Path: utzoo!utgpu!news-server.csri.toronto.edu!clyde.concordia.ca!ccu.umanitoba.ca!mills
From: mills@ccu.umanitoba.ca (Gary Mills)
Newsgroups: comp.lang.c
Subject: Re: NULL pointer problem on SUN
Message-ID: <1990Nov10.230033.1502@ccu.umanitoba.ca>
Date: 10 Nov 90 23:00:33 GMT
References: <1255@digi.lonestar.org>
Organization: University of Manitoba, Winnipeg, Canada
Lines: 27

In <1255@digi.lonestar.org> theruska@digi.lonestar.org (Thomas Heruska) writes:

>I believe that the problem occurs due to the fact strtok returns a NULL 
>pointer when it encounters the end of the string it is parsing.  I am trying
>to copy this NULL pointer to another string and check that string for the NULL.

You have a serious misconception about NULL.  A NULL pointer does not point to
a null character.  In fact, a NULL pointer does not point at all.  Neither is
a NULL pointer the same as a null string.  When you have a pointer that you
suspect may be NULL, you must test the pointer before referring to the object
at which the pointer points.  This way should work on all the machines:

   char token[50];
   char mesg[50];
   char *ptr;

   strcpy(mesg," \0");

   ptr = strtok(mesg," \0");
   if ( ptr != NULL ) {
       strcpy(token, ptr);
       . 
       .
       .

-- 
-Gary Mills-         -Networking Group-          -U of M Computer Services-