Thread: using sscanf to skip trailing whitespace

Code:

#include <stdio.h>
#include <stdlib.h>

int main(int argc, char *argv[])
{
    char line[1024] = { 0 }; 
    char extra[256] = { 0 };
    char path[256] = { 0 };

    printf("enter dir name: ");
    fgets(line, 1024, stdin);
    
    strncpy( path, line, 255 );             // Copy maximum of 255 characters from line to path
    path[ strlen( path ) - 1 ] = '\0';      // Replace newline character with NULL character
                                            // I am unsure if the above line of code is very good practice, even though it works.
    
    printf("%s\n\n", path );
    
    return 0;
}

The above will work, though as I mentioned in the comments, I don't know what our strict brothers here will think about my newline hack.


[EDIT]
Holy crap, I missed one big error you made. Your call to fgets is allowing 1024 bytes to be read into a buffer (line[]) which is only 256 bytes - BAD! If the user enters more than 256 characters, you enter undefined land - you don't want to go there. :P

>I don't know what our strict brothers here will think about my newline hack.
It assumes that a newline is present. If you do a forum search, you'll probably find a thread where we tossed around lots of ideas for this. Though the generally accepted solution is:

Code:

char *newline = strchr ( array, '\n' );

if ( newline != NULL )
  *newline = '\0';

>If the user enters more than 256 characters, you enter undefined land - you don't want to go there. :P
And you can avoid it by using sizeof rather than a magic number:

Code:

fgets ( array, sizeof array, stdin );

Though this assumes the array is actually an array. If it's a pointer to dynamically allocated memory or the argument to a function, sizeof won't work directly.

Yes, I knew that making an assumption was going to be an issue. And the solution seems good, something I'd probably end up with if I was told to make no assumptions.

As for the magic number, I understand the reasoning there and fair enough too. But a method Salem often uses as an example is:

Code:

char buf[BUFSIZ];

fgets( buf, BUFSIZ, stdin );

Is that not the same thing?

They both have "problems":

The "sizeof object" method only works if the array is defined in scope, and not passed as an argument.
The defined object method works until you later decide you don't want BUFSIZ any more, and want ... whatever ... then you have to go search and replace.

They both work, if you use them correctly. Funny how that is.


Quzah.

>Is that not the same thing?
Well, it's still a bit of an issue because you can't redefine a standard macro, and it can turn into a big problem if you try to use a different array with a different size and forget to update the size parameter.

Ahh ok, so they are only a problem if you don't keep track of what you're doing. But in a technical sense, there really isn't a better way to do the job. I think I've got it now. :P