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From: hollombe@ttidca.TTI.COM (The Polymath)
Newsgroups: alt.hackers
Subject: Useful string function
Message-ID: <27187@ttidca.TTI.COM>
Date: 25 Jun 91 23:33:05 GMT
Organization: The Cat Factory
Lines: 62
Approved: yes

Here's a simple minor hack I threw together.  It's proved so useful, I'm
amazed it isn't part of the standard Unix libraries. (C'mon.  Even BASIC
does this)!  Anyway, it's a function that finds a substring within a
string and returns its starting location or -1 if the substring isn't
there.  I'm sure you can think of many variations and improvements.  This
version does what I need it to.  Enjoy.

int Strloc (s1, s2)
char *s1;           /* String to be searched */
char *s2;           /* String to search for  */
{

               /*****************************************/
               /* Locate substring s2 within string s1. */
               /* Return starting position of s2.       */
               /* Return -1 if s2 not found in s1.      */
               /*                                       */
	       /* Requires stdio.h.                     */
	       /* Calls strlen().                       */
               /*                                       */
	       /* Placed in public domain 25 June 1991  */
	       /*                  by                   */
	       /*       G. Hollombe (The Polymath)      */
               /*****************************************/

     register int i, j;       /* Loop indices       */
     register int s1_limit;   /* Search limit in s1 */
     register int s2_length;  /* Length of s2       */

     s2_length = strlen (s2);                /* Minimize function calls.       */
     s1_limit = strlen (s1) - s2_length;     /* If it ain't in here, it ain't. */

     for (i = 0; i <= s1_limit; i++)         /* Search s1 until not enough  */
     {                                       /* characters left to hold s2. */
	  for (j = 0; j < s2_length; j++)
	  {
	       if (s1[i + j] != s2[j])       /* Mismatch? */
	       {
		    if (j > 0)               /* Yes, move i to start of mis- */
			 i += (j - 1);       /* match (but don't back up)    */
		    break;                   /* and start again.             */
	       } /* end if */

	  } /* end for */

	  if (j >= s2_length)                /* All matched?       */
	       break;                        /* Yes, quit looking. */

     } /* end for */

     if (i > s1_limit)                       /* Found s2? */
	  return (-1);                       /* No, return -1 */
     else
	  return (i);                        /* Yes, return position */

} /* end Strloc() */

-- 
The Polymath (aka: Jerry Hollombe, M.A., CDP, aka: hollombe@ttidca.tti.com)
Head Robot Wrangler at Citicorp                   Turn the rascals out!
3100 Ocean Park Blvd.   (213) 450-9111, x2483     No incumbents in '92!
Santa Monica, CA  90405 {rutgers|pyramid|philabs|psivax}!ttidca!hollombe