vfork syscall

bandaru_sivakrishna · 07-11-2009, 09:31 PM

#include<stdio.h>
#include<sys/types.h>
#include<unistd.h>

void main()
{
printf("\nTEST THE FORK SYS CALL\n");
vfork();
vfork();
vfork();
printf("\nhello world\n");
}

Note: the output is "hello world" print only 2 times why?

Valery Reznic · 07-12-2009, 04:52 AM

Quote:

Originally Posted by bandaru_sivakrishna

#include<stdio.h>
#include<sys/types.h>
#include<unistd.h>

void main()
{
printf("\nTEST THE FORK SYS CALL\n");
vfork();
vfork();
vfork();
printf("\nhello world\n");
}

Note: the output is "hello world" print only 2 times why?

Add

Code:

exit(0)

after last printf and it will work as it should be

x_terminat_or_3 · 07-13-2009, 05:11 PM

shouldn't that be

Code:

_exit(0);

when inside a child?

Valery Reznic · 07-13-2009, 11:21 PM

Quote:

Originally Posted by x_terminat_or_3

shouldn't that be

Code:

_exit(0);

when inside a child?

Yes and no.

After reading
http://linux.die.net/man/2/vfork

I realized that code is wrong: after vfork only exec* or _exit() allowed,
i.e behavour for

Code:

vfork()
printf()

is undefined.

So when I added exit() and it's work it was only by chance()