Help returning strings

hi

the strings you are using will be written to the stack when the function is called
then when the function returns the pointer on conpletion. That pointer will be undefined.

your probally just using those literal strings to devolop your program

you could use a string in the calling function, which would be valid
and pass a pointer to that.

Thank you for your input!

Here's the strFileExt(...); function I made that generates an error:

char * strFileExt(char filename[])
{
      /// Variables
      // Extension:
      char extension[1024];
      // Loop:
      int x;
      
      // Get the extension:
      snprintf(extension, sizeof(extension), "");
      for(x=0;x<strlen(filename);x++)
      {
            if(filename[x] == '.')
            {
                  snprintf(extension, sizeof(extension), "");
            } else {
                  snprintf(extension, sizeof(extension), "%s%c", extension, filename[x]);
            }
      }
      
      // Return the extension
      return extension;
}

Hope this helps,


Jonny

Or, if you are happy with the function acting a little oddly sometimes (like strtok), you could use:

static     char extension[1024];

This will force only one occurrence of 'extension' to appear in memoery but it will not change without further calls to it. The problem is that each call overwrites the results of the last call.

Oaul

Thanks to the comment posted by ikework on 11/20/2005 03:08PM GMT+00:00, a warning has dissappeared. I am very greatful for the function you have posted, and I hope to use this as an example to fix the rest.

Thanks,


Jonny
PS: Enjoy your points!

Well, you appear to have solved my problem. Thanks a lot! :-D

[jonnyk@bsdbox]~/jhttp/0.01-BETA1: $ ./compile.sh
Building 0.01-BETA1 build 169
   * jhttp binary
   * jhttp-fireup
[jonnyk@bsdbox]~/jhttp/0.01-BETA1: $

:D

Thanks!


Jonny

jonny,

Please be aware that the strFileExt implementation Ike has given you has problems. Please be careful with it.

Ike,

This sounds like I am having a go! I am not at all!!! There's a couple of big problems with the code.

1. snprintf(extension, sizeof(extension), ""); is a VERY inefficient way to empty a string, although I am glad to see some effort made to use the 'sn...f' functions for extra security and buffer-overflow checks.

2. You can have '.'s in the file name! Its only the last '.' that is the extension. I use:
char * extension = strrchr(name, '.');

Making the full code look like:

char * strFileExt(char filename[], char extension[] )
{
    char * ext =  = strrchr(filename, '.');
    if ( ext != NULL )
    {
     strncpy(extension,ext,sizeof(extension));
    }
    else
    {
     strcpy(extension,"");
    }
     // Return the extension
    return extension;
}

Paul

Paul,

Thank you for supplying this information, it appears to be very useful to the kind of application I am building.

1: The method you have supplied in your code is useful, I will be using strcpy(); clear string from now onwards.
2: I was not aware of this simple way to find the extension, I will attempt to use it in future.

If there was still points available, I would mark you as an assisted answer, but sadly, there isn't.

Thanks anyway,


Jonny

ya paul, thanks, you are absolutely right. my aim was to show jonny the case, where the problem is. to demonstrate it
i adapted his code and changed only the things, that i thought were important to make clear, where the problem is.
you are right, at least i had should point out, that there are more problems in this code, but i didn't want to *overload*
jonny with that info or changes made to his code, probably that was a mistake ...

i'm still learning too ;-)

ike

Ike,

>>my aim was to show jonny
I could see that, and you did a good job.

Jonny,

Dont worry about the points.

>>2: I was not aware of this simple way to find the extension, I will attempt to use it in future.
Well, actually, its not infallible. Here's an example you probably should deal with for a correct algorithm:

C:\Hello.There.Paul\No-Extension-File

Paul