PCRE2 - Perl-compatible regular expressions (revised API)
#include <pcre2.h>
PCRE2_SIZE pcre2_get_startchar(pcre2_match_data *match_data);
After a successful call of pcre2_match() that was passed the match block
that is this function's argument, this function returns the code unit offset
of the character at which the successful match started. For a non-partial
match, this can be different to the value of ovector[0] if the pattern
contains the \K escape sequence. After a partial match, however, this value is
always the same as ovector[0] because \K does not affect the result of
a partial match.
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.