include<stdio.h>
#include<sched.h>
#include<stdlib.h>
#include<unistd.h>
#include<sys/types.h>
int fn(void *a)
{
int *p;
printf("Value of a is = %d",*p);
printf("\n");
return 0;
}
int main()
{
int *i,a=125;
pid_t child;
printf("\n This is parent with id : %d",getppid());
i=(int*)malloc(100*sizeof(int))+100;
child=clone(&fn,i,CLONE_PARENT,&a);
printf("\n Got the child id as : %d",child);
return 0;
}

In the above program, In function "fun()" the first printf statement (i.e, printing the value of a) is not printing anything in the screen. If i give the second printf(simply a new line) i'm getting the output.

1. can anyone explain me why?

2. My friends are telling that I should not use "printf", if I create a process by using "clone()". They are telling me to use "write()" instead.
If they are telling the correct answer, also explain me why I should not use printf in clone?

In stdio, output to a terminal is line buffered by default. Characters are saved in a buffer until either a newline is output or input is read from any stream attached to the terminal device. If you want the output to appear immediately and do not want to include a newline, you can call "fflush(stdout)" after the printf() call.

1 members found this post helpful.

Thanks for the post. now i can explain this to my friends.

Hey, Prafu. Hey, Prafu's friends.

printf() calls write(), and is thread safe. Why NOT use printf?

we are just started learning programming... to be honest we don't even know printf() calls write() (sounds weird!!!... but it is true)so, I don't know what to answer... anyway learned that now..