C scanf stop in while

Question

What do I need to correct in the code so that the loop will stop when the user stops entering data?

while(scanf("%i", &num)){   
    printf ("%#o %d 0x%X\n", num, num, num);<br/>
}

It looks like that your code is already doing what you're asking. — user202729, Mar 10 '18 at 15:49
[Does this question help you?](https://stackoverflow.com/questions/28216437/end-of-file-in-stdin) — user202729, Mar 10 '18 at 15:55
@user202729 — doesn’t look like that to me. If it gets EOF, it goes into a tail spin. — Jonathan Leffler, Mar 10 '18 at 16:04
@JonathanLeffler Whoops... /// [What `scanf` function in C returns](https://stackoverflow.com/questions/10469643/what-scanf-function-in-c-returns). — user202729, Mar 10 '18 at 16:07

score 0 · Answer 1 · edited Mar 10 '18 at 16:54

0

Your scanf("%i", &num) only returns when the user presses return/enter, if they've previously typed some non-whitespace characters into the terminal. If the user presses return on an empty line, the function will continue to wait for a non-whitespace characters.

If you type a non-numeric value, before you press return, you'll exit the while loop.

edited Mar 10 '18 at 16:54

J...S

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answered Mar 10 '18 at 16:09

Rich

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score 0 · Accepted Answer · answered Mar 10 '18 at 16:09

You can use this one

#include<stdio.h>
int main(){
    int num;
    printf("Enter -1 for termination:");
while(scanf("%i", &num)>0 ){
        if(num<0)
        break;
  printf ("%#o %d 0x%X\n", num, num, num);

}

return 0;
}

If you type -1 or any character then termination will occur:

Enter -1 for termination:3
03 3 0x3
6
06 6 0x6
9
011 9 0x9
k

Process returned 0 (0x0)   execution time : 8.779 s
Press any key to continue.

C scanf stop in while

2 Answers2