# pcre2_substitute man page

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## SYNOPSIS

#include <pcre2.h>

int pcre2_substitute(const pcre2_code *code, PCRE2_SPTR subject, PCRE2_SIZE length, PCRE2_SIZE startoffset, uint32_t options, pcre2_match_data *match_data, pcre2_match_context *mcontext, PCRE2_SPTR replacement, PCRE2_SIZE rlength, PCRE2_UCHAR *outputbuffer, PCRE2_SIZE *outlengthptr);

## DESCRIPTION

This function matches a compiled regular expression against a given subject string, using a matching algorithm that is similar to Perl's. It then makes a copy of the subject, substituting a replacement string for what was matched. Its arguments are:

      code          Points to the compiled pattern
      subject       Points to the subject string
      length        Length of the subject string
      startoffset   Offset in the subject at which to start matching
      options       Option bits
      match_data    Points to a match data block, or is NULL
      mcontext      Points to a match context, or is NULL
      replacement   Points to the replacement string
      rlength       Length of the replacement string
      outputbuffer  Points to the output buffer
      outlengthptr  Points to the length of the output buffer

A match data block is needed only if you want to inspect the data from the final match that is returned in that block or if PCRE2_SUBSTITUTE_MATCHED is set. A match context is needed only if you want to:

      Set up a callout function
      Set a matching offset limit
      Change the backtracking match limit
      Change the backtracking depth limit
      Set custom memory management in the match context

The length, startoffset and rlength values are code units, not characters, as is the contents of the variable pointed at by outlengthptr. This variable must contain the length of the output buffer when the function is called. If the function is successful, the value is changed to the length of the new string, excluding the trailing zero that is automatically added.

The subject and replacement lengths can be given as PCRE2_ZERO_TERMINATED for zero-terminated strings. The options are:

      PCRE2_ANCHORED                     Match only at the first position
      PCRE2_ENDANCHORED                  Match only at end of subject
      PCRE2_NOTBOL                       Subject is not the beginning of a line
      PCRE2_NOTEOL                       Subject is not the end of a line
      PCRE2_NOTEMPTY                     An empty string is not a valid match
      PCRE2_NOTEMPTY_ATSTART             An empty string at the start of the subject is not a valid match
      PCRE2_NO_JIT                       Do not use JIT matching
      PCRE2_NO_UTF_CHECK                 Do not check for UTF validity in the subject or replacement
                                          (only relevant if PCRE2_UTF was set at compile time)
      PCRE2_SUBSTITUTE_EXTENDED          Do extended replacement processing
      PCRE2_SUBSTITUTE_GLOBAL            Replace all occurrences in the subject
      PCRE2_SUBSTITUTE_LITERAL           The replacement string is literal
      PCRE2_SUBSTITUTE_MATCHED           Use pre-existing match data for first match
      PCRE2_SUBSTITUTE_OVERFLOW_LENGTH   If overflow, compute needed length
      PCRE2_SUBSTITUTE_REPLACEMENT_ONLY  Return only replacement string(s)
      PCRE2_SUBSTITUTE_UNKNOWN_UNSET     Treat unknown group as unset
      PCRE2_SUBSTITUTE_UNSET_EMPTY       Simple unset insert = empty string

If PCRE2_SUBSTITUTE_LITERAL is set, PCRE2_SUBSTITUTE_EXTENDED, PCRE2_SUBSTITUTE_UNKNOWN_UNSET, and PCRE2_SUBSTITUTE_UNSET_EMPTY are ignored.

If PCRE2_SUBSTITUTE_MATCHED is set, match_data must be non-NULL; its contents must be the result of a call to pcre2_match() (or pcre2_jit_match()) using the same pattern, subject pointer, effective subject length, start offset, and match options.

The function returns the number of substitutions, which may be zero if there are no matches. The result may be greater than one only when PCRE2_SUBSTITUTE_GLOBAL is set. In the event of an error, a negative error code is returned.

There is a complete description of the PCRE2 native API in the pcre2api page and a description of the POSIX API in the pcre2posix page.

Return to the PCRE2 index page.