PCRE

#include <pcre.h>

int pcre_get_named_substring(const pcre *code, const char *subject, int *ovector, int stringcount, const char *stringname, const char **stringptr);

int pcre16_get_named_substring(const pcre16 *code, PCRE_SPTR16 subject, int *ovector, int stringcount, PCRE_SPTR16 stringname, PCRE_SPTR16 *stringptr);

This is a convenience function for extracting a captured substring by name. The arguments are:

code Compiled pattern
subject Subject that has been successfully matched
ovector Offset vector that pcre[16]_exec() used
stringcount Value returned by pcre[16]_exec()
stringname Name of the required substring
stringptr Where to put the string pointer

The memory in which the substring is placed is obtained by calling pcre[16]_malloc(). The convenience function pcre[16]_free_substring() can be used to free it when it is no longer needed. The yield of the function is the length of the extracted substring, PCRE_ERROR_NOMEMORY if sufficient memory could not be obtained, or PCRE_ERROR_NOSUBSTRING if the string name is invalid.

There is a complete description of the PCRE native API in the pcreapi page and a description of the POSIX API in the pcreposix page.