Printf() not executing before the "while(1)" loop in C language in Linux

Question

I noticed something strange with the following code.

int main()
{
     printf("Test");      // Section 1 do something here....

     while(1)
     {
           ;
     }
}

Section 1 should be executed first, then the program should get stuck in while loop. But the result was that "Test" didn't get printed, but it got stuck in the while loop. I wonder why the code in Section 1 does not get executed?

I ran the code on Ubuntu 14.04 LTS(compiled with the default gcc compiler)

`printf` is buffered. Add a `\n` to the end to flush the buffered output. That or call `fflush(stdout);` before the loop. If it still doesn't print, we'll re-discuss if GCC produces incorrect code :) — StoryTeller - Unslander Monica, Mar 07 '17 at 13:42
So many duplicates - why can nobody search? And, who in the world upvotes this? — KevinDTimm, Mar 07 '17 at 13:52

score 2 · Answer 1 · edited May 23 '17 at 12:32

2

The stdout stream is buffered, therefore it will only display what's in the buffer after it reaches a newline. Add :

fflush(stdout);

after line :

printf("Test");

See also this link for other alternatives.

edited May 23 '17 at 12:32

Community

1
1

answered Mar 07 '17 at 13:43

Marievi

4,951
1
16
33

Please refrain from answering duplicates of duplicates of ... close-vote/flag instead. – too honest for this site Mar 07 '17 at 13:52

score 0 · Answer 2 · answered Mar 07 '17 at 13:54

0

This must work:

#include <stdio.h>

int main() {
    printf("Test");
    while(1){}
}

To compile:

 gcc file.c

To execute:

./a.out

answered Mar 07 '17 at 13:54

Sergio

844
2
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Printf() not executing before the "while(1)" loop in C language in Linux

2 Answers2