CODEWITHSUNDEEP
clinuxforkwait
maziar parsaeian
maziar parsaeian

Reputation: 51

fork() two child process in c

a c program that forks 2 child,first one sleeps for 10 sec,the second one waits for the exit of the first child and prints a related message,the parent waits for the termination of the 2 child,i do not know why the second child does not wait for the 1st child termination.plz help

#include <sys/types.h>
#include <sys/wait.h>
#include <stdio.h>
#include <signal.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>

main(){
    int status;
        pid_t child1, child2,ret,ret2;

    child1=fork();
    if(child1==0){
        //this branch of code is being executed by the child1 process

        printf("I'm the first child with %d, I sleep for 10 sec \n",getpid());
        sleep(10);
        printf("child1 pid %d exiting\n",getpid());
                exit(1);
    }
    if(child1>0){

        child2=fork();
        ret=waitpid(child1,&status,0);


        if(child2==0){

             wait(&status);//???why child2 does not wait the child1 exit?

            printf("I'm the second child with %d, I have waited for the termination of the first child\n",getpid());
                        printf("child2 exited\n");
                        exit(1);

        }
        if(child2>0){


                        printf("father of child2 is waiting\n");
            ret2=waitpid(child2,&status,0);
            printf("I'm the father, my terminated process id is: %d \n",getpid());
            printf("I'm the father, my first child's id is: %d\n", child1);
            printf("I'm tha father, my second child's id is: %d\n", child2);

        }


    }

return 0;
}

Upvotes: 0

Views: 7175

Answers (3)

a.m.
a.m.

Reputation: 2161

In process hierarchy children doesn't wait neither for parent nor for another children. You can use some form of IPC mechanism to communicate the info from 1 child to another,

Upvotes: 0

NPE
NPE

Reputation: 500167

The wait family of functions can only be used by parent to wait for a child. They can't be used by a process to wait for a sibling.

Upvotes: 4

zwol
zwol

Reputation: 140445

A process can only wait for its immediate children. In this case, that means the parent process has to do the wait for both child1 and child2.

Upvotes: 3

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