getpgrp() question!

fanyunfei

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

static void ErrMsg(const char *pErr);

int main(void)
{
    pid_t parentProcessID, parentProcessGroupID, childProcessID, childProcessGroupID;

    parentProcessID = getpid();                     /* get parent process ID */

    parentProcessGroupID = getpgrp();               /* get parent process group ID */

    if ((childProcessID = fork()) == -1)            /* create child process */
    {
        ErrMsg("fork() error.";
    }
    else if (childProcessID == 0)
    {
        childProcessGroupID = getpgrp();             /* get child process group ID */
        
        exit(0);
    }

    if (waitpid(childProcessID, NULL, 0) == -1)      /* get child process terminate status */
    {
        ErrMsg("waitpid() error.";
    }

    printf("parentProcessID = %d\n", parentProcessID);
    printf("parentProcessGroupID = %d\n", parentProcessGroupID);
    printf("childProcessID = %d\n", childProcessID);
    printf("childProcessGroupID = %d\n", childProcessGroupID);

    exit(0);
}

static void ErrMsg(const char *pErr)
{
    assert(pErr != NULL);

    printf("%s\n", pErr);

    exit(1);
}

why? output: childProcessGroupID = 0

output result:

[root@localhost root]# ./a.out
parentProcessID = 2781
parentProcessGroupID = 2781
childProcessID = 2782
childProcessGroupID = 0





   


















   

yg

不同的进程，有各自的地址空间，要知道子进程中变量的内容，就要在子进程中输出

fanyunfei

thank you, thank you