Question

#define MAX_COMMAND_LEN 32

char command[MAX_COMMAND_LEN];
while (1) {
    if (fgets(command, MAX_COMMAND_LEN, stdin) == NULL) {
        perror("Error: standard function fgets has failed\n");
        break;
    }

    if (command[strlen(command) -1] != '\n') {
        printf("Error: command length must be less than or equal to 30 characters\n");
        continue;
    }
    else {
         printf("Error: command not found\n");
    }

}
quit();

I have couple of problems which I’m not able to handle:

1. When I press Enter, it stops the loop and doesn’t print the command not found message.
2. When I enter a command with a size bigger than 30 characters it prints both the command not found and the command length must be less than or equal to 30 characters messages.
3. When I enter a 64 size command it prints twice the 30-length message.

I believe it divides the input to 30-length segments and input each one of them, how do I overcome it? I tried to flush stdin, it does not work. I want to get rid of the rest of the input. How do I overcome all these problems?

Answer 1

For your second problem, it’s because fgets fetches the 31 (MAX_COMMAND_LEN, minus space for the terminating '\0' character) first characters, you notice it’s no newline and the next time around the loop fgets fetches the remaining characters.