#include <pcre.h>
int pcre_get_stringnumber(const pcre *code,
const char *name);
This convenience function finds the number of a named substring capturing parenthesis in a compiled pattern. Its arguments are:
code Compiled regular expression
name Name whose number is required
The yield of the function is the number of the parenthesis if the name is found, or PCRE_ERROR_NOSUBSTRING otherwise.
There is a complete description of the PCRE API in the pcreapi page.