// URL that generated this code:
// http://txt2re.com/index-cpcre.php3?s=42%2043&2&3&9999

#include <stdio.h>
#include <string.h>
#include <pcre.h>

int main(int argc, char **argv)
{
  const char *error;
  int erroffset;
  int ovector[186];
  char re[8192]="";
  char txt[]="42 43";

  char re1[]="";	//  1
  strcat(re,re1);
  char re2[]=".*?";	// Non-greedy match on filler
  strcat(re,re2);
  char re3[]="(?:(?:[0-2]?\\d{1})|(?:[3][01]{1}))(?![\\d])";	// Uninteresting: day
  strcat(re,re3);
  char re4[]="((?:(?:[0-2]?\\d{1})|(?:[3][01]{1})))(?![\\d])";	// Day 1
  strcat(re,re4);
  char re5[]=".*?";	// Non-greedy match on filler
  strcat(re,re5);
  char re6[]="(\\d+)";	// Integer Number 1
  strcat(re,re6);

  pcre *r =  pcre_compile(re, PCRE_CASELESS|PCRE_DOTALL, &error, &erroffset, NULL);
  int rc = pcre_exec(r, NULL, txt, strlen(txt), 0, 0, ovector, 186);
  if (rc>0)
  {
      char 1[1024];
      pcre_copy_substring(txt, ovector, rc,1,1, 1024);
      printf("(%s)",1);
      char day1[1024];
      pcre_copy_substring(txt, ovector, rc,2,day1, 1024);
      printf("(%s)",day1);
      char int1[1024];
      pcre_copy_substring(txt, ovector, rc,3,int1, 1024);
      printf("(%s)",int1);
      puts("\n");
  }
}

//-----
// C does not provide a regular expression feature as standard.
//
// To run this code you will need to first download and install
// the PCRE library from http://www.pcre.org/
//
// Note that on Linux systems PCRE is often already installed in /usr/lib/libpcre* or /usr/local/lib/libpcre*. 
//
// Compile and on Unix using:
// # gcc -lpcre x.c
// # ./a.out
//