C-如何多次使用带有scanf的字符串

Question

Here's my code:

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

int main(void)
{
     char terminal[100];

     printf("Enter cmds: ");
     scanf(" %s", terminal);

     if(strcmp(terminal, "help") == 0){
           printf("test");
           scanf(" %s", terminal); // trying to detect if a user types
                                   // "help" the menu will pop up again
     }

     return 0;
     }

When a user types "help", the menu pops up, (good so far). But when they type "help" again, the menu does not pop up. Does anybody know what is going on?

Answer 1

The initial comments hit the nail on the head here. You need to loop over new input multiple times. This can be done fairly easily.

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

int main(void)
{
    char terminal[100];

    printf("Enter cmds: ");

    // this expression will return zero on invalid input, exiting the loop
    while (scanf("%99s", terminal) == 1) {  
        // your if statement and other code you want to repeat go here.
    }
}

To better encapsulate this kind of behaviour, defining some sort of function that compares strings and returns an element of an enum is a very common practice, but not required in this question.