strcmp problem

[TheObserver]

I am doing a strcmp on a filename returned from a directory pointer. However, the comparisons don't seem to work, and the program flows straight through (and thus all of the logic evaluates to "true&quot until it hits the exit(1) in the code below. Any ideas on why the logic isn't working right?

while ( (direntp = readdir( dirp )) != NULL )
{
printf("\n\nhello\n\n\n"
if ( strcmp ( direntp->d_name, "." ) == 0 ||
strcmp ( direntp->d_name, ".." ) == 0 )
{
if(consoleout)
{
printf("Invalid input file.\n"
}
}
// if((strcmp(direntp->d_name, ".&quot != 0) && (strcmp(direntp->d_name, "..&quot != 0))
else
{
printf("\n\nframe file: %s\n",direntp->d_name);
printf("strcmp %i\n",strcmp(direntp->d_name,".&quot);
printf("strcmp %i\n",strcmp(direntp->d_name,"..&quot);

//test our first argument and see what it is.
if ((ffptr = fopen( direntp->d_name, "r" )) == NULL)
{
if(consoleout)
{
printf("\nError opening input frame file: %s\n",direntp->d_name);
}
exit(1);
}

//do stuff

}



I get the following output to my console:
______
% ./test /home/


hello




frame file: .
strcmp -55
strcmp -68

Error opening input frame file: .
______

Thanks for your time.

 

[guestgulkan]

strcmp will fail if one string is longer than the other being compared.
So comparing "." against an entire directory string such as "./thisdir/thisfile.ext" will fail even though the second string starts with a dot.

 

[JasonDeckard]

If you do want to compare the first n characters of two strings, consider using strncpy():

int strncpy( const char *s1, const char *s2, size_t n );

 

[Kocky]

You write:
"if ( strcmp ( direntp->d_name, "." ) == 0 "

As I understand "direntp->d_name" is a structure type.
You can not use strcmp on a structure type because it only contains addresses. So your comparing a addres with a dot.

You have to use memcmp for this. Your code would be like:

"if (memcmp(direntp->d_name, ".", sizeof(direntp->d_name)) == 0)

 

[marsd]

Kocky,
You are incorrect.
If you would take a look at the definition for
the direntp structure and the readdir function def
you will see that this is a pointer to a character
array and is perfectly legal.

 

[butthead]

if ( strcmp ( direntp->d_name, "." ) == 0 ||
strcmp ( direntp->d_name, ".." ) == 0 )


try changing the above to

if (( strcmp ( direntp->d_name, "." ) == 0) ||
(strcmp ( direntp->d_name, ".." ) == 0) )

or

if (!strcmp ( direntp->d_name, ".&quot ||
!strcmp ( direntp->d_name, ".." ) )

maybe yes, maybe no

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