String compare and copy

Character Strings example from a Well House Consultants training course
More on Character Strings [link]

This example is described in the following article(s):
• Strings in C - strncmp strncpy and friends - [link]

Source code: s1.c Module: C206

/* Strings in C are pointers to arrays of characters, null (\0) terminated.
Which means that if you compare them with the == operator, you're going to be
comparing addresses, and not whether the strings contain the same text. And even
if you put a "*" in front of the variable you're comparing, all you'll do is compare
the first character.

Solution is to use standard functions such as strcmp and strcpy - string compare and
string copy. Both of these are regarded as dangerous as they can run off the end of
stings that aren't properly null terminated, so you also have strncmp and strncpy
which are better regarded, and have an extra parameter which is the maximum number of
characters to compare / copy.

Similarly, fgets to read in a string (use stdin for the keyboard) with a maximum length
is much safer that gets which can easiiy be overrun by a too-long input! */

#include <stdio.h>
#include <strings.h>

int main() {
        char saying[81];
        char host[81];
        int i;

        for (i=0; i<2; i++) {
                printf("Whats yaname: ");
                fgets(saying,80,stdin);

                /* add a "null" in the last place to replace the new line that
                fgets adds (well - the user adds to indicate his response is complete! ) */

                saying[strlen(saying)-1] = '\0';

                printf("You said %s to me\n",saying);

                if (! strncmp(saying,"Graham",80)) {
                        printf("It's your party\n");
                } else {
                        printf("Don't forget the booze\n");
                }
                if (i == 0) strncpy(host,saying,80);
        }
        printf("Party %s and %s\n",host,saying);
}

/* Sample Output

WomanWithCat:harwell grahamellis$ ./s1
Whats yaname: Graham
You said Graham to me
It's your party
Whats yaname: Robert
You said Robert to me
Don't forget the booze
Party Graham and Robert
WomanWithCat:harwell grahamellis$

*/

Learn about this subject

This module and example are covered on the following public courses:
* Learning to Program in C
* Learning to program in C and C++
* Programming in C
* C and C++ Programming
* Learning to program in C and C++
* C and C++ Programming
Also available on on site courses for larger groups

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This example comes from our "Character Strings" training module. You'll find a description of the topic and some other closely related examples on the "Character Strings" module index page.

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