pcre2_substring_get_bynumber (3) - Linux Manuals
pcre2_substring_get_bynumber: Perl-compatible regular expressions (revised API)
PCRE2 - Perl-compatible regular expressions (revised API)
int pcre2_substring_get_bynumber(pcre2_match_data *match_data, uint32_t number, PCRE2_UCHAR **bufferptr, PCRE2_SIZE *bufflen);
This is a convenience function for extracting a captured substring by number into newly acquired memory. The arguments are:
The memory in which the substring is placed is obtained by calling the same memory allocation function that was used for the match data block. The convenience function pcre2_substring_free() can be used to free it when it is no longer needed. The yield of the function is zero for success or one of the following error numbers:
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.