Regex example in c

extract_value.c

#include <stdio.h>
#include <stdlib.h>
#include <regex.h>

char *extract_value(char *string, char *pattern)
{
  int begin, end, length, i, w=0;
  char *word = NULL;
  regex_t    regex;
  regmatch_t match[2];
  regcomp(&regex, pattern, REG_EXTENDED);
  if ((regexec(&regex, string, 2, match, 0)) == 0)
  {
    begin  = (int)match[1].rm_so;
    end    = (int)match[1].rm_eo;
    length = end - begin;
    word   = malloc(length+1);
    for (i = begin; i < end; i++)
    {
      word[w] = string[i];
      w++;
    }
    word[w] = 0;
  }
  regfree(&regex);
  return word;
}

int main() {
  char *match = extract_value("xoffset=0     yoffset=-4    xadvance=5", "yoffset=([-0-9]+)");
  printf("%s\n", match);
	return 0;
}