---
name: "pcre2_substitute"
section: "3"
platform: "linux"
package: "pcre2"
version: "10.49-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/pcre2_substitute"
---

# pcre2\_substitute(3)

Perl-compatible regular expressions (revised API)

## NAME

PCRE2 - Perl-compatible regular expressions (revised API)

## 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.