# 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 context is needed only if you want to:

      Set up a callout function
      Change the limit for calling the internal function match()
      Change the limit for calling match() recursively
      Set custom memory management when the heap is used for recursion

The length, startoffset and rlength values are code units, not characters, as is the contents of the variable pointed at by outlengthptr, which is updated to the actual length of the new string. The options are:

      PCRE2_ANCHORED             Match only at the first position
      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_UTF_CHECK         Do not check the subject or replacement
                                  for UTF validity (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_OVERFLOW_LENGTH  If overflow, compute needed length
      PCRE2_SUBSTITUTE_UNKNOWN_UNSET  Treat unknown group as unset
      PCRE2_SUBSTITUTE_UNSET_EMPTY  Simple unset insert = empty string

The function returns the number of substitutions, which may be zero if there were no matches. The result can 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.

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