *foo
      thing: foobar_thing
    - foobar_c
    - *foo
    - foobar_thing

Reduce

Reduce is a powerful way to process a collection of data into a new form.

    <exp> as $<name> ireduce (<init>; <block>)

e.g.

    .[] as $item ireduce (0; . + $item)

On the LHS we are configuring the collection of items that will be reduced <exp> as well as what each element will be called $<name>. Note that the array has been splatted into its individual elements.

On the RHS there is <init>, the starting value of the accumulator and <block>, the expression that will update the accumulator for each element in the collection. Note that within the block expression, . will evaluate to the current value of the accumulator.

  yq vs jq syntax

Reduce syntax in yq is a little different from jq - as yq (currently) isn’t as sophisticated as jq and its only supports infix notation (e.g. a + b, where the operator is in the middle of the two parameters) - where as jq uses a mix of infix notation with prefix notation (e.g. reduce a b is like writing + a b).

To that end, the reduce operator is called ireduce for backwards compatibility if a jq like prefix version of reduce is ever added.

  Sum numbers

Given a sample.yml file of:

    - 10
    - 2
    - 5
    - 3

then

    yq '.[] as $item ireduce (0; . + $item)' sample.yml

will output

    20

  Merge all yaml files together

Given a sample.yml file of:

    a: cat

And another sample another.yml file of:

    b: dog

then

    yq eval-all '. as $item ireduce ({}; . * $item )' sample.yml another.yml

will output

    a: cat
    b: dog

  Convert an array to an object

Given a sample.yml file of:

    - name: Cathy
      has: apples
    - name: Bob
      has: bananas

then

    yq '.[] as $item ireduce ({}; .[$item | .name] = ($item | .has) )' sample.yml

will output

    Cathy: apples
    Bob: bananas

Reverse

Reverses the order of the items in an array

  Reverse

Given a sample.yml file of:

    - 1
    - 2
    - 3

then

    yq 'reverse' sample.yml

will output

    - 3
    - 2
    - 1

  Sort descending by string field

Use sort with reverse to sort in descending order.

Given a sample.yml file of:

    - a: banana
    - a: cat
    - a: apple

then

    yq 'sort_by(.a) | reverse' sample.yml

will output

    - a: cat
    - a: banana
    - a: apple

Select

Select is used to filter arrays and maps by a boolean expression.

  Related Operators

•   equals / not equals (==, !=) operators here (https://mikefarah.gitbook.io/yq/operators/equals)

•   comparison (>=, < etc) operators here (https://mikefarah.gitbook.io/yq/operators/compare)

•   boolean operators (and, or, any etc) here (https://mikefarah.gitbook.io/yq/operators/boolean-operators)

  Select elements from array using wildcard prefix

Given a sample.yml file of:

    - cat
    - goat
    - dog

then

    yq '.[] | select(. == "*at")' sample.yml

will output

    cat
    goat

  Select elements from array using wildcard suffix

Given a sample.yml file of:

    - go-kart
    - goat
    - dog

then

    yq '.[] | select(. == "go*")' sample.yml

will output

    go-kart
    goat

  Select elements from array using wildcard prefix and suffix

Given a sample.yml file of:

    - ago
    - go
    - meow
    - going

then

    yq '.[] | select(. == "*go*")' sample.yml

will output

    ago
    go
    going

  Select elements from array with regular expression

See more regular expression examples under the string operator docs (https://mikefarah.gitbook.io/yq/operators/string-operators).

Given a sample.yml file of:

    - this_0
    - not_this
    - nor_0_this
    - thisTo_4

then

    yq '.[] | select(test("[a-zA-Z]+_[0-9]$"))' sample.yml

will output

    this_0
    thisTo_4

  Select items from a map

Given a sample.yml file of:

    things: cat
    bob: goat
    horse: dog

then

    yq '.[] | select(. == "cat" or test("og$"))' sample.yml

will output

    cat
    dog

  Use select and with_entries to filter map keys

Given a sample.yml file of:

    name: bob
    legs: 2
    game: poker

then

    yq 'with_entries(select(.key | test("ame$")))' sample.yml

will output

    name: bob
    game: poker

  Select multiple items in a map and update

Note the brackets around the entire LHS.

Given a sample.yml file of:

    a:
      things: cat
      bob: goat
      horse: dog

then

    yq '(.a.[] | select(. == "cat" or . == "goat")) |= "rabbit"' sample.yml

will output

    a:
      things: rabbit
      bob: rabbit
      horse: dog

Shuffle

Shuffles an array. Note that this command does not use a cryptographically secure random number generator to randomise the array order.

  Shuffle array

Given a sample.yml file of:

    - 1
    - 2
    - 3
    - 4
    - 5

then

    yq 'shuffle' sample.yml

will output

    - 5
    - 2
    - 4
    - 1
    - 3

  Shuffle array in place

Given a sample.yml file of:

    cool:
      - 1
      - 2
      - 3
      - 4
      - 5

then

    yq '.cool |= shuffle' sample.yml

will output

    cool:
      - 5
      - 2
      - 4
      - 1
      - 3

Slice Array or String

The slice operator works on both arrays and strings. Like the jq equivalent, .[10:15] will return a subarray (or substring) of length 5, starting from index 10 inclusive, up to index 15 exclusive. Negative numbers count backwards from the end of the array or string.

You may leave out the first or second number, which will refer to the start or end of the array or string respectively.

  Slicing arrays

Given a sample.yml file of:

    - cat
    - dog
    - frog
    - cow

then

    yq '.[1:3]' sample.yml

will output

    - dog
    - frog

  Slicing arrays - without the first number

Starts from the start of the array

Given a sample.yml file of:

    - cat
    - dog
    - frog
    - cow

then

    yq '.[:2]' sample.yml

will output

    - cat
    - dog

  Slicing arrays - without the second number

Finishes at the end of the array

Given a sample.yml file of:

    - cat
    - dog
    - frog
    - cow

then

    yq '.[2:]' sample.yml

will output

    - frog
    - cow

  Slicing arrays - use negative numbers to count backwards from the end

Given a sample.yml file of:

    - cat
    - dog
    - frog
    - cow

then

    yq '.[1:-1]' sample.yml

will output

    - dog
    - frog

  Inserting into the middle of an array

using an expression to find the index

Given a sample.yml file of:

    - cat
    - dog
    - frog
    - cow

then

    yq '(.[] | select(. == "dog") | key + 1) as $pos | .[0:($pos)] + ["rabbit"] + .[$pos:]' sample.yml

will output

    - cat
    - dog
    - rabbit
    - frog
    - cow

  Slicing strings

Given a sample.yml file of:

    country: Australia

then

    yq '.country[0:5]' sample.yml

will output

    Austr

  Slicing strings - without the second number

Finishes at the end of the string

Given a sample.yml file of:

    country: Australia

then

    yq '.country[5:]' sample.yml

will output

    alia

  Slicing strings - without the first number

Starts from the start of the string

Given a sample.yml file of:

    country: Australia

then

    yq '.country[:5]' sample.yml

will output

    Austr

  Slicing strings - use negative numbers to count backwards from the end

Negative indices count from the end of the string

Given a sample.yml file of:

    country: Australia

then

    yq '.country[-5:]' sample.yml

will output

    ralia

  Slicing strings - Unicode

Indices are rune-based, so multi-byte characters are handled correctly

Given a sample.yml file of:

    greeting: héllo

then

    yq '.greeting[1:3]' sample.yml

will output

    él

Sort Keys

The Sort Keys operator sorts maps by their keys (based on their string value). This operator does not do anything to arrays or scalars (so you can easily recursively apply it to all maps).

Sort is particularly useful for diffing two different yaml documents:

    yq -i -P 'sort_keys(..)' file1.yml
    yq -i -P 'sort_keys(..)' file2.yml
    diff file1.yml file2.yml

Note that yq does not yet consider anchors when sorting by keys - this may result in invalid yaml documents if you are using merge anchors.

For more advanced sorting, you can use the sort_by (https://mikefarah.gitbook.io/yq/operators/sort) function on a map, and give it a custom function like sort_by(key | downcase).

  Sort keys of map

Given a sample.yml file of:

    c: frog
    a: blah
    b: bing

then

    yq 'sort_keys(.)' sample.yml

will output

    a: blah
    b: bing
    c: frog

  Sort keys recursively

Note the array elements are left unsorted, but maps inside arrays are sorted

Given a sample.yml file of:

    bParent:
      c: dog
      array:
        - 3
        - 1
        - 2
    aParent:
      z: donkey
      x:
        - c: yum
          b: delish
        - b: ew
          a: apple

then

    yq 'sort_keys(..)' sample.yml

will output

    aParent:
      x:
        - b: delish
          c: yum
        - a: apple
          b: ew
      z: donkey
    bParent:
      array:
        - 3
        - 1
        - 2
      c: dog

Sort

Sorts an array. Use sort to sort an array as is, or sort_by(exp) to sort by a particular expression (e.g. subfield).

To sort by descending order, pipe the results through the reverse operator after sorting.

Note that at this stage, yq only sorts scalar fields.

  Sort by string field

Given a sample.yml file of:

    - a: banana
    - a: cat
    - a: apple

then

    yq 'sort_by(.a)' sample.yml

will output

    - a: apple
    - a: banana
    - a: cat

  Sort by multiple fields

Given a sample.yml file of:

    - a: dog
    - a: cat
      b: banana
    - a: cat
      b: apple

then

    yq 'sort_by(.a, .b)' sample.yml

will output

    - a: cat
      b: apple
    - a: cat
      b: banana
    - a: dog

  Sort descending by string field

Use sort with reverse to sort in descending order.

Given a sample.yml file of:

    - a: banana
    - a: cat
    - a: apple

then

    yq 'sort_by(.a) | reverse' sample.yml

will output

    - a: cat
    - a: banana
    - a: apple

  Sort array in place

Given a sample.yml file of:

    cool:
      - a: banana
      - a: cat
      - a: apple

then

    yq '.cool |= sort_by(.a)' sample.yml

will output

    cool:
      - a: apple
      - a: banana
      - a: cat

  Sort array of objects by key

Note that you can give sort_by complex expressions, not just paths

Given a sample.yml file of:

    cool:
      - b: banana
      - a: banana
      - c: banana

then

    yq '.cool |= sort_by(keys | .[0])' sample.yml

will output

    cool:
      - a: banana
      - b: banana
      - c: banana

  Sort a map

Sorting a map, by default this will sort by the values

Given a sample.yml file of:

    y: b
    z: a
    x: c

then

    yq 'sort' sample.yml

will output

    z: a
    y: b
    x: c

  Sort a map by keys

Use sort_by to sort a map using a custom function

Given a sample.yml file of:

    Y: b
    z: a
    x: c

then

    yq 'sort_by(key | downcase)' sample.yml

will output

    x: c
    Y: b
    z: a

  Sort is stable

Note the order of the elements in unchanged when equal in sorting.

Given a sample.yml file of:

    - a: banana
      b: 1
    - a: banana
      b: 2
    - a: banana
      b: 3
    - a: banana
      b: 4

then

    yq 'sort_by(.a)' sample.yml

will output

    - a: banana
      b: 1
    - a: banana
      b: 2
    - a: banana
      b: 3
    - a: banana
      b: 4

  Sort by numeric field

Given a sample.yml file of:

    - a: 10
    - a: 100
    - a: 1

then

    yq 'sort_by(.a)' sample.yml

will output

    - a: 1
    - a: 10
    - a: 100

  Sort by custom date field

Given a sample.yml file of:

    - a: 12-Jun-2011
    - a: 23-Dec-2010
    - a: 10-Aug-2011

then

    yq 'with_dtf("02-Jan-2006"; sort_by(.a))' sample.yml

will output

    - a: 23-Dec-2010
    - a: 12-Jun-2011
    - a: 10-Aug-2011

  Sort, nulls come first

Given a sample.yml file of:

    - 8
    - 3
    - null
    - 6
    - true
    - false
    - cat

then

    yq 'sort' sample.yml

will output

    - null
    - false
    - true
    - 3
    - 6
    - 8
    - cat

Split into Documents

This operator splits all matches into separate documents

  Split empty

Running

    yq --null-input 'split_doc'

will output

  Split array

Given a sample.yml file of:

    - a: cat
    - b: dog

then

    yq '.[] | split_doc' sample.yml

will output

    a: cat
    ---
    b: dog

String Operators

  RegEx

This uses Golang’s native regex functions under the hood - See their docs (https://github.com/google/re2/wiki/Syntax) for the supported syntax.

Case insensitive tip: prefix the regex with (?i) - e.g. test("(?i)cats").

  match(regEx)

This operator returns the substring match details of the given regEx.

  capture(regEx)

Capture returns named RegEx capture groups in a map. Can be more convenient than match depending on what you are doing.

  test(regEx)

Returns true if the string matches the RegEx, false otherwise.

  sub(regEx, replacement)

Substitutes matched substrings. The first parameter is the regEx to match substrings within the original string. The second parameter specifies what to replace those matches with. This can refer to capture groups from the first RegEx.

  String blocks, bash and newlines

Bash is notorious for chomping on precious trailing newline characters, making it tricky to set strings with newlines properly. In particular, the $( exp ) will trim trailing newlines.

For instance to get this yaml:

    a: |
      cat

Using $( exp ) wont work, as it will trim the trailing newline.

    m=$(echo "cat\n") yq -n '.a = strenv(m)'
    a: cat

However, using printf works:

    printf -v m "cat\n" ; m="$m" yq -n '.a = strenv(m)'
    a: |
      cat

As well as having multiline expressions:

    m="cat
    "  yq -n '.a = strenv(m)'
    a: |
      cat

Similarly, if you’re trying to set the content from a file, and want a trailing newline:

    IFS= read -rd '' output < <(cat my_file)
    output=$output ./yq '.data.values = strenv(output)' first.yml

  Interpolation

Given a sample.yml file of:

    value: things
    another: stuff

then

    yq '.message = "I like \(.value) and \(.another)"' sample.yml

will output

    value: things
    another: stuff
    message: I like things and stuff

  Interpolation - not a string

Given a sample.yml file of:

    value:
      an: apple

then

    yq '.message = "I like \(.value)"' sample.yml

will output

    value:
      an: apple
    message: 'I like an: apple'

  To up (upper) case

Works with unicode characters

Given a sample.yml file of:

    água

then

    yq 'upcase' sample.yml

will output

    ÁGUA

  To down (lower) case

Works with unicode characters

Given a sample.yml file of:

    ÁgUA

then

    yq 'downcase' sample.yml

will output

    água

  Join strings

Given a sample.yml file of:

    - cat
    - meow
    - 1
    - null
    - true

then

    yq 'join("; ")' sample.yml

will output

    cat; meow; 1; ; true

  Trim strings

Given a sample.yml file of:

    - ' cat'
    - 'dog '
    - ' cow cow '
    - horse

then

    yq '.[] | trim' sample.yml

will output

    cat
    dog
    cow cow
    horse

  Match string

Given a sample.yml file of:

    foo bar foo

then

    yq 'match("foo")' sample.yml

will output

    string: foo
    offset: 0
    length: 3
    captures: []

  Match string, case insensitive

Given a sample.yml file of:

    foo bar FOO

then

    yq '[match("(?i)foo"; "g")]' sample.yml

will output

    - string: foo
      offset: 0
      length: 3
      captures: []
    - string: FOO
      offset: 8
      length: 3
      captures: []

  Match with global capture group

Given a sample.yml file of:

    abc abc

then

    yq '[match("(ab)(c)"; "g")]' sample.yml

will output

    - string: abc
      offset: 0
      length: 3
      captures:
        - string: ab
          offset: 0
          length: 2
        - string: c
          offset: 2
          length: 1
    - string: abc
      offset: 4
      length: 3
      captures:
        - string: ab
          offset: 4
          length: 2
        - string: c
          offset: 6
          length: 1

  Match with named capture groups

Given a sample.yml file of:

    foo bar foo foo  foo

then

    yq '[match("foo (?P<bar123>bar)? foo"; "g")]' sample.yml

will output

    - string: foo bar foo
      offset: 0
      length: 11
      captures:
        - string: bar
          offset: 4
          length: 3
          name: bar123
    - string: foo  foo
      offset: 12
      length: 8
      captures:
        - string: null
          offset: -1
          length: 0
          name: bar123

  Capture named groups into a map

Given a sample.yml file of:

    xyzzy-14

then

    yq 'capture("(?P<a>[a-z]+)-(?P<n>[0-9]+)")' sample.yml

will output

    a: xyzzy
    n: "14"

  Match without global flag

Given a sample.yml file of:

    cat cat

then

    yq 'match("cat")' sample.yml

will output

    string: cat
    offset: 0
    length: 3
    captures: []

  Match with global flag

Given a sample.yml file of:

    cat cat

then

    yq '[match("cat"; "g")]' sample.yml

will output

    - string: cat
      offset: 0
      length: 3
      captures: []
    - string: cat
      offset: 4
      length: 3
      captures: []

  Test using regex

Like jq’s equivalent, this works like match but only returns true/false instead of full match details

Given a sample.yml file of:

    - cat
    - dog

then

    yq '.[] | test("at")' sample.yml

will output

    true
    false

  Substitute / Replace string

This uses Golang’s regex, described here (https://github.com/google/re2/wiki/Syntax). Note the use of |= to run in context of the current string value.

Given a sample.yml file of:

    a: dogs are great

then

    yq '.a |= sub("dogs", "cats")' sample.yml

will output

    a: cats are great

  Substitute / Replace string with regex

This uses Golang’s regex, described here (https://github.com/google/re2/wiki/Syntax). Note the use of |= to run in context of the current string value.

Given a sample.yml file of:

    a: cat
    b: heat

then

    yq '.[] |= sub("(a)", "${1}r")' sample.yml

will output

    a: cart
    b: heart

  Custom types: that are really strings

When custom tags are encountered, yq will try to decode the underlying type.

Given a sample.yml file of:

    a: !horse cat
    b: !goat heat

then

    yq '.[] |= sub("(a)", "${1}r")' sample.yml

will output

    a: !horse cart
    b: !goat heart

  Split strings

Given a sample.yml file of:

    cat; meow; 1; ; true

then

    yq 'split("; ")' sample.yml

will output

    - cat
    - meow
    - "1"
    - ""
    - "true"

  Split strings one match

Given a sample.yml file of:

    word

then

    yq 'split("; ")' sample.yml

will output

    - word

  To string

Note that you may want to force yq to leave scalar values wrapped by passing in --unwrapScalar=false or -r=f

Given a sample.yml file of:

    - 1
    - true
    - null
    - ~
    - cat
    - an: object
    - - array
      - 2

then

    yq '.[] |= to_string' sample.yml

will output

    - "1"
    - "true"
    - "null"
    - "~"
    - cat
    - "an: object"
    - "- array\n- 2"

Style

The style operator can be used to get or set the style of nodes (e.g. string style, yaml style). Use this to control the formatting of the document in yaml.

  Update and set style of a particular node (simple)

Given a sample.yml file of:

    a:
      b: thing
      c: something

then

    yq '.a.b = "new" | .a.b style="double"' sample.yml

will output

    a:
      b: "new"
      c: something

  Update and set style of a particular node using path variables

Given a sample.yml file of:

    a:
      b: thing
      c: something

then

    yq 'with(.a.b ; . = "new" | . style="double")' sample.yml

will output

    a:
      b: "new"
      c: something

  Set tagged style

Given a sample.yml file of:

    a: cat
    b: 5
    c: 3.2
    e: true
    f:
      - 1
      - 2
      - 3
    g:
      something: cool

then

    yq '.. style="tagged"' sample.yml

will output

    !!map
    a: !!str cat
    b: !!int 5
    c: !!float 3.2
    e: !!bool true
    f: !!seq
      - !!int 1
      - !!int 2
      - !!int 3
    g: !!map
      something: !!str cool

  Set double quote style

Given a sample.yml file of:

    a: cat
    b: 5
    c: 3.2
    e: true
    f:
      - 1
      - 2
      - 3
    g:
      something: cool

then

    yq '.. style="double"' sample.yml

will output

    a: "cat"
    b: "5"
    c: "3.2"
    e: "true"
    f:
      - "1"
      - "2"
      - "3"
    g:
      something: "cool"

  Set double quote style on map keys too

Given a sample.yml file of:

    a: cat
    b: 5
    c: 3.2
    e: true
    f:
      - 1
      - 2
      - 3
    g:
      something: cool

then

    yq '... style="double"' sample.yml

will output

    "a": "cat"
    "b": "5"
    "c": "3.2"
    "e": "true"
    "f":
      - "1"
      - "2"
      - "3"
    "g":
      "something": "cool"

  Set single quote style

Given a sample.yml file of:

    a: cat
    b: 5
    c: 3.2
    e: true
    f:
      - 1
      - 2
      - 3
    g:
      something: cool

then

    yq '.. style="single"' sample.yml

will output

    a: 'cat'
    b: '5'
    c: '3.2'
    e: 'true'
    f:
      - '1'
      - '2'
      - '3'
    g:
      something: 'cool'

  Set literal quote style

Given a sample.yml file of:

    a: cat
    b: 5
    c: 3.2
    e: true
    f:
      - 1
      - 2
      - 3
    g:
      something: cool

then

    yq '.. style="literal"' sample.yml

will output

    a: |-
      cat
    b: |-
      5
    c: |-
      3.2
    e: |-
      true
    f:
      - |-
        1
      - |-
        2
      - |-
        3
    g:
      something: |-
        cool

  Set folded quote style

Given a sample.yml file of:

    a: cat
    b: 5
    c: 3.2
    e: true
    f:
      - 1
      - 2
      - 3
    g:
      something: cool

then

    yq '.. style="folded"' sample.yml

will output

    a: >-
      cat
    b: >-
      5
    c: >-
      3.2
    e: >-
      true
    f:
      - >-
        1
      - >-
        2
      - >-
        3
    g:
      something: >-
        cool

  Set flow quote style

Given a sample.yml file of:

    a: cat
    b: 5
    c: 3.2
    e: true
    f:
      - 1
      - 2
      - 3
    g:
      something: cool

then

    yq '.. style="flow"' sample.yml

will output

    {a: cat, b: 5, c: 3.2, e: true, f: [1, 2, 3], g: {something: cool}}

  Reset style - or pretty print

Set empty (default) quote style, note the usage of ... to match keys too. Note that there is a --prettyPrint/-P short flag for this.

Given a sample.yml file of:

    {a: cat, "b": 5, 'c': 3.2, "e": true,  f: [1,2,3], "g": { something: "cool"} }

then

    yq '... style=""' sample.yml

will output

    a: cat
    b: 5
    c: 3.2
    e: true
    f:
      - 1
      - 2
      - 3
    g:
      something: cool

  Set style relatively with assign-update

Given a sample.yml file of:

    a: single
    b: double

then

    yq '.[] style |= .' sample.yml

will output

    a: 'single'
    b: "double"

  Read style

Given a sample.yml file of:

    {a: "cat", b: 'thing'}

then

    yq '.. | style' sample.yml

will output

    flow
    double
    single

Subtract

You can use subtract to subtract numbers as well as remove elements from an array.

  Array subtraction

Running

    yq --null-input '[1,2] - [2,3]'

will output

    - 1

  Array subtraction with nested array

Running

    yq --null-input '[[1], 1, 2] - [[1], 3]'

will output

    - 1
    - 2

  Array subtraction with nested object

Note that order of the keys does not matter

Given a sample.yml file of:

    - a: b
      c: d
    - a: b

then

    yq '. - [{"c": "d", "a": "b"}]' sample.yml

will output

    - a: b

  Number subtraction - float

If the lhs or rhs are floats then the expression will be calculated with floats.

Given a sample.yml file of:

    a: 3
    b: 4.5

then

    yq '.a = .a - .b' sample.yml

will output

    a: -1.5
    b: 4.5

  Number subtraction - int

If both the lhs and rhs are ints then the expression will be calculated with ints.

Given a sample.yml file of:

    a: 3
    b: 4

then

    yq '.a = .a - .b' sample.yml

will output

    a: -1
    b: 4

  Decrement numbers

Given a sample.yml file of:

    a: 3
    b: 5

then

    yq '.[] -= 1' sample.yml

will output

    a: 2
    b: 4

  Date subtraction

You can subtract durations from dates. Assumes RFC3339 date time format, see date-time operators (https://mikefarah.gitbook.io/yq/operators/date-time-operators) for more information.

Given a sample.yml file of:

    a: 2021-01-01T03:10:00Z

then

    yq '.a -= "3h10m"' sample.yml

will output

    a: 2021-01-01T00:00:00Z

  Date subtraction - custom format

Use with_dtf to specify your datetime format. See date-time operators (https://mikefarah.gitbook.io/yq/operators/date-time-operators) for more information.

Given a sample.yml file of:

    a: Saturday, 15-Dec-01 at 6:00AM GMT

then

    yq 'with_dtf("Monday, 02-Jan-06 at 3:04PM MST", .a -= "3h1m")' sample.yml

will output

    a: Saturday, 15-Dec-01 at 2:59AM GMT

  Custom types: that are really numbers

When custom tags are encountered, yq will try to decode the underlying type.

Given a sample.yml file of:

    a: !horse 2
    b: !goat 1

then

    yq '.a -= .b' sample.yml

will output

    a: !horse 1
    b: !goat 1

System Operators

The system operator allows you to run an external command and use its output as a value in your expression.

Security warning: The system operator is disabled by default. You must explicitly pass --security-enable-system-operator to use it.

Note: When enabled, the system operator can replicate the functionality of env and load operators via external commands. Enabling it effectively overrides --security-disable-env-ops and --security-disable-file-ops.

  Usage

    yq --security-enable-system-operator --null-input '.field = system("command"; "arg1")'

The operator takes: - A command string (required) - An argument (or an array of arguments), separated from the command by ; (optional)

The current matched node’s value is serialised and piped to the command via stdin. The command’s stdout (with trailing newline stripped) is returned as a string.

  Disabling the system operator

The system operator is disabled by default. When disabled, an error is returned instead of running the command, consistent with --security-disable-env-ops and --security-disable-file-ops.

Use --security-enable-system-operator flag to enable it.

  system operator returns error when disabled

Use --security-enable-system-operator to enable the system operator.

Given a sample.yml file of:

    country: Australia

then

    yq '.country = system("/usr/bin/echo"; "test")' sample.yml

will output

    Error: system operations are disabled, use --security-enable-system-operator to enable

  Run a command with an argument

Use --security-enable-system-operator to enable the system operator.

Given a sample.yml file of:

    country: Australia

then

    yq --security-enable-system-operator '.country = system("/bin/echo"; "test")' sample.yml

will output

    country: test

  Run a command without arguments

Omit the semicolon and args to run the command with no extra arguments.

Given a sample.yml file of:

    a: hello

then

    yq --security-enable-system-operator '.a = system("/bin/echo")' sample.yml

will output

    a: ""

Tag

The tag operator can be used to get or set the tag of nodes (e.g. !!str, !!int, !!bool).

  Get tag

Given a sample.yml file of:

    a: cat
    b: 5
    c: 3.2
    e: true
    f: []

then

    yq '.. | tag' sample.yml

will output

    !!map
    !!str
    !!int
    !!float
    !!bool
    !!seq

  type is an alias for tag

Given a sample.yml file of:

    a: cat
    b: 5
    c: 3.2
    e: true
    f: []

then

    yq '.. | type' sample.yml

will output

    !!map
    !!str
    !!int
    !!float
    !!bool
    !!seq

  Set custom tag

Given a sample.yml file of:

    a: str

then

    yq '.a tag = "!!mikefarah"' sample.yml

will output

    a: !!mikefarah str

  Find numbers and convert them to strings

Given a sample.yml file of:

    a: cat
    b: 5
    c: 3.2
    e: true

then

    yq '(.. | select(tag == "!!int")) tag= "!!str"' sample.yml

will output

    a: cat
    b: "5"
    c: 3.2
    e: true

To Number

Parses the input as a number. yq will try to parse values as an int first, failing that it will try float. Values that already ints or floats will be left alone.

  Converts strings to numbers

Given a sample.yml file of:

    - "3"
    - "3.1"
    - "-1e3"

then

    yq '.[] | to_number' sample.yml

will output

    3
    3.1
    -1e3

  Doesn’t change numbers

Given a sample.yml file of:

    - 3
    - 3.1
    - -1e3

then

    yq '.[] | to_number' sample.yml

will output

    3
    3.1
    -1e3

  Cannot convert null

Running

    yq --null-input '.a.b | to_number'

will output

    Error: cannot convert node value [null] at path a.b of tag !!null to number

Traverse (Read)

This is the simplest (and perhaps most used) operator. It is used to navigate deeply into yaml structures.

  NOTE –yaml-fix-merge-anchor-to-spec flag

yq doesn’t merge anchors <<: to spec, in some circumstances it incorrectly overrides existing keys when the spec documents not to do that.

To minimise disruption while still fixing the issue, a flag has been added to toggle this behaviour. This will first default to false; and log warnings to users. Then it will default to true (and still allow users to specify false if needed)

See examples of the flag differences below, where LEGACY is the flag off; and FIXED is with the flag on.

  Simple map navigation

Given a sample.yml file of:

    a:
      b: apple

then

    yq '.a' sample.yml

will output

    b: apple

  Splat

Often used to pipe children into other operators

Given a sample.yml file of:

    - b: apple
    - c: banana

then

    yq '.[]' sample.yml

will output

    b: apple
    c: banana

  Optional Splat

Just like splat, but won’t error if you run it against scalars

Given a sample.yml file of:

    cat

then

    yq '.[]' sample.yml

will output

  Special characters

Use quotes with square brackets around path elements with special characters

Given a sample.yml file of:

    "{}": frog

then

    yq '.["{}"]' sample.yml

will output

    frog

  Nested special characters

Given a sample.yml file of:

    a:
      "key.withdots":
        "another.key": apple

then

    yq '.a["key.withdots"]["another.key"]' sample.yml

will output

    apple

  Keys with spaces

Use quotes with square brackets around path elements with special characters

Given a sample.yml file of:

    "red rabbit": frog

then

    yq '.["red rabbit"]' sample.yml

will output

    frog

  Dynamic keys

Expressions within [] can be used to dynamically lookup / calculate keys

Given a sample.yml file of:

    b: apple
    apple: crispy yum
    banana: soft yum

then

    yq '.[.b]' sample.yml

will output

    crispy yum

  Children don’t exist

Nodes are added dynamically while traversing

Given a sample.yml file of:

    c: banana

then

    yq '.a.b' sample.yml

will output

    null

  Optional identifier

Like jq, does not output an error when the yaml is not an array or object as expected

Given a sample.yml file of:

    - 1
    - 2
    - 3

then

    yq '.a?' sample.yml

will output

  Wildcard matching

Given a sample.yml file of:

    a:
      cat: apple
      mad: things

then

    yq '.a."*a*"' sample.yml

will output

    apple
    things

  Aliases

Given a sample.yml file of:

    a: &cat
      c: frog
    b: *cat

then

    yq '.b' sample.yml

will output

    *cat

  Traversing aliases with splat

Given a sample.yml file of:

    a: &cat
      c: frog
    b: *cat

then

    yq '.b[]' sample.yml

will output

    frog

  Traversing aliases explicitly

Given a sample.yml file of:

    a: &cat
      c: frog
    b: *cat

then

    yq '.b.c' sample.yml

will output

    frog

  Traversing arrays by index

Given a sample.yml file of:

    - 1
    - 2
    - 3

then

    yq '.[0]' sample.yml

will output

    1

  Traversing nested arrays by index

Given a sample.yml file of:

    [[], [cat]]

then

    yq '.[1][0]' sample.yml

will output

    cat

  Maps with numeric keys

Given a sample.yml file of:

    2: cat

then

    yq '.[2]' sample.yml

will output

    cat

  Maps with non existing numeric keys

Given a sample.yml file of:

    a: b

then

    yq '.[0]' sample.yml

will output

    null

  Traversing merge anchors

Given a sample.yml file of:

    foo: &foo
      a: foo_a
      thing: foo_thing
      c: foo_c
    bar: &bar
      b: bar_b
      thing: bar_thing
      c: bar_c
    foobarList:
      b: foobarList_b
      !!merge <<:
        - *foo
        - *bar
      c: foobarList_c
    foobar:
      c: foobar_c
      !!merge <<: *foo
      thing: foobar_thing

then

    yq '.foobar.a' sample.yml

will output

    foo_a

  Traversing merge anchors with local override

Given a sample.yml file of:

    foo: &foo
      a: foo_a
      thing: foo_thing
      c: foo_c
    bar: &bar
      b: bar_b
      thing: bar_thing
      c: bar_c
    foobarList:
      b: foobarList_b
      !!merge <<:
        - *foo
        - *bar
      c: foobarList_c
    foobar:
      c: foobar_c
      !!merge <<: *foo
      thing: foobar_thing

then

    yq '.foobar.thing' sample.yml

will output

    foobar_thing

  Select multiple indices

Given a sample.yml file of:

    a:
      - a
      - b
      - c

then

    yq '.a[0, 2]' sample.yml

will output

    a
    c

  LEGACY: Traversing merge anchors with override

This is legacy behaviour, see –yaml-fix-merge-anchor-to-spec

Given a sample.yml file of:

    foo: &foo
      a: foo_a
      thing: foo_thing
      c: foo_c
    bar: &bar
      b: bar_b
      thing: bar_thing
      c: bar_c
    foobarList:
      b: foobarList_b
      !!merge <<:
        - *foo
        - *bar
      c: foobarList_c
    foobar:
      c: foobar_c
      !!merge <<: *foo
      thing: foobar_thing

then

    yq '.foobar.c' sample.yml

will output

    foo_c

  LEGACY: Traversing merge anchor lists

Note that the later merge anchors override previous, but this is legacy behaviour, see –yaml-fix-merge-anchor-to-spec

Given a sample.yml file of:

    foo: &foo
      a: foo_a
      thing: foo_thing
      c: foo_c
    bar: &bar
      b: bar_b
      thing: bar_thing
      c: bar_c
    foobarList:
      b: foobarList_b
      !!merge <<:
        - *foo
        - *bar
      c: foobarList_c
    foobar:
      c: foobar_c
      !!merge <<: *foo
      thing: foobar_thing

then

    yq '.foobarList.thing' sample.yml

will output

    bar_thing

  LEGACY: Splatting merge anchors

With legacy override behaviour, see –yaml-fix-merge-anchor-to-spec

Given a sample.yml file of:

    foo: &foo
      a: foo_a
      thing: foo_thing
      c: foo_c
    bar: &bar
      b: bar_b
      thing: bar_thing
      c: bar_c
    foobarList:
      b: foobarList_b
      !!merge <<:
        - *foo
        - *bar
      c: foobarList_c
    foobar:
      c: foobar_c
      !!merge <<: *foo
      thing: foobar_thing

then

    yq '.foobar[]' sample.yml

will output

    foo_c
    foo_a
    foobar_thing

  LEGACY: Splatting merge anchor lists

With legacy override behaviour, see –yaml-fix-merge-anchor-to-spec

Given a sample.yml file of:

    foo: &foo
      a: foo_a
      thing: foo_thing
      c: foo_c
    bar: &bar
      b: bar_b
      thing: bar_thing
      c: bar_c
    foobarList:
      b: foobarList_b
      !!merge <<:
        - *foo
        - *bar
      c: foobarList_c
    foobar:
      c: foobar_c
      !!merge <<: *foo
      thing: foobar_thing

then

    yq '.foobarList[]' sample.yml

will output

    bar_b
    foo_a
    bar_thing
    foobarList_c

  FIXED: Traversing merge anchors with override

Set --yaml-fix-merge-anchor-to-spec=true to get this correct merge behaviour.

Given a sample.yml file of:

    foo: &foo
      a: foo_a
      thing: foo_thing
      c: foo_c
    bar: &bar
      b: bar_b
      thing: bar_thing
      c: bar_c
    foobarList:
      b: foobarList_b
      !!merge <<:
        - *foo
        - *bar
      c: foobarList_c
    foobar:
      c: foobar_c
      !!merge <<: *foo
      thing: foobar_thing

then

    yq '.foobar.c' sample.yml

will output

    foobar_c

  FIXED: Traversing merge anchor lists

Set --yaml-fix-merge-anchor-to-spec=true to get this correct merge behaviour. Note that the keys earlier in the merge anchors sequence override later ones

Given a sample.yml file of:

    foo: &foo
      a: foo_a
      thing: foo_thing
      c: foo_c
    bar: &bar
      b: bar_b
      thing: bar_thing
      c: bar_c
    foobarList:
      b: foobarList_b
      !!merge <<:
        - *foo
        - *bar
      c: foobarList_c
    foobar:
      c: foobar_c
      !!merge <<: *foo
      thing: foobar_thing

then

    yq '.foobarList.thing' sample.yml

will output

    foo_thing

  FIXED: Splatting merge anchors

Set --yaml-fix-merge-anchor-to-spec=true to get this correct merge behaviour. Note that the keys earlier in the merge anchors sequence override later ones

Given a sample.yml file of:

    foo: &foo
      a: foo_a
      thing: foo_thing
      c: foo_c
    bar: &bar
      b: bar_b
      thing: bar_thing
      c: bar_c
    foobarList:
      b: foobarList_b
      !!merge <<:
        - *foo
        - *bar
      c: foobarList_c
    foobar:
      c: foobar_c
      !!merge <<: *foo
      thing: foobar_thing

then

    yq '.foobar[]' sample.yml

will output

    foo_a
    foobar_thing
    foobar_c

  FIXED: Splatting merge anchor lists

Set --yaml-fix-merge-anchor-to-spec=true to get this correct merge behaviour. Note that the keys earlier in the merge anchors sequence override later ones

Given a sample.yml file of:

    foo: &foo
      a: foo_a
      thing: foo_thing
      c: foo_c
    bar: &bar
      b: bar_b
      thing: bar_thing
      c: bar_c
    foobarList:
      b: foobarList_b
      !!merge <<:
        - *foo
        - *bar
      c: foobarList_c
    foobar:
      c: foobar_c
      !!merge <<: *foo
      thing: foobar_thing

then

    yq '.foobarList[]' sample.yml

will output

    foobarList_b
    foo_thing
    foobarList_c
    foo_a

Union

This operator is used to combine different results together.

  Combine scalars

Running

    yq --null-input '1, true, "cat"'

will output

    1
    true
    cat

  Combine selected paths

Given a sample.yml file of:

    a: fieldA
    b: fieldB
    c: fieldC

then

    yq '.a, .c' sample.yml

will output

    fieldA
    fieldC

Unique

This is used to filter out duplicated items in an array. Note that the original order of the array is maintained.

  Unique array of scalars (string/numbers)

Note that unique maintains the original order of the array.

Given a sample.yml file of:

    - 2
    - 1
    - 3
    - 2

then

    yq 'unique' sample.yml

will output

    - 2
    - 1
    - 3

  Unique nulls

Unique works on the node value, so it considers different representations of nulls to be different

Given a sample.yml file of:

    - ~
    - null
    - ~
    - null

then

    yq 'unique' sample.yml

will output

    - ~
    - null

  Unique all nulls

Run against the node tag to unique all the nulls

Given a sample.yml file of:

    - ~
    - null
    - ~
    - null

then

    yq 'unique_by(tag)' sample.yml

will output

    - ~

  Unique array objects

Given a sample.yml file of:

    - name: harry
      pet: cat
    - name: billy
      pet: dog
    - name: harry
      pet: cat

then

    yq 'unique' sample.yml

will output

    - name: harry
      pet: cat
    - name: billy
      pet: dog

  Unique array of objects by a field

Given a sample.yml file of:

    - name: harry
      pet: cat
    - name: billy
      pet: dog
    - name: harry
      pet: dog

then

    yq 'unique_by(.name)' sample.yml

will output

    - name: harry
      pet: cat
    - name: billy
      pet: dog

  Unique array of arrays

Given a sample.yml file of:

    - - cat
      - dog
    - - cat
      - sheep
    - - cat
      - dog

then

    yq 'unique' sample.yml

will output

    - - cat
      - dog
    - - cat
      - sheep

Variable Operators

Like the jq equivalents, variables are sometimes required for the more complex expressions (or swapping values between fields).

Note that there is also an additional ref operator that holds a reference (instead of a copy) of the path, allowing you to make multiple changes to the same path.

  Single value variable

Given a sample.yml file of:

    a: cat

then

    yq '.a as $foo | $foo' sample.yml

will output

    cat

  Multi value variable

Given a sample.yml file of:

    - cat
    - dog

then

    yq '.[] as $foo | $foo' sample.yml

will output

    cat
    dog

  Using variables as a lookup

Example taken from jq (https://stedolan.github.io/jq/manual/#Variable/SymbolicBindingOperator:...as$identifier%7C...)

Given a sample.yml file of:

    "posts":
      - "title": First post
        "author": anon
      - "title": A well-written article
        "author": person1
    "realnames":
      "anon": Anonymous Coward
      "person1": Person McPherson

then

    yq '.realnames as $names | .posts[] | {"title":.title, "author": $names[.author]}' sample.yml

will output

    title: First post
    author: Anonymous Coward
    title: A well-written article
    author: Person McPherson

  Using variables to swap values

Given a sample.yml file of:

    a: a_value
    b: b_value

then

    yq '.a as $x  | .b as $y | .b = $x | .a = $y' sample.yml

will output

    a: b_value
    b: a_value

  Use ref to reference a path repeatedly

Note: You may find the with operator more useful.

Given a sample.yml file of:

    a:
      b: thing
      c: something

then

    yq '.a.b ref $x | $x = "new" | $x style="double"' sample.yml

will output

    a:
      b: "new"
      c: something

With

Use the with operator to conveniently make multiple updates to a deeply nested path, or to update array elements relatively to each other. The first argument expression sets the root context, and the second expression runs against that root context.

  Update and style

Given a sample.yml file of:

    a:
      deeply:
        nested: value

then

    yq 'with(.a.deeply.nested; . = "newValue" | . style="single")' sample.yml

will output

    a:
      deeply:
        nested: 'newValue'

  Update multiple deeply nested properties

Given a sample.yml file of:

    a:
      deeply:
        nested: value
        other: thing

then

    yq 'with(.a.deeply; .nested = "newValue" | .other= "newThing")' sample.yml

will output

    a:
      deeply:
        nested: newValue
        other: newThing

  Update array elements relatively

The second expression runs with each element of the array as it’s contextual root. This allows you to make updates relative to the element.

Given a sample.yml file of:

    myArray:
      - a: apple
      - a: banana

then

    yq 'with(.myArray[]; .b = .a + " yum")' sample.yml

will output

    myArray:
      - a: apple
        b: apple yum
      - a: banana
        b: banana yum

Base64

Encode and decode to and from Base64.

Base64 assumes RFC4648 (https://rfc-editor.org/rfc/rfc4648.html) encoding. Encoding and decoding both assume that the content is a UTF-8 string and not binary content.

See below for examples

  Decode base64: simple

Decoded data is assumed to be a string.

Given a sample.txt file of:

    YSBzcGVjaWFsIHN0cmluZw==

then

    yq -p=base64 -oy '.' sample.txt

will output

    a special string

  Decode base64: UTF-8

Base64 decoding supports UTF-8 encoded strings.

Given a sample.txt file of:

    V29ya3Mgd2l0aCBVVEYtMTYg8J+Yig==

then

    yq -p=base64 -oy '.' sample.txt

will output

    Works with UTF-16 😊

  Decode with extra spaces

Extra leading/trailing whitespace is stripped

Given a sample.txt file of:

     YSBzcGVjaWFsIHN0cmluZw==

then

    yq -p=base64 -oy '.' sample.txt

will output

    a special string

  Encode base64: string

Given a sample.yml file of:

    "a special string"

then

    yq -o=base64 '.' sample.yml

will output

    YSBzcGVjaWFsIHN0cmluZw==```
    ## Encode base64: string from document
    Extract a string field and encode it to base64.
    Given a sample.yml file of:
    ```yaml
    coolData: "a special string"

then

    yq -o=base64 '.coolData' sample.yml

will output

    YSBzcGVjaWFsIHN0cmluZw==```
    # JSON
    Encode and decode to and from JSON. Supports multiple JSON documents in a single file (e.g. NDJSON).
    Note that YAML is a superset of (single document) JSON - so you don't have to use the JSON parser to read JSON when there is only one JSON document in the input. You will probably want to pretty print the result in this case, to get idiomatic YAML styling.
    ## Parse json: simple
    JSON is a subset of yaml, so all you need to do is prettify the output
    Given a sample.json file of:
    ```json
    {"cat": "meow"}

then

    yq -p=json sample.json

will output

    cat: meow

  Parse json: complex

JSON is a subset of yaml, so all you need to do is prettify the output

Given a sample.json file of:

    {"a":"Easy! as one two three","b":{"c":2,"d":[3,4]}}

then

    yq -p=json sample.json

will output

    a: Easy! as one two three
    b:
      c: 2
      d:
        - 3
        - 4

  Encode json: simple

Given a sample.yml file of:

    cat: meow

then

    yq -o=json '.' sample.yml

will output

    {
      "cat": "meow"
    }

  Encode json: simple - in one line

Given a sample.yml file of:

    cat: meow # this is a comment, and it will be dropped.

then

    yq -o=json -I=0 '.' sample.yml

will output

    {"cat":"meow"}

  Encode json: comments

Given a sample.yml file of:

    cat: meow # this is a comment, and it will be dropped.

then

    yq -o=json '.' sample.yml

will output

    {
      "cat": "meow"
    }

  Encode json: anchors

Anchors are dereferenced

Given a sample.yml file of:

    cat: &ref meow
    anotherCat: *ref

then

    yq -o=json '.' sample.yml

will output

    {
      "cat": "meow",
      "anotherCat": "meow"
    }

  Encode json: multiple results

Each matching node is converted into a json doc. This is best used with 0 indent (json document per line)

Given a sample.yml file of:

    things: [{stuff: cool}, {whatever: cat}]

then

    yq -o=json -I=0 '.things[]' sample.yml

will output

    {"stuff":"cool"}
    {"whatever":"cat"}

  Encode json: preserve floats with trailing zero

Whole-number floats keep their decimal point so downstream consumers see a JSON number with a fractional part (matches Go’s encoding/json, Python’s json, and jq).

Given a sample.yml file of:

    percentiles: [50.0, 95.0, 99.0, 99.9]

then

    yq -o=json -I=0 '.' sample.yml

will output

    {"percentiles":[50.0,95.0,99.0,99.9]}

  Roundtrip JSON Lines / NDJSON

Given a sample.json file of:

    {"this": "is a multidoc json file"}
    {"each": ["line is a valid json document"]}
    {"a number": 4}

then

    yq -p=json -o=json -I=0 sample.json

will output

    {"this":"is a multidoc json file"}
    {"each":["line is a valid json document"]}
    {"a number":4}

  Roundtrip multi-document JSON

The parser can also handle multiple multi-line json documents in a single file (despite this not being in the JSON Lines / NDJSON spec). Typically you would have one entire JSON document per line, but the parser also supports multiple multi-line json documents

Given a sample.json file of:

    {
        "this": "is a multidoc json file"
    }
    {
        "it": [
            "has",
            "consecutive",
            "json documents"
        ]
    }
    {
        "a number": 4
    }

then

    yq -p=json -o=json -I=2 sample.json

will output

    {
      "this": "is a multidoc json file"
    }
    {
      "it": [
        "has",
        "consecutive",
        "json documents"
      ]
    }
    {
      "a number": 4
    }

  Update a specific document in a multi-document json

Documents are indexed by the documentIndex or di operator.

Given a sample.json file of:

    {"this": "is a multidoc json file"}
    {"each": ["line is a valid json document"]}
    {"a number": 4}

then

    yq -p=json -o=json -I=0 '(select(di == 1) | .each ) += "cool"' sample.json

will output

    {"this":"is a multidoc json file"}
    {"each":["line is a valid json document","cool"]}
    {"a number":4}

  Find and update a specific document in a multi-document json

Use expressions as you normally would.

Given a sample.json file of:

    {"this": "is a multidoc json file"}
    {"each": ["line is a valid json document"]}
    {"a number": 4}

then

    yq -p=json -o=json -I=0 '(select(has("each")) | .each ) += "cool"' sample.json

will output

    {"this":"is a multidoc json file"}
    {"each":["line is a valid json document","cool"]}
    {"a number":4}

  Decode JSON Lines / NDJSON

Given a sample.json file of:

    {"this": "is a multidoc json file"}
    {"each": ["line is a valid json document"]}
    {"a number": 4}

then

    yq -p=json sample.json

will output

    this: is a multidoc json file
    ---
    each:
      - line is a valid json document
    ---
    a number: 4

CSV

Encode/Decode/Roundtrip CSV and TSV files.

  Encode

Currently supports arrays of homogeneous flat objects, that is: no nesting and it assumes the first object has all the keys required:

    - name: Bobo
      type: dog
    - name: Fifi
      type: cat

As well as arrays of arrays of scalars (strings/numbers/booleans):

    - [Bobo, dog]
    - [Fifi, cat]

  Decode

Decode assumes the first CSV/TSV row is the header row, and all rows beneath are the entries. The data will be coded into an array of objects, using the header rows as keys.

    name,type
    Bobo,dog
    Fifi,cat

  Encode CSV simple

Given a sample.yml file of:

    - [i, like, csv]
    - [because, excel, is, cool]

then

    yq -o=csv sample.yml

will output

    i,like,csv
    because,excel,is,cool

  Encode TSV simple

Given a sample.yml file of:

    - [i, like, csv]
    - [because, excel, is, cool]

then

    yq -o=tsv sample.yml

will output

    i   like    csv
    because excel   is  cool

  Encode array of objects to csv

Given a sample.yml file of:

    - name: Gary
      numberOfCats: 1
      likesApples: true
      height: 168.8
    - name: Samantha's Rabbit
      numberOfCats: 2
      likesApples: false
      height: -188.8

then

    yq -o=csv sample.yml

will output

    name,numberOfCats,likesApples,height
    Gary,1,true,168.8
    Samantha's Rabbit,2,false,-188.8

  Encode array of objects to custom csv format

Add the header row manually, then the we convert each object into an array of values - resulting in an array of arrays. Pick the columns and call the header whatever you like.

Given a sample.yml file of:

    - name: Gary
      numberOfCats: 1
      likesApples: true
      height: 168.8
    - name: Samantha's Rabbit
      numberOfCats: 2
      likesApples: false
      height: -188.8

then

    yq -o=csv '[["Name", "Number of Cats"]] +  [.[] | [.name, .numberOfCats ]]' sample.yml

will output

    Name,Number of Cats
    Gary,1
    Samantha's Rabbit,2

  Encode array of objects to csv - missing fields behaviour

First entry is used to determine the headers, and it is missing `likesApples', so it is not included in the csv. Second entry does not have `numberOfCats' so that is blank

Given a sample.yml file of:

    - name: Gary
      numberOfCats: 1
      height: 168.8
    - name: Samantha's Rabbit
      height: -188.8
      likesApples: false

then

    yq -o=csv sample.yml

will output

    name,numberOfCats,height
    Gary,1,168.8
    Samantha's Rabbit,,-188.8

  Parse CSV into an array of objects

First row is assumed to be the header row. By default, entries with YAML/JSON formatting will be parsed!

Given a sample.csv file of:

    name,numberOfCats,likesApples,height,facts
    Gary,1,true,168.8,cool: true
    Samantha's Rabbit,2,false,-188.8,tall: indeed

then

    yq -p=csv sample.csv

will output

    - name: Gary
      numberOfCats: 1
      likesApples: true
      height: 168.8
      facts:
        cool: true
    - name: Samantha's Rabbit
      numberOfCats: 2
      likesApples: false
      height: -188.8
      facts:
        tall: indeed

  Parse CSV into an array of objects, no auto-parsing

First row is assumed to be the header row. Entries with YAML/JSON will be left as strings.

Given a sample.csv file of:

    name,numberOfCats,likesApples,height,facts
    Gary,1,true,168.8,cool: true
    Samantha's Rabbit,2,false,-188.8,tall: indeed

then

    yq -p=csv --csv-auto-parse=f sample.csv

will output

    - name: Gary
      numberOfCats: 1
      likesApples: true
      height: 168.8
      facts: 'cool: true'
    - name: Samantha's Rabbit
      numberOfCats: 2
      likesApples: false
      height: -188.8
      facts: 'tall: indeed'

  Parse TSV into an array of objects

First row is assumed to be the header row.

Given a sample.tsv file of:

    name    numberOfCats    likesApples height
    Gary    1   true    168.8
    Samantha's Rabbit   2   false   -188.8

then

    yq -p=tsv sample.tsv

will output

    - name: Gary
      numberOfCats: 1
      likesApples: true
      height: 168.8
    - name: Samantha's Rabbit
      numberOfCats: 2
      likesApples: false
      height: -188.8

  Round trip

Given a sample.csv file of:

    name,numberOfCats,likesApples,height
    Gary,1,true,168.8
    Samantha's Rabbit,2,false,-188.8

then

    yq -p=csv -o=csv '(.[] | select(.name == "Gary") | .numberOfCats) = 3' sample.csv

will output

    name,numberOfCats,likesApples,height
    Gary,3,true,168.8
    Samantha's Rabbit,2,false,-188.8

Formatting Expressions

From version v4.41+

You can put expressions into .yq files, use whitespace and comments to break up complex expressions and explain what’s going on.

  Using expression files and comments

Note that you can execute the file directly - but make sure you make the expression file executable.

Given a sample.yaml file of:

    a:
      b: old

And an `update.yq' expression file of:

    #! yq
    # This is a yq expression that updates the map
    # for several great reasons outlined here.
    .a.b = "new" # line comment here
    | .a.c = "frog"
    # Now good things will happen.

then

    ./update.yq sample.yaml

will output

    a:
      b: new
      c: frog

  Flags in expression files

You can specify flags on the shebang line, this only works when executing the file directly.

Given a sample.yaml file of:

    a:
      b: old

And an `update.yq' expression file of:

    #! yq -oj
    # This is a yq expression that updates the map
    # for several great reasons outlined here.
    .a.b = "new" # line comment here
    | .a.c = "frog"
    # Now good things will happen.

then

    ./update.yq sample.yaml

will output

    {
      "a": {
        "b": "new",
        "c": "frog"
      }
    }

  Commenting out yq expressions

Note that c is no longer set to `frog'. In this example we’re calling yq directly and passing the expression file into --from-file, this is no different from executing the expression file directly.

Given a sample.yaml file of:

    a:
      b: old

And an `update.yq' expression file of:

    #! yq
    # This is a yq expression that updates the map
    # for several great reasons outlined here.
    .a.b = "new" # line comment here
    # | .a.c = "frog"
    # Now good things will happen.

then

    yq --from-file update.yq sample.yml

will output

    a:
      b: new

HCL

Encode and decode to and from HashiCorp Configuration Language (HCL) (https://github.com/hashicorp/hcl).

HCL is commonly used in HashiCorp tools like Terraform for configuration files. The yq HCL encoder and decoder support: - Blocks and attributes - String interpolation and expressions (preserved without quotes) - Comments (leading, head, and line comments) - Nested structures (maps and lists) - Syntax colorisation when enabled

  Parse HCL

Given a sample.hcl file of:

    io_mode = "async"

then

    yq -oy sample.hcl

will output

    io_mode: "async"

  Roundtrip: Sample Doc

Given a sample.hcl file of:

    service "cat" {
      process "main" {
        command = ["/usr/local/bin/awesome-app", "server"]
      }
      process "management" {
        command = ["/usr/local/bin/awesome-app", "management"]
      }
    }

then

    yq sample.hcl

will output

    service "cat" {
      process "main" {
        command = ["/usr/local/bin/awesome-app", "server"]
      }
      process "management" {
        command = ["/usr/local/bin/awesome-app", "management"]
      }
    }

  Roundtrip: With an update

Given a sample.hcl file of:

    service "cat" {
      process "main" {
        command = ["/usr/local/bin/awesome-app", "server"]
      }
      process "management" {
        command = ["/usr/local/bin/awesome-app", "management"]
      }
    }

then

    yq '.service.cat.process.main.command += "meow"' sample.hcl

will output

    service "cat" {
      process "main" {
        command = ["/usr/local/bin/awesome-app", "server", "meow"]
      }
      process "management" {
        command = ["/usr/local/bin/awesome-app", "management"]
      }
    }

  Parse HCL: Sample Doc

Given a sample.hcl file of:

    service "cat" {
      process "main" {
        command = ["/usr/local/bin/awesome-app", "server"]
      }
      process "management" {
        command = ["/usr/local/bin/awesome-app", "management"]
      }
    }

then

    yq -oy sample.hcl

will output

    service:
      cat:
        process:
          main:
            command:
              - "/usr/local/bin/awesome-app"
              - "server"
          management:
            command:
              - "/usr/local/bin/awesome-app"
              - "management"

  Parse HCL: with comments

Given a sample.hcl file of:

    # Configuration
    port = 8080 # server port

then

    yq -oy sample.hcl

will output

    # Configuration
    port: 8080 # server port

  Roundtrip: with comments

Given a sample.hcl file of:

    # Configuration
    port = 8080

then

    yq sample.hcl

will output

    # Configuration
    port = 8080

  Roundtrip: With templates, functions and arithmetic

Given a sample.hcl file of:

    # Arithmetic with literals and application-provided variables
    sum = 1 + addend
    # String interpolation and templates
    message = "Hello, ${name}!"
    # Application-provided functions
    shouty_message = upper(message)

then

    yq sample.hcl

will output

    # Arithmetic with literals and application-provided variables
    sum = 1 + addend
    # String interpolation and templates
    message = "Hello, ${name}!"
    # Application-provided functions
    shouty_message = upper(message)

  Roundtrip: Separate blocks with same name.

Given a sample.hcl file of:

    resource "aws_instance" "web" {
      ami = "ami-12345"
    }
    resource "aws_instance" "db" {
      ami = "ami-67890"
    }

then

    yq sample.hcl

will output

    resource "aws_instance" "web" {
      ami = "ami-12345"
    }
    resource "aws_instance" "db" {
      ami = "ami-67890"
    }

KYaml

Encode and decode to and from KYaml (a restricted subset of YAML that uses flow-style collections).

KYaml is useful when you want YAML data rendered in a compact, JSON-like form while still supporting YAML features like comments.

Notes: - Strings are always double-quoted in KYaml output. - Anchors and aliases are expanded (KYaml output does not emit them).

  Encode kyaml: plain string scalar

Strings are always double-quoted in KYaml output.

Given a sample.yml file of:

    cat

then

    yq -o=kyaml '.' sample.yml

will output

    "cat"

  encode flow mapping and sequence

Given a sample.yml file of:

    a: b
    c:
      - d

then

    yq -o=kyaml '.' sample.yml

will output

    {
      a: "b",
      c: [
        "d",
      ],
    }

  encode non-string scalars

Given a sample.yml file of:

    a: 12
    b: true
    c: null
    d: "true"

then

    yq -o=kyaml '.' sample.yml

will output

    {
      a: 12,
      b: true,
      c: null,
      d: "true",
    }

  quote non-identifier keys

Given a sample.yml file of:

    "1a": b
    "has space": c

then

    yq -o=kyaml '.' sample.yml

will output

    {
      "1a": "b",
      "has space": "c",
    }

  escape quoted strings

Given a sample.yml file of:

    a: "line1\nline2\t\"q\""

then

    yq -o=kyaml '.' sample.yml

will output

    {
      a: "line1\nline2\t\"q\"",
    }

  preserve comments when encoding

Given a sample.yml file of:

    # leading
    a: 1 # a line
    # head b
    b: 2
    c:
      # head d
      - d # d line
      - e
    # trailing

then

    yq -o=kyaml '.' sample.yml

will output

    # leading
    {
      a: 1, # a line
      # head b
      b: 2,
      c: [
        # head d
        "d", # d line
        "e",
      ],
      # trailing
    }

  Encode kyaml: anchors and aliases

KYaml output does not support anchors/aliases; they are expanded to concrete values.

Given a sample.yml file of:

    base: &base
      a: b
    copy: *base

then

    yq -o=kyaml '.' sample.yml

will output

    {
      base: {
        a: "b",
      },
      copy: {
        a: "b",
      },
    }

  Encode kyaml: yaml to kyaml shows formatting differences

KYaml uses flow-style collections (braces/brackets) and explicit commas.

Given a sample.yml file of:

    person:
      name: John
      pets:
        - cat
        - dog

then

    yq -o=kyaml '.' sample.yml

will output

    {
      person: {
        name: "John",
        pets: [
          "cat",
          "dog",
        ],
      },
    }

  Encode kyaml: nested lists of objects

Lists and objects can be nested arbitrarily; KYaml always uses flow-style collections.

Given a sample.yml file of:

    - name: a
      items:
        - id: 1
          tags:
            - k: x
              v: y
            - k: x2
              v: y2
        - id: 2
          tags:
            - k: z
              v: w

then

    yq -o=kyaml '.' sample.yml

will output

    [
      {
        name: "a",
        items: [
          {
            id: 1,
            tags: [
              {
                k: "x",
                v: "y",
              },
              {
                k: "x2",
                v: "y2",
              },
            ],
          },
          {
            id: 2,
            tags: [
              {
                k: "z",
                v: "w",
              },
            ],
          },
        ],
      },
    ]

  Basic input example

Given a sample.lua file of:

    return {
        ["country"] = "Australia"; -- this place
        ["cities"] = {
            "Sydney",
            "Melbourne",
            "Brisbane",
            "Perth",
        };
    };

then

    yq -oy '.' sample.lua

will output

    country: Australia
    cities:
      - Sydney
      - Melbourne
      - Brisbane
      - Perth

  Basic output example

Given a sample.yml file of:

    ---
    country: Australia # this place
    cities:
    - Sydney
    - Melbourne
    - Brisbane
    - Perth

then

    yq -o=lua '.' sample.yml

will output

    return {
        ["country"] = "Australia"; -- this place
        ["cities"] = {
            "Sydney",
            "Melbourne",
            "Brisbane",
            "Perth",
        };
    };

  Unquoted keys

Uses the --lua-unquoted option to produce a nicer-looking output.

Given a sample.yml file of:

    ---
    country: Australia # this place
    cities:
    - Sydney
    - Melbourne
    - Brisbane
    - Perth

then

    yq -o=lua --lua-unquoted '.' sample.yml

will output

    return {
        country = "Australia"; -- this place
        cities = {
            "Sydney",
            "Melbourne",
            "Brisbane",
            "Perth",
        };
    };

  Globals

Uses the --lua-globals option to export the values into the global scope.

Given a sample.yml file of:

    ---
    country: Australia # this place
    cities:
    - Sydney
    - Melbourne
    - Brisbane
    - Perth

then

    yq -o=lua --lua-globals '.' sample.yml

will output

    country = "Australia"; -- this place
    cities = {
        "Sydney",
        "Melbourne",
        "Brisbane",
        "Perth",
    };

  Elaborate example

Given a sample.yml file of:

    ---
    hello: world
    tables:
      like: this
      keys: values
      ? look: non-string keys
      : True
    numbers:
      - decimal: 12345
      - hex: 0x7fabc123
      - octal: 0o30
      - float: 123.45
      - infinity: .inf
        plus_infinity: +.inf
        minus_infinity: -.inf
      - not: .nan

then

    yq -o=lua '.' sample.yml

will output

    return {
        ["hello"] = "world";
        ["tables"] = {
            ["like"] = "this";
            ["keys"] = "values";
            [{
                ["look"] = "non-string keys";
            }] = true;
        };
        ["numbers"] = {
            {
                ["decimal"] = 12345;
            },
            {
                ["hex"] = 0x7fabc123;
            },
            {
                ["octal"] = 24;
            },
            {
                ["float"] = 123.45;
            },
            {
                ["infinity"] = (1/0);
                ["plus_infinity"] = (1/0);
                ["minus_infinity"] = (-1/0);
            },
            {
                ["not"] = (0/0);
            },
        };
    };

Properties

Encode/Decode/Roundtrip to/from a property file. Line comments on value nodes will be copied across.

By default, empty maps and arrays are not encoded - see below for an example on how to encode a value for these.

  Encode properties

Note that empty arrays and maps are not encoded by default.

Given a sample.yml file of:

    # block comments come through
    person: # neither do comments on maps
        name: Mike Wazowski # comments on values appear
        pets:
        - cat # comments on array values appear
        - nested:
            - list entry
        food: [pizza] # comments on arrays do not
    emptyArray: []
    emptyMap: []

then

    yq -o=props sample.yml

will output

    # block comments come through
    # comments on values appear
    person.name = Mike Wazowski
    # comments on array values appear
    person.pets.0 = cat
    person.pets.1.nested.0 = list entry
    person.food.0 = pizza

  Encode properties with array brackets

Declare the –properties-array-brackets flag to give array paths in brackets (e.g. SpringBoot).

Given a sample.yml file of:

    # block comments come through
    person: # neither do comments on maps
        name: Mike Wazowski # comments on values appear
        pets:
        - cat # comments on array values appear
        - nested:
            - list entry
        food: [pizza] # comments on arrays do not
    emptyArray: []
    emptyMap: []

then

    yq -o=props --properties-array-brackets sample.yml

will output

    # block comments come through
    # comments on values appear
    person.name = Mike Wazowski
    # comments on array values appear
    person.pets[0] = cat
    person.pets[1].nested[0] = list entry
    person.food[0] = pizza

  Encode properties - custom separator

Use the –properties-separator flag to specify your own key/value separator.

Given a sample.yml file of:

    # block comments come through
    person: # neither do comments on maps
        name: Mike Wazowski # comments on values appear
        pets:
        - cat # comments on array values appear
        - nested:
            - list entry
        food: [pizza] # comments on arrays do not
    emptyArray: []
    emptyMap: []

then

    yq -o=props --properties-separator=" :@ " sample.yml

will output

    # block comments come through
    # comments on values appear
    person.name :@ Mike Wazowski
    # comments on array values appear
    person.pets.0 :@ cat
    person.pets.1.nested.0 :@ list entry
    person.food.0 :@ pizza

  Encode properties: scalar encapsulation

Note that string values with blank characters in them are encapsulated with double quotes

Given a sample.yml file of:

    # block comments come through
    person: # neither do comments on maps
        name: Mike Wazowski # comments on values appear
        pets:
        - cat # comments on array values appear
        - nested:
            - list entry
        food: [pizza] # comments on arrays do not
    emptyArray: []
    emptyMap: []

then

    yq -o=props --unwrapScalar=false sample.yml

will output

    # block comments come through
    # comments on values appear
    person.name = "Mike Wazowski"
    # comments on array values appear
    person.pets.0 = cat
    person.pets.1.nested.0 = "list entry"
    person.food.0 = pizza

  Encode properties: no comments

Given a sample.yml file of:

    # block comments come through
    person: # neither do comments on maps
        name: Mike Wazowski # comments on values appear
        pets:
        - cat # comments on array values appear
        - nested:
            - list entry
        food: [pizza] # comments on arrays do not
    emptyArray: []
    emptyMap: []

then

    yq -o=props '... comments = ""' sample.yml

will output

    person.name = Mike Wazowski
    person.pets.0 = cat
    person.pets.1.nested.0 = list entry
    person.food.0 = pizza

  Encode properties: include empty maps and arrays

Use a yq expression to set the empty maps and sequences to your desired value.

Given a sample.yml file of:

    # block comments come through
    person: # neither do comments on maps
        name: Mike Wazowski # comments on values appear
        pets:
        - cat # comments on array values appear
        - nested:
            - list entry
        food: [pizza] # comments on arrays do not
    emptyArray: []
    emptyMap: []

then

    yq -o=props '(.. | select( (tag == "!!map" or tag =="!!seq") and length == 0)) = ""' sample.yml

will output

    # block comments come through
    # comments on values appear
    person.name = Mike Wazowski
    # comments on array values appear
    person.pets.0 = cat
    person.pets.1.nested.0 = list entry
    person.food.0 = pizza
    emptyArray =
    emptyMap =

  Decode properties

Given a sample.properties file of:

    # block comments come through
    # comments on values appear
    person.name = Mike Wazowski
    # comments on array values appear
    person.pets.0 = cat
    person.pets.1.nested.0 = list entry
    person.food.0 = pizza

then

    yq -p=props sample.properties

will output

    person:
      # block comments come through
      # comments on values appear
      name: Mike Wazowski
      pets:
        # comments on array values appear
        - cat
        - nested:
            - list entry
      food:
        - pizza

  Decode properties: numbers

All values are assumed to be strings when parsing properties, but you can use the from_yaml operator on all the strings values to autoparse into the correct type.

Given a sample.properties file of:

    a.b = 10

then

    yq -p=props ' (.. | select(tag == "!!str")) |= from_yaml' sample.properties

will output

    a:
      b: 10

  Decode properties - array should be a map

If you have a numeric map key in your property files, use array_to_map to convert them to maps.

Given a sample.properties file of:

    things.10 = mike

then

    yq -p=props '.things |= array_to_map' sample.properties

will output

    things:
      10: mike

  Roundtrip

Given a sample.properties file of:

    # block comments come through
    # comments on values appear
    person.name = Mike Wazowski
    # comments on array values appear
    person.pets.0 = cat
    person.pets.1.nested.0 = list entry
    person.food.0 = pizza

then

    yq -p=props -o=props '.person.pets.0 = "dog"' sample.properties

will output

    # block comments come through
    # comments on values appear
    person.name = Mike Wazowski
    # comments on array values appear
    person.pets.0 = dog
    person.pets.1.nested.0 = list entry
    person.food.0 = pizza

Recipes

These examples are intended to show how you can use multiple operators together so you get an idea of how you can perform complex data manipulation.

Please see the details operator docs (https://mikefarah.gitbook.io/yq/operators) for details on each individual operator.

  Find items in an array

We have an array and we want to find the elements with a particular name.

Given a sample.yml file of:

    - name: Foo
      numBuckets: 0
    - name: Bar
      numBuckets: 0

then

    yq '.[] | select(.name == "Foo")' sample.yml

will output

    name: Foo
    numBuckets: 0

  Explanation:

•   .[] splats the array, and puts all the items in the context.

•   These items are then piped (|) into select(.name == "Foo") which will select all the nodes that have a name property set to `Foo'.

•   See the select (https://mikefarah.gitbook.io/yq/operators/select) operator for more information.

  Find and update items in an array

We have an array and we want to update the elements with a particular name.

Given a sample.yml file of:

    - name: Foo
      numBuckets: 0
    - name: Bar
      numBuckets: 0

then

    yq '(.[] | select(.name == "Foo") | .numBuckets) |= . + 1' sample.yml

will output

    - name: Foo
      numBuckets: 1
    - name: Bar
      numBuckets: 0

  Explanation:

•   Following from the example above.[] splats the array, selects filters the items.

•   We then pipe (|) that into .numBuckets, which will select that field from all the matching items

•   Splat, select and the field are all in brackets, that whole expression is passed to the |= operator as the left hand side expression, with . + 1 as the right hand side expression.

•   |= is the operator that updates fields relative to their own value, which is referenced as dot (.).

•   The expression . + 1 increments the numBuckets counter.

•   See the assign (https://mikefarah.gitbook.io/yq/operators/assign-update) and add (https://mikefarah.gitbook.io/yq/operators/add) operators for more information.

  Deeply prune a tree

Say we are only interested in child1 and child2, and want to filter everything else out.

Given a sample.yml file of:

    parentA:
      - bob
    parentB:
      child1: i am child1
      child3: hiya
    parentC:
      childX: cool
      child2: me child2

then

    yq '(
      .. | # recurse through all the nodes
      select(has("child1") or has("child2")) | # match parents that have either child1 or child2
      (.child1, .child2) | # select those children
      select(.) # filter out nulls
    ) as $i ireduce({};  # using that set of nodes, create a new result map
      setpath($i | path; $i) # and put in each node, using its original path
    )' sample.yml

will output

    parentB:
      child1: i am child1
    parentC:
      child2: me child2

  Explanation:

•   Find all the matching child1 and child2 nodes

•   Using ireduce, create a new map using just those nodes

•   Set each node into the new map using its original path

  Multiple or complex updates to items in an array

We have an array and we want to update the elements with a particular name in reference to its type.

Given a sample.yml file of:

    myArray:
      - name: Foo
        type: cat
      - name: Bar
        type: dog

then

    yq 'with(.myArray[]; .name = .name + " - " + .type)' sample.yml

will output

    myArray:
      - name: Foo - cat
        type: cat
      - name: Bar - dog
        type: dog

  Explanation:

•   The with operator will effectively loop through each given item in the first given expression, and run the second expression against it.

•   .myArray[] splats the array in myArray. So with will run against each item in that array

•   .name = .name + " - " + .type this expression is run against every item, updating the name to be a concatenation of the original name as well as the type.

•   See the with (https://mikefarah.gitbook.io/yq/operators/with) operator for more information and examples.

  Sort an array by a field

Given a sample.yml file of:

    myArray:
      - name: Foo
        numBuckets: 1
      - name: Bar
        numBuckets: 0

then

    yq '.myArray |= sort_by(.numBuckets)' sample.yml

will output

    myArray:
      - name: Bar
        numBuckets: 0
      - name: Foo
        numBuckets: 1

  Explanation:

•   We want to resort .myArray.

•   sort_by works by piping an array into it, and it pipes out a sorted array.

•   So, we use |= to update .myArray. This is the same as doing .myArray = (.myArray | sort_by(.numBuckets))

  Filter, flatten, sort and unique

Lets find the unique set of names from the document.

Given a sample.yml file of:

    - type: foo
      names:
        - Fred
        - Catherine
    - type: bar
      names:
        - Zelda
    - type: foo
      names: Fred
    - type: foo
      names: Ava

then

    yq '[.[] | select(.type == "foo") | .names] | flatten | sort | unique' sample.yml

will output

    - Ava
    - Catherine
    - Fred

  Explanation:

•   .[] | select(.type == "foo") | .names will select the array elements of type “foo”

•   Splat .[] will unwrap the array and match all the items. We need to do this so we can work on the child items, for instance, filter items out using the select operator.

•   But we still want the final results back into an array. So after we’re doing working on the children, we wrap everything back into an array using square brackets around the expression. [.[] | select(.type == "foo") | .names]

•   Now have have an array of all the `names' values. Which includes arrays of strings as well as strings on their own.

•   Pipe | this array through flatten. This will flatten nested arrays. So now we have a flat list of all the name value strings

•   Next we pipe | that through sort and then unique to get a sorted, unique list of the names!

•   See the flatten (https://mikefarah.gitbook.io/yq/operators/flatten), sort (https://mikefarah.gitbook.io/yq/operators/sort) and unique (https://mikefarah.gitbook.io/yq/operators/unique) for more information and examples.

  Export as environment variables (script), or any custom format

Given a yaml document, lets output a script that will configure environment variables with that data. This same approach can be used for exporting into custom formats.

Given a sample.yml file of:

    var0: string0
    var1: string1
    fruit:
      - apple
      - banana
      - peach

then

    yq '.[] |(
        ( select(kind == "scalar") | key + "='\''" + . + "'\''"),
        ( select(kind == "seq") | key + "=(" + (map("'\''" + . + "'\''") | join(",")) + ")")
    )' sample.yml

will output

    var0='string0'
    var1='string1'
    fruit=('apple','banana','peach')

  Explanation:

•   .[] matches all top level elements

•   We need a string expression for each of the different types that will produce the bash syntax, we’ll use the union operator, to join them together

•   Scalars, we just need the key and quoted value: ( select(kind == "scalar") | key + "='" + . + "'")

•   Sequences (or arrays) are trickier, we need to quote each value and join them with ,: map("'" + . + "'") | join(",")

  Custom format with nested data

Like the previous example, but lets handle nested data structures. In this custom example, we’re going to join the property paths with _. The important thing to keep in mind is that our expression is not recursive (despite the data structure being so). Instead we match all elements on the tree and operate on them.

Given a sample.yml file of:

    simple: string0
    simpleArray:
      - apple
      - banana
      - peach
    deep:
      property: value
      array:
        - cat

then

    yq '.. |(
        ( select(kind == "scalar" and parent | kind != "seq") | (path | join("_")) + "='\''" + . + "'\''"),
        ( select(kind == "seq") | (path | join("_")) + "=(" + (map("'\''" + . + "'\''") | join(",")) + ")")
    )' sample.yml

will output

    simple='string0'
    deep_property='value'
    simpleArray=('apple','banana','peach')
    deep_array=('cat')

  Explanation:

•   You’ll need to understand how the previous example works to understand this extension.

•   .. matches all elements, instead of .[] from the previous example that just matches top level elements.

•   Like before, we need a string expression for each of the different types that will produce the bash syntax, we’ll use the union operator, to join them together

•   This time, however, our expression matches every node in the data structure.

•   We only want to print scalars that are not in arrays (because we handle the separately), so well add and parent | kind != "seq" to the select operator expression for scalars

•   We don’t just want the key any more, we want the full path. So instead of key we have path | join("_")

•   The expression for sequences follows the same logic

  Encode shell variables

Note that comments are dropped and values will be enclosed in single quotes as needed.

Given a sample.yml file of:

    # comment
    name: Mike Wazowski
    eyes:
      color: turquoise
      number: 1
    friends:
      - James P. Sullivan
      - Celia Mae

then

    yq -o=shell sample.yml

will output

    name='Mike Wazowski'
    eyes_color=turquoise
    eyes_number=1
    friends_0='James P. Sullivan'
    friends_1='Celia Mae'

  Encode shell variables: illegal variable names as key.

Keys that would be illegal as variable keys are adapted.

Given a sample.yml file of:

    ascii_=_symbols: replaced with _
    "ascii_ _controls": dropped (this example uses \t)
    nonascii_א_characters: dropped
    effort_expeñded_tò_preserve_accented_latin_letters: moderate (via unicode NFKD)

then

    yq -o=shell sample.yml

will output

    ascii___symbols='replaced with _'
    ascii__controls='dropped (this example uses \t)'
    nonascii__characters=dropped
    effort_expended_to_preserve_accented_latin_letters='moderate (via unicode NFKD)'

  Encode shell variables: empty values, arrays and maps

Empty values are encoded to empty variables, but empty arrays and maps are skipped.

Given a sample.yml file of:

    empty:
      value:
      array: []
      map:   {}

then

    yq -o=shell sample.yml

will output

    empty_value=

  Encode shell variables: single quotes in values

Single quotes in values are encoded as `“'“’ (close single quote, double-quoted single quote, open single quote).

Given a sample.yml file of:

    name: Miles O'Brien

then

    yq -o=shell sample.yml

will output

    name='Miles O'"'"'Brien'

  Encode shell variables: custom separator

Use –shell-key-separator to specify a custom separator between keys. This is useful when the original keys contain underscores.

Given a sample.yml file of:

    my_app:
      db_config:
        host: localhost
        port: 5432

then

    yq -o=shell --shell-key-separator="__" sample.yml

will output

    my_app__db_config__host=localhost
    my_app__db_config__port=5432

TOML

Decode from TOML. Note that yq does not yet support outputting in TOML format (and therefore it cannot roundtrip)

  Parse: Simple

Given a sample.toml file of:

    A = "hello"
    B = 12

then

    yq -oy '.' sample.toml

will output

    A: hello
    B: 12

  Parse: Deep paths

Given a sample.toml file of:

    person.name = "hello"
    person.address = "12 cat st"

then

    yq -oy '.' sample.toml

will output

    person:
      name: hello
      address: 12 cat st

  Encode: Scalar

Given a sample.toml file of:

    person.name = "hello"
    person.address = "12 cat st"

then

    yq '.person.name' sample.toml

will output

    hello

  Parse: inline table

Given a sample.toml file of:

    name = { first = "Tom", last = "Preston-Werner" }

then

    yq -oy '.' sample.toml

will output

    name:
      first: Tom
      last: Preston-Werner

  Parse: Array Table

Given a sample.toml file of:

    [owner.contact]
    name = "Tom Preston-Werner"
    age = 36
    [[owner.addresses]]
    street = "first street"
    suburb = "ok"
    [[owner.addresses]]
    street = "second street"
    suburb = "nice"

then

    yq -oy '.' sample.toml

will output

    owner:
      contact:
        name: Tom Preston-Werner
        age: 36
      addresses:
        - street: first street
          suburb: ok
        - street: second street
          suburb: nice

  Parse: Array of Array Table

Given a sample.toml file of:

    [[fruits]]
    name = "apple"
    [[fruits.varieties]]  # nested array of tables
    name = "red delicious"

then

    yq -oy '.' sample.toml

will output

    fruits:
      - name: apple
        varieties:
          - name: red delicious

  Parse: Empty Table

Given a sample.toml file of:

    [dependencies]

then

    yq -oy '.' sample.toml

will output

    dependencies: {}

  Roundtrip: inline table attribute

Given a sample.toml file of:

    name = { first = "Tom", last = "Preston-Werner" }

then

    yq '.' sample.toml

will output

    name = { first = "Tom", last = "Preston-Werner" }

  Roundtrip: table section

Given a sample.toml file of:

    [owner.contact]
    name = "Tom"
    age = 36

then

    yq '.' sample.toml

will output

    [owner.contact]
    name = "Tom"
    age = 36

  Roundtrip: array of tables

Given a sample.toml file of:

    [[fruits]]
    name = "apple"
    [[fruits.varieties]]
    name = "red delicious"

then

    yq '.' sample.toml

will output

    [[fruits]]
    name = "apple"
    [[fruits.varieties]]
    name = "red delicious"

  Roundtrip: arrays and scalars

Given a sample.toml file of:

    A = ["hello", ["world", "again"]]
    B = 12

then

    yq '.' sample.toml

will output

    A = ["hello", ["world", "again"]]
    B = 12

  Roundtrip: simple

Given a sample.toml file of:

    A = "hello"
    B = 12

then

    yq '.' sample.toml

will output

    A = "hello"
    B = 12

  Roundtrip: deep paths

Given a sample.toml file of:

    [person]
    name = "hello"
    address = "12 cat st"

then

    yq '.' sample.toml

will output

    [person]
    name = "hello"
    address = "12 cat st"

  Roundtrip: empty array

Given a sample.toml file of:

    A = []

then

    yq '.' sample.toml

will output

    A = []

  Roundtrip: sample table

Given a sample.toml file of:

    var = "x"
    [owner.contact]
    name = "Tom Preston-Werner"
    age = 36

then

    yq '.' sample.toml

will output

    var = "x"
    [owner.contact]
    name = "Tom Preston-Werner"
    age = 36

  Roundtrip: empty table

Given a sample.toml file of:

    [dependencies]

then

    yq '.' sample.toml

will output

    [dependencies]

  Roundtrip: comments

Given a sample.toml file of:

    # This is a comment
    A = "hello"  # inline comment
    B = 12
    # Table comment
    [person]
    name = "Tom"  # name comment

then

    yq '.' sample.toml

will output

    # This is a comment
    A = "hello"  # inline comment
    B = 12
    # Table comment
    [person]
    name = "Tom"  # name comment

  Roundtrip: sample from web

Given a sample.toml file of:

    # This is a TOML document
    title = "TOML Example"
    [owner]
    name = "Tom Preston-Werner"
    dob = 1979-05-27T07:32:00-08:00
    [database]
    enabled = true
    ports = [8000, 8001, 8002]
    data = [["delta", "phi"], [3.14]]
    temp_targets = { cpu = 79.5, case = 72.0 }
    # [servers] yq can't do this one yet
    [servers.alpha]
    ip = "10.0.0.1"
    role = "frontend"
    [servers.beta]
    ip = "10.0.0.2"
    role = "backend"

then

    yq '.' sample.toml

will output

    # This is a TOML document
    title = "TOML Example"
    [owner]
    name = "Tom Preston-Werner"
    dob = 1979-05-27T07:32:00-08:00
    [database]
    enabled = true
    ports = [8000, 8001, 8002]
    data = [["delta", "phi"], [3.14]]
    temp_targets = { cpu = 79.5, case = 72.0 }
    # [servers] yq can't do this one yet
    [servers.alpha]
    ip = "10.0.0.1"
    role = "frontend"
    [servers.beta]
    ip = "10.0.0.2"
    role = "backend"

  Encode: Simple mapping produces table section

Given a sample.yml file of:

    arg:
      hello: foo

then

    yq -o toml '.' sample.yml

will output

    [arg]
    hello = "foo"

XML

Encode and decode to and from XML. Whitespace is not conserved for round trips - but the order of the fields are.

Consecutive xml nodes with the same name are assumed to be arrays.

XML content data, attributes processing instructions and directives are all created as plain fields.

This can be controlled by:

Flag | Default | Sample XML
--xml-attribute-prefix | + (changing to +@ soon) | Legs in <cat legs="4"/>
--xml-content-name | +content | Meow in <cat>Meow <fur>true</true></cat>
--xml-directive-name | +directive | <!DOCTYPE config system "blah">
--xml-proc-inst-prefix | +p_ | <?xml version="1"?>

{% hint style=“warning” %} Default Attribute Prefix will be changing in v4.30! In order to avoid name conflicts (e.g. having an attribute named “content” will create a field that clashes with the default content name of “+content”) the attribute prefix will be changing to “+@”.

This will affect users that have not set their own prefix and are not roundtripping XML changes.

{% endhint %}

  Encoder / Decoder flag options

In addition to the above flags, there are the following xml encoder/decoder options controlled by flags:

Flag | Default | Description
--xml-strict-mode | false | Strict mode enforces the requirements of the XML specification. When switched off the parser allows input containing common mistakes. See the Golang xml decoder (https://pkg.go.dev/encoding/xml#Decoder) for more details.
--xml-keep-namespace | true | Keeps the namespace of attributes
--xml-raw-token | true | Does not verify that start and end elements match and does not translate name space prefixes to their corresponding URLs.
--xml-skip-proc-inst | false | Skips over processing instructions, e.g. <?xml version="1"?>
--xml-skip-directives | false | Skips over directives, e.g. <!DOCTYPE config system "blah">

See below for examples

  Parse xml: simple

Notice how all the values are strings, see the next example on how you can fix that.

Given a sample.xml file of:

    <?xml version="1.0" encoding="UTF-8"?>
    <cat>
      <says>meow</says>
      <legs>4</legs>
      <cute>true</cute>
    </cat>

then

    yq -oy sample.xml

will output

    +p_xml: version="1.0" encoding="UTF-8"
    cat:
      says: meow
      legs: "4"
      cute: "true"

  Parse xml: number

All values are assumed to be strings when parsing XML, but you can use the from_yaml operator on all the strings values to autoparse into the correct type.

Given a sample.xml file of:

    <?xml version="1.0" encoding="UTF-8"?>
    <cat>
      <says>meow</says>
      <legs>4</legs>
      <cute>true</cute>
    </cat>

then

    yq -oy ' (.. | select(tag == "!!str")) |= from_yaml' sample.xml

will output

    +p_xml: version="1.0" encoding="UTF-8"
    cat:
      says: meow
      legs: 4
      cute: true

  Parse xml: array

Consecutive nodes with identical xml names are assumed to be arrays.

Given a sample.xml file of:

    <?xml version="1.0" encoding="UTF-8"?>
    <animal>cat</animal>
    <animal>goat</animal>

then

    yq -oy sample.xml

will output

    +p_xml: version="1.0" encoding="UTF-8"
    animal:
      - cat
      - goat

  Parse xml: force as an array

In XML, if your array has a single item, then yq doesn’t know its an array. This is how you can consistently force it to be an array. This handles the 3 scenarios of having nothing in the array, having a single item and having multiple.

Given a sample.xml file of:

    <zoo><animal>cat</animal></zoo>

then

    yq -oy '.zoo.animal |= ([] + .)' sample.xml

will output

    zoo:
      animal:
        - cat

  Parse xml: force all as an array

Given a sample.xml file of:

    <zoo><thing><frog>boing</frog></thing></zoo>

then

    yq -oy '.. |= [] + .' sample.xml

will output

    - zoo:
        - thing:
            - frog:
                - boing

  Parse xml: attributes

Attributes are converted to fields, with the default attribute prefix `+'. Use ’–xml-attribute-prefix` to set your own.

Given a sample.xml file of:

    <?xml version="1.0" encoding="UTF-8"?>
    <cat legs="4">
      <legs>7</legs>
    </cat>

then

    yq -oy sample.xml

will output

    +p_xml: version="1.0" encoding="UTF-8"
    cat:
      +@legs: "4"
      legs: "7"

  Parse xml: attributes with content

Content is added as a field, using the default content name of +content. Use --xml-content-name to set your own.

Given a sample.xml file of:

    <?xml version="1.0" encoding="UTF-8"?>
    <cat legs="4">meow</cat>

then

    yq -oy sample.xml

will output

    +p_xml: version="1.0" encoding="UTF-8"
    cat:
      +content: meow
      +@legs: "4"

  Parse xml: content split between comments/children

Multiple content texts are collected into a sequence.

Given a sample.xml file of:

    <root>  value  <!-- comment-->anotherValue <a>frog</a> cool!</root>

then

    yq -oy sample.xml

will output

    root:
      +content: # comment
        - value
        - anotherValue
        - cool!
      a: frog

  Parse xml: custom dtd

DTD entities are processed as directives.

Given a sample.xml file of:

    <?xml version="1.0"?>
    <!DOCTYPE root [
    <!ENTITY writer "Blah.">
    <!ENTITY copyright "Blah">
    ]>
    <root>
        <item>&writer;&copyright;</item>
    </root>

then

    yq sample.xml

will output

    <?xml version="1.0"?>
    <!DOCTYPE root [
    <!ENTITY writer "Blah.">
    <!ENTITY copyright "Blah">
    ]>
    <root>
      <item>&amp;writer;&amp;copyright;</item>
    </root>

  Parse xml: skip custom dtd

DTDs are directives, skip over directives to skip DTDs.

Given a sample.xml file of:

    <?xml version="1.0"?>
    <!DOCTYPE root [
    <!ENTITY writer "Blah.">
    <!ENTITY copyright "Blah">
    ]>
    <root>
        <item>&writer;&copyright;</item>
    </root>

then

    yq --xml-skip-directives sample.xml

will output

    <?xml version="1.0"?>
    <root>
      <item>&amp;writer;&amp;copyright;</item>
    </root>

  Parse xml: with comments

A best attempt is made to preserve comments.

Given a sample.xml file of:

    <!-- before cat -->
    <cat>
        <!-- in cat before -->
        <x>3<!-- multi
    line comment
    for x --></x>
        <!-- before y -->
        <y>
            <!-- in y before -->
            <d><!-- in d before -->z<!-- in d after --></d>

            <!-- in y after -->
        </y>
        <!-- in_cat_after -->
    </cat>
    <!-- after cat -->

then

    yq -oy sample.xml

will output

    # before cat
    cat:
      # in cat before
      x: "3" # multi
      # line comment
      # for x
      # before y
      y:
        # in y before
        # in d before
        d: z # in d after
        # in y after
      # in_cat_after
    # after cat

  Parse xml: keep attribute namespace

Defaults to true

Given a sample.xml file of:

    <?xml version="1.0"?>
    <map xmlns="some-namespace" xmlns:xsi="some-instance" xsi:schemaLocation="some-url">
      <item foo="bar">baz</item>
      <xsi:item>foobar</xsi:item>
    </map>

then

    yq --xml-keep-namespace=false sample.xml

will output

    <?xml version="1.0"?>
    <map xmlns="some-namespace" xsi="some-instance" schemaLocation="some-url">
      <item foo="bar">baz</item>
      <item>foobar</item>
    </map>

instead of

    <?xml version="1.0"?>
    <map xmlns="some-namespace" xmlns:xsi="some-instance" xsi:schemaLocation="some-url">
      <item foo="bar">baz</item>
      <xsi:item>foobar</xsi:item>
    </map>

  Parse xml: keep raw attribute namespace

Defaults to true

Given a sample.xml file of:

    <?xml version="1.0"?>
    <map xmlns="some-namespace" xmlns:xsi="some-instance" xsi:schemaLocation="some-url">
      <item foo="bar">baz</item>
      <xsi:item>foobar</xsi:item>
    </map>

then

    yq --xml-raw-token=false sample.xml

will output

    <?xml version="1.0"?>
    <some-namespace:map xmlns="some-namespace" xmlns:xsi="some-instance" some-instance:schemaLocation="some-url">
      <some-namespace:item foo="bar">baz</some-namespace:item>
      <some-instance:item>foobar</some-instance:item>
    </some-namespace:map>

instead of

    <?xml version="1.0"?>
    <map xmlns="some-namespace" xmlns:xsi="some-instance" xsi:schemaLocation="some-url">
      <item foo="bar">baz</item>
      <xsi:item>foobar</xsi:item>
    </map>

  Encode xml: simple

Given a sample.yml file of:

    cat: purrs

then

    yq -o=xml sample.yml

will output

    <cat>purrs</cat>

  Encode xml: array

Given a sample.yml file of:

    pets:
      cat:
        - purrs
        - meows

then

    yq -o=xml sample.yml

will output

    <pets>
      <cat>purrs</cat>
      <cat>meows</cat>
    </pets>

  Encode xml: attributes

Fields with the matching xml-attribute-prefix are assumed to be attributes.

Given a sample.yml file of:

    cat:
      +@name: tiger
      meows: true

then

    yq -o=xml sample.yml

will output

    <cat name="tiger">
      <meows>true</meows>
    </cat>

  Encode xml: attributes with content

Fields with the matching xml-content-name is assumed to be content.

Given a sample.yml file of:

    cat:
      +@name: tiger
      +content: cool

then

    yq -o=xml sample.yml

will output

    <cat name="tiger">cool</cat>

  Encode xml: comments

A best attempt is made to copy comments to xml.

Given a sample.yml file of:

    #
    # header comment
    # above_cat
    #
    cat: # inline_cat
      # above_array
      array: # inline_array
        - val1 # inline_val1
        # above_val2
        - val2 # inline_val2
    # below_cat

then

    yq -o=xml sample.yml

will output

    <!--
    header comment
    above_cat
    -->
    <!-- inline_cat -->
    <cat><!-- above_array inline_array -->
      <array>val1<!-- inline_val1 --></array>
      <array><!-- above_val2 -->val2<!-- inline_val2 --></array>
    </cat><!-- below_cat -->

  Encode: doctype and xml declaration

Use the special xml names to add/modify proc instructions and directives.

Given a sample.yml file of:

    +p_xml: version="1.0"
    +directive: 'DOCTYPE config SYSTEM "/etc/iwatch/iwatch.dtd" '
    apple:
      +p_coolioo: version="1.0"
      +directive: 'CATYPE meow purr puss '
      b: things

then

    yq -o=xml sample.yml

will output

    <?xml version="1.0"?>
    <!DOCTYPE config SYSTEM "/etc/iwatch/iwatch.dtd" >
    <apple><?coolioo version="1.0"?><!CATYPE meow purr puss >
      <b>things</b>
    </apple>

  Round trip: with comments

A best effort is made, but comment positions and white space are not preserved perfectly.

Given a sample.xml file of:

    <!-- before cat -->
    <cat>
        <!-- in cat before -->
        <x>3<!-- multi
    line comment
    for x --></x>
        <!-- before y -->
        <y>
            <!-- in y before -->
            <d><!-- in d before -->z<!-- in d after --></d>

            <!-- in y after -->
        </y>
        <!-- in_cat_after -->
    </cat>
    <!-- after cat -->

then

    yq sample.xml

will output

    <!-- before cat -->
    <cat><!-- in cat before -->
      <x>3<!-- multi
    line comment
    for x --></x><!-- before y -->
      <y><!-- in y before
    in d before -->
        <d>z<!-- in d after --></d><!-- in y after -->
      </y><!-- in_cat_after -->
    </cat><!-- after cat -->

  Roundtrip: with doctype and declaration

yq parses XML proc instructions and directives into nodes. Unfortunately the underlying XML parser loses whitespace information.

Given a sample.xml file of:

    <?xml version="1.0"?>
    <!DOCTYPE config SYSTEM "/etc/iwatch/iwatch.dtd" >
    <apple>
      <?coolioo version="1.0"?>
      <!CATYPE meow purr puss >
      <b>things</b>
    </apple>

then

    yq sample.xml

will output

    <?xml version="1.0"?>
    <!DOCTYPE config SYSTEM "/etc/iwatch/iwatch.dtd" >
    <apple><?coolioo version="1.0"?><!CATYPE meow purr puss >
      <b>things</b>
    </apple>

AUTHORS
Mike Farah.