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

 int pcre2_substring_length_byname(pcre2_match_data *match_data,  " PCRE2_SPTR name, PCRE2_SIZE *length);" 

. .rs This function returns the length of a matched substring, identified by name. The arguments are: match_data The match data block for the match name The substring name length Where to return the length The yield is zero on success, or an error code if the substring is not found.

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.