Create multiple sub-processes of Linux

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

int main()
{
    pid_t pid;
    printf("xxxxxxxx\n");
    
    pid = fork();
    if(-1 == pid)
    {
        perror("fork error:");
        exit(1);    
    }
    else if(pid == 0)
    {
        printf("I'm child,pid = %u,ppid = %u\n",getpid(),getppid());
    }
    else
    {
        printf("I'm parent,pid = %u, ppid = %u\n",getpid(),getppid());
        sleep(1);
    }
    printf("YYYYYYYYYYY\n");
    return 0;
}

operation result:

ubuntu1604@ubuntu:~/wangqinghe/C/20190805$ ./fork_test

xxxxxxxx

I'm parent,pid = 2610, ppid = 2558

I'm child,pid = 2611,ppid = 2610

YYYYYYYYYYY

YYYYYYYYYYY

 

Loop to create N sub-processes:

Create five child process using a for loop:

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

int main()
{
    int i;
    pid_t pid;
    printf("xxxxxxxx\n");
    
    for(i = 0; i < 5; i++)
    {
        pid = fork();
        if(-1 == pid)
        {
            perror("fork error:");
            exit(1);    
        }
        else if(pid == 0)
        {
            printf("I'm child,pid = %u,ppid = %u\n",getpid(),getppid());
        }
        else
        {
            printf("I'm parent,pid = %u, ppid = %u\n",getpid(),getppid());
            sleep(1);
        }
    }
    printf("YYYYYYYYYYY\n");
    return 0;
}

After running the program has created a sub-process 2 ^ 5-1.

problem analysis:

problem solved:

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

int main()
{
    int i;
    pid_t pid;
    printf("xxxxxxxx\n");
    
    for(i = 0; i < 5; i++)
    {
        pid = fork();
        if(pid == 0)
        {
            break;
        }
    }

    if(i < 5)
    {
        sleep(i);
        printf("I'm %d child,pid = %u\n",i+1,getpid());

    }
    else
    {
        sleep(i);
        printf("I'm parent\n");

    }
    return 0;
}

In a direct break 0 child process pid == out just fine.

 

operation result:

ubuntu1604@ubuntu:~/wangqinghe/C/20190805$ make fork_test

gcc fork_test.c -o fork_test -Wall -g

ubuntu1604@ubuntu:~/wangqinghe/C/20190805$ ./fork_test

xxxxxxxx

I'm 1 child,pid = 3157

I'm 2 child,pid = 3158

I'm 3 child,pid = 3159

I'm 4 child,pid = 3160

I'm 5 child,pid = 3161

I'm parent