From: Erik Max Francis <max AT alcyone DOT com>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Help with scanf()
Date: Tue, 22 Jul 1997 19:16:29 -0700
Organization: Alcyone Systems
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James MacDonald wrote:

> At the moment I'm using scanf() - I need to read a value from the
> keyboard and compare it with a generated one made by a program.
> 
> Here's the code :
> 
> char * enter;
> 
> scanf("%s", enter);
> printf("Entered string : %s", enter);
> if (enter == chalcrypt) printf("it worked!");
> 
> For entered string, '(null)' is displayed, and that only.
> What am I doing wrong?

You're not making sure your string has enough memory.  In fact, you're not
initializing enter at all, so you've got a dangling pointer, and should be
grateful your program doesn't crash.  (It's luck that it doesn't crash,
and furthermore, that enter just _happened_ to be 0.)

What you need to do is something like this:

    char enter[256]; /* or however much is necessary */
    scanf("%s", enter);
    printf("Entered string: %s\n", enter);

Furthermore, you can't just compare strings with the == operator, because
that's only comparing the addresses of the pointers, which will never
work.  You need to use strcmp:

   if (strcmp(enter, chalcrypt) == 0) printf("It worked!\n");

> Is there an easier way to read the keyboard?
> I've tried gets() but I've got stuck there too :(

For the same reason.  I strongly suggest you use get a good ANSI C book
and read up on arrays, pointers, and strings.

-- 
       Erik Max Francis, &tSftDotIotE / email / max AT alcyone DOT com
                     Alcyone Systems /   web / http://www.alcyone.com/max/
San Jose, California, United States /  icbm / 37 20 07 N  121 53 38 W
                                   \
   "Love is not love which alters / when it alternation finds."
                                 / William Shakespeare, _Sonnets_, 116