Synopsis

#include <pcre2.h>

int pcre2_substitute(const pcre2_code *code, PCRE2_SPTR subject,
                     PCRE2_SIZE length, PCRE2_SIZE start_offset,
                     uint32_t options, pcre2_match_data *match_data,
                     pcre2_match_context *mcontext,
                     PCRE2_SPTR replacement, PCRE2_SIZE rlength,
                     PCRE2_UCHAR *buffer, PCRE2_SIZE *blength);

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

start_offset

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

buffer

Points to the output buffer, or may be NULL if blength is zero

blength

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, start_offset and rlength values are code units, not characters, as is the contents of the variable pointed at by blength. 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.