Question

#include <stdio.h>
#include <string.h>

int main(){        
    char *command="0";

    do {   
      printf("[A]dd, [P]rint, [Q]uit\n");
      scanf("%s", command);

    while (strcmp(command, "a") != 0 && strcmp(command, "A") != 0 && strcmp(command, "p") != 0 && strcmp(command, "P") != 0){
        printf("Invalid input. Please enter one of the commands listed above.\n");
        scanf("%s", command);
    }       

       if (strcmp(command, "a") == 0 || strcmp(command, "A") == 0){
           printf("You selected add.\n");
       }
       else if (strcmp(command, "p") == 0 || strcmp(command, "P") == 0){
           printf("You selected print.\n");
       }
    }while (strcmp(command, "q") != 0 && strcmp(command, "Q")!= 0);
    return 0;
}

I want the program to take in a letter from the user from one of the specified commands printed in the beginning. I want the program to exit if they enter q or Q. Took me a while simply to figure out how to do comparisons with strings for the loops and ifs. now when i run the program it crashes though. Looking for insight as to why its crashing.

Answer 1

Yes, make your buffer command into a regular array, and make it larger:

char command[256];

No need to initialize it, scanf will take care of that. Also, it won’t affect the crashing but if you’re only checking one letter, you can do it like this:

if command[0] != 'a' && command[0] != 'A' (etc.)

Note the single quotes: This is a character comparison.