fork2.c

来自「UNIX编程高级环境（第二版）的进程部分的程序源码」· C语言 代码 · 共 36 行

#include    <sys/types.h>
#include    <sys/wait.h>
#include    "ourhdr.h"

int
main(void)
{
    pid_t    pid;

    if ( (pid = fork()) < 0)
        err_sys("fork error");
    else if (pid == 0) {        /* first child */
        if ( (pid = fork()) < 0)
            err_sys("fork error");
        else if (pid > 0)
            exit(0);    /* parent from second fork == first child */

        /* We're the second child; our parent becomes init as soon
           as our real parent calls exit() in the statement above.
           Here's where we'd continue executing, knowing that when
           we're done, init will reap our status. */

        sleep(2);
        printf("second child, parent pid = %d\n", getppid());
        exit(0);
    }

    if (waitpid(pid, NULL, 0) != pid)    /* wait for first child */
        err_sys("waitpid error");

    /* We're the parent (the original process); we continue executing,
       knowing that we're not the parent of the second child. */

    exit(0);
}