C Switch default case not triggering

Question

I'm stuck at a pretty awkward thing. Here's the code:

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

void processCommand(){
    char *c = malloc(sizeof(char) * 128);

    scanf("%s", c);

    switch(*c){
    case '!': 
        printf("Action");
        break;
    case '?': 
        printf("Question");
        break;
    default: 
        printf("Unknown Action");
        break;
    }
}

So what I want is, if the first char of my input is something different than ! or ?, it should just say it's an unknown action. So it works for typing other characters, but everytime i type a whitespace / tab / nothing, it doesn't do anything ?

You mean entering some whitespace, then pressing enter? Well, scanf will skip whitespace, so you read nothing in and stay within scanf until you enter some non-whitespace... — Aconcagua, Jul 04 '17 at 09:26
Just a side note: You don't really need `malloc` here, you can simply have: `char c[128];` instead... — Aconcagua, Jul 04 '17 at 09:32

score 1 · Accepted Answer · answered Jul 04 '17 at 09:30

1

As other users pointed out: scanf ignores whitespaces, fgets doesn't.

void processCommand(){
    char *c = malloc(sizeof(char) * 128);
    fgets (c, sizeof(char) * 128, stdin);

    switch(*c){
        case '!': 
            printf("Action");
            break;
        case '?': 
            printf("Question");
            break;
        default: 
            printf("Unknown Action");
            break;
        }
}

answered Jul 04 '17 at 09:30

7hibault

2,371
3
23
33

1

Dont answer a duplicate question – Vishwajeet Vishu Jul 04 '17 at 09:30
@VishwajeetVishu You may be right :) – underscore_d Jul 04 '17 at 09:34
2

@VishwajeetVishu You're right though, I shouldn't have answered it, I'll be more cautious next time and stick to the flag/comments https://meta.stackexchange.com/questions/10841/how-should-duplicate-questions-be-handled – 7hibault Jul 04 '17 at 09:36
@underscore_d see easy 25 reputation :/ – Vishwajeet Vishu Jul 04 '17 at 09:39

C Switch default case not triggering

1 Answers1