C - Comparing string literal with character array

Question

I am new to C and am still a bit confused about how to use strings via character arrays.

In my C program, I am accepting commands from the user:

char command[20];
scanf("%s",command);

Of course, afterwards I want to figure out what command they typed (something similar to: "if (command == "hello"), then do something"). I know this is not possible in C because I am comparing a string literal to a character array, but what would be a good way to it? I have tried using strcmp(command, "hello") and still got errors.

Any advice you can provide would be very appreciated. Thank you!

Solution 1

strcmp returns 0 when the strings are the same. I have code that uses strcmp comparing character arrays to string literals, and I was quite confused when it wasn't working. Turns out it was wrong for me to assume it would return 1 when the string are the same!

Maybe you've made the same mistake?

Solution 2

I have written a complete version of what I think you are trying to do:

    #include <string.h>
    void main()
    {

       char command[20];
       scanf("%s",command);

       // command and "hello" can be less than, equal or greater than!
       // thus, strcmp return 3 possible values
       if (strcmp(command, "hello") == 0)
       {
          printf("\nThe user said hello!");
       }

    }

Several people have commented about using scanf and they are correct, except that a new programmer has to start somewhere in learning this stuff, so don't feel too bad we are all learning...

Hope this helps.

Solution 3

I think this is a perfect starting point for you:

http://www.wikihow.com/Compare-Two-Strings-in-C-Programming

It's probably written at the right level for you. Good luck and welcome to stackoverflow!