Sleep

unsigned int sleep(unsigned int seconds);

sleep() is a system call that can make the process to sleep for a specified period.

/* Wait/sleep.c */
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>


int main(int argc,char *argv[])
{
    printf("Before fork...\n");
    if(fork() == 0)
    {
        printf("Hello World!\n");
        exit(0);
    }
    sleep(1);
    printf("After fork...\n");
    return 0;
}

By using sleep(), parent can put to a suspended state and wait for the child. However, sleep() is not desirable (we need to specify the time...).