PCRE - Perl-compatible regular expressions
int pcre_copy_substring(const char *subject, int *ovector, int stringcount, int stringnumber, char *buffer, int buffersize);
This is a convenience function for extracting a captured substring into a given buffer. The arguments are:
subject Subject that has been successfully matched
ovector Offset vector that pcre_exec() used
stringcount Value returned by pcre_exec()
stringnumber Number of the required substring
buffer Buffer to receive the string
buffersize Size of buffer
The yield is the legnth of the string, PCRE_ERROR_NOMEMORY if the buffer was too small, or PCRE_ERROR_NOSUBSTRING if the string number 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.