PCRE2\_SUBSTITUTE(3) Library Functions Manual PCRE2\_SUBSTITUTE(3)

# [NAME](#NAME)

PCRE2 - Perl-compatible regular expressions (revised API)

# [SYNOPSIS](#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](#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.

03 October 2025 PCRE2 10.49

---

Document: pcre2_substitute(3) from pcre2 10.49-r2 (Chainguard OS)
Source: https://github.com/PCRE2Project/pcre2.git