Regular Expressions (REGEX) in C languague

https://www.ibm.com/support/knowledgecenter/en/ssw_ibm_i_72/rtref/regexec.htm

ftp://ftp.gnu.org/old-gnu/Manuals/glibc-2.2.3/html_chapter/libc_10.html

#include <regex.h>

#include <stdio.h>

#include <stdlib.h>

int main(void)

{

   regex_t    preg;

   char       *string = "a very simple simple simple string";

   char       *pattern = "\\(sim[a-z]le\\) \\1";

   int        rc;

   size_t     nmatch = 2;

   regmatch_t pmatch[2];

   if (0 != (rc = regcomp(&preg, pattern, 0))) {

      printf("regcomp() failed, returning nonzero (%d)\n", rc);

      exit(EXIT_FAILURE);

   }

   if (0 != (rc = regexec(&preg, string, nmatch, pmatch, 0))) {

      printf("Failed to match '%s' with '%s',returning %d.\n",

             string, pattern, rc);

   }

   else {

      printf("With the whole expression, "

             "a matched substring \"%.*s\" is found at position %d to %d.\n",

             pmatch[0].rm_eo - pmatch[0].rm_so, &string[pmatch[0].rm_so],

             pmatch[0].rm_so, pmatch[0].rm_eo - 1);

      printf("With the sub-expression, "

             "a matched substring \"%.*s\" is found at position %d to %d.\n",

             pmatch[1].rm_eo - pmatch[1].rm_so, &string[pmatch[1].rm_so],

             pmatch[1].rm_so, pmatch[1].rm_eo - 1);

   }

   regfree(&preg);

   return 0;

   /****************************************************************************

      The output should be similar to :

      With the whole expression, a matched substring "simple simple" is found

      at position 7 to 19.

      With the sub-expression, a matched substring "simple" is found

      at position 7 to 12.

   ****************************************************************************/

}