如何以一种不需要收割孩子的方式进行分叉过程

Question

I seem to have a vague memory that some facility in Linux exists that allows one to fork() a process in such a way that the child is automatically reaped by the system without a zombie being created. What is this mechanism? Or is my memory just wrong?

Answer 1

The portable way to do this is to double-fork:

pid = fork();
if (pid>0) {
    int status;
    while (waitpid(pid, &status, 0) && !WIFEXITED(status) && !WIFSIGNALED(status));
    if (WIFSIGNALED(status) || WEXITSTATUS(status)) goto error;
} else if (!pid) {
    pid = fork();
    if (pid) _exit(pid<0);
    else {
        // do child work here
        _exit(0);
    }
} else goto error;

Answer 2

我在考虑Glib的g_spawn_ *方法，除非你指定你不想要那个默认行为，否则它会自动收割孩子。

Answer 3

You can ignore SIGCHLD so it's doesn't create zombie ;)

signal(SIGCHLD, SIG_IGN);

doc here: http://man7.org/linux/man-pages/man2/sigaction.2.html

Answer 4

This can also be done via prctl()

prctl(PR_SET_PDEATHSIG, SIGTERM);

The above line inserted in the child process can cause it's termination when the parent process is dead. This can also work when any sub-reapers die(after they parent the child process), and if you need it's actual parent's death to kill the child process, then store the parent's pid before fork() and check it in the child process.

if (getppid() != parent_pid_before_fork) exit(1);