Redirect Output Multi-Process

Hi,

I'm trying to compile the following code:

/************** Begin <test.c> ***************/

/*

• Compiled with: gcc -Wall -o test test.c
  */

#include <stdio.h>
#include <unistd.h>

int main(void)
{
printf("I'm process %d, son of %d \n", getpid(), getppid());
printf("Hello \n");
fork();
printf("Everyone \n");
printf("I'm process %d, son of %d \n", getpid(), getppid());
return(0);
}

/************** End <test.c> ***************/

I compile it like:
$ gcc -Wall -o test test.c

Then, if i test it leaving the output to standard output i have:
$ ./test
I'm process 1568, son of 1541
Hello
Everyone
I'm process 1568, son of 1541
Everyone
I'm process 1569, son of 1

If i redirect the output to a file i have:
$ ./test > file.txt
$ cat file.txt
I'm process 1571, son of 1541
Hello
Everyone
I'm process 1572, son of 1571
I'm process 1571, son of 1541
Hello
Everyone
I'm process 1571, son of 1541

My question is if it should happen like this.
How can i redirect the output to a file and have the same as if i
leave it to standard output.
Why is the son process executing the print before the fork? Is it buffered text?
Would like your help on this subject.

Best regards,
Jo�o Jos�

Hi,

You are right, this is due to buffering.
Add flush(stdout) before fork() to see the same results.

Also consider parent PID is 1.
Add sleep(1) before 'return' to see the true PPID.

Regards.

Thnks

flush() doesn't seem to work, can't find that function.
But fflush() works! Did u ment fflush?

Thnks again

Right, fflush().