Thread: How do I or is it possible to compare a structure member to a string?

Hi - with a specific question, I'd like to know if it is possible (I assume it is) to copy out a structures member to a variable and compare it to something else.

For example I have the following structure:

Code:

struct cmd_s {
char cmd[5];
char filename[256];
}

Once it is filled in I can see that the values are getting sent over my socket correctly, however I want to use an if statement to control my program flow.

Code:

	struct cmd_s *cmdrecieved;
	char bufferd[BUFFER_SIZE];
	
	recvfrom(fd, bufferd, BUFFER_SIZE, 0, (struct sockaddr *)&srcaddr, (socklen_t*)&srcaddrSize );
	
	cmdrecieved = (struct cmd_s *)bufferd;
	printf( " before cmd = %s \n", cmdrecieved->cmd);  // This works
	
       //This is what I would like it to do
	if (strcmp(cmdrecieved->cmd,"send"))  {
	         printf( " awesome = %s \n", cmdrecieved->cmd);
	} else
	{
	  printf("she broken");
	}

You can see the above code is wrong, but it should illustrate what I was trying to do.

Any suggestions?

it doesn't work.... other ideas?

Originally Posted by lantzvillian

it doesn't work.... other ideas?

So you changed the if statement for the strncmp that NeonBlack pointed out?
And your printf prints :
before cmd = send


Dylan

yes the if statement prints out " cmd = send " and it prints out "shes broken"

Not sure what to tell you, it should work after you fixed the strncmp if statement.

Maybe post your new code with the fix.

Dylan

Look even something like this doesn't work:


If I entered # ./program filename get

Code:

if (strncmp(argv[2],"get",3) = 0 ) {

 printf("this worked");

}

I don't get why a comparison of this nature wouldn't work....

Originally Posted by lantzvillian

I don't get why a comparison of this nature wouldn't work....

Because it's wrong

Code:

if (strncmp(argv[2],"get",3) == 0 ) {

Dylan

The strncmp only compares n chars, so your sample program would also match on
./program filename getting.
see strncmp

You can send me a private message if you want.

Dylan

Ahh sweet deal. I'd PM you if I could.. I keep getting permission errors when I click anyone's profile.

Well it did compile on Fedora 13 x64 with gcc 4.3x something. There were no errors, just that the comparison was not working at all. If I had an error I would have posted it.

I can PM now, thanks.

And I do use my information mother named Google. However, I find that alot of Cs documentation and API is less centralized in comparison to say Java's or PHP's or Drupal's.