getchar() stopping after printing one value

Question

Function of the code: The function of my code is pretty simple. It converts a phone number with numbers into a phone number.

#include <stdio.h>

main(){

  char num;

  printf("Please enter a phone number with letters to be converted into a phone number: \n");

  while ((num = getchar()) != '\n') {
    switch(num){
      case 'A': case 'B': case 'C': printf("2"); break;
      case 'D': case 'E': case 'F': printf("3"); break;
      case 'G': case 'H': case 'I': printf("4"); break;
      case 'J': case 'K': case 'L': printf("5"); break;
      case 'M': case 'N': case 'O': printf("6"); break;
      case 'P': case 'R': case 'S': printf("7"); break;
      case 'T': case 'U': case 'V': printf("8"); break;
      case 'W': case 'X': case 'Y': printf("9"); break;
      default: putchar(num);
    }

    return 0;

  }

}

The problem is that the getchar() is taking one value and changing that number/letter only when I want it to change the whole thing.

Things I have done: I found someone else code who did this already, copied it, changed it a bit (removed toupper function), stacked the cases side by side and it didn't work for some reason. Is it because of the placement of the switch statement? But I don't think it is because of that because it ends after printing one value.

What I want it to do:

Enter phone number: 1-800-COL-LECT
1-800-265-5328

What it does:

Enter phone number: 1-800-COL-LECT
1
Enter phone number: 5-469-COL-LECT
5

`getchar` does not print anything. And it returns an `int` intentionally, not a `char`. — too honest for this site, Mar 30 '17 at 19:54
`return 0;` What do you think that will do as the last line in the `while` loop? Use a debugger to step through your code line by line. That's the right way to debug such issues and will clearly show you the problem. — kaylum, Mar 30 '17 at 19:54
So do you know any reason why this code isn't working? `getchar()` functions with a `char` type `var`. — Manny, Mar 30 '17 at 19:56
`return 0; }` --> `} return 0;` or delete `return 0;` Also `main()` --> `int main(void)` — BLUEPIXY, Mar 30 '17 at 19:56
You should filter out spaces, newlines and hyphens too. And deal with `'#'` and `'*'`. — Weather Vane, Mar 30 '17 at 19:57
That is the stupidest thing I have ever done. Thanks @kaylum for finding that. Put that as your answer, so I could give it a check mark. — Manny, Mar 30 '17 at 19:58
`getchar()` returns a result of type `int` so the caller can distinguish between `EOF` and any valid character value. You *can* assign the result to a `char`, but then you're discarding important information. And once you fix your code, it's likely to go into an infinite loop if it encounters end-of-file before reading a `'\n'` character. Also, `main()` should be `int main(void)`. — Keith Thompson, Mar 30 '17 at 19:58
Isn't that clear that the real prolem was the `return 0;` in the `while` loop. — Roy Avidan, Mar 30 '17 at 20:10
@רועיאבידן: That was the cause of the symptom the OP was asking about, but it's not the only problem in the code. — Keith Thompson, Mar 30 '17 at 22:03

score 0 · Accepted Answer · answered Mar 30 '17 at 21:04

The problem in the code is that return 0; is inside of your while loop. What you need to do is move the return 0; outside of the loop and it will fix it.

#include <stdio.h>

main(){

  char num;

  printf("Please enter a phone number with letters to be converted into a phone number: \n");

  while ((num = getchar()) != '\n') {
    switch(num){
      case 'A': case 'B': case 'C': printf("2"); break;
      case 'D': case 'E': case 'F': printf("3"); break;
      case 'G': case 'H': case 'I': printf("4"); break;
      case 'J': case 'K': case 'L': printf("5"); break;
      case 'M': case 'N': case 'O': printf("6"); break;
      case 'P': case 'R': case 'S': printf("7"); break;
      case 'T': case 'U': case 'V': printf("8"); break;
      case 'W': case 'X': case 'Y': printf("9"); break;
      default: putchar(num);
    }
  }
  return 0;
}

Originally founded by @kaylum

This fixes the problem the OP asked about, but it leaves several other problems in place. See my first comment on the question. — Keith Thompson, Mar 30 '17 at 22:06

getchar() stopping after printing one value

1 Answers1