PCRE2 - Perl-compatible regular expressions (revised API) .rs #include <pcre2.h>

 int pcre2_substring_get_bynumber(pcre2_match_data *match_data,  " uint32_t number, PCRE2_UCHAR **bufferptr, PCRE2_SIZE *bufflen);" 

. .rs This is a convenience function for extracting a captured substring by number into newly acquired memory. The arguments are: match_data The match data for the match number Number of the required substring bufferptr Where to put the string pointer bufflen Where to put the string length 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: PCRE2_ERROR_NOSUBSTRING there are no groups of that number PCRE2_ERROR_UNAVAILBLE the ovector was too small for that group PCRE2_ERROR_UNSET the group did not participate in the match PCRE2_ERROR_NOMEMORY memory could not be obtained

There is a complete description of the PCRE2 native API in the HREF
pcre2api
page and a description of the POSIX API in the HREF
pcre2posix
page.