How does a zombie process manifest itself?

kill -s SIGCHLD

The above is the code for killing any zombie process, But my question is:

Is there an开发者_运维知识库y way by which a Zombie process manifest itself??

steenhulthin is correct, but until it's moved someone may as well answer it here. A zombie process exists between the time that a child process terminates and the time that the parent calls one of the wait() functions to get its exit status.

A simple example:

/* Simple example that creates a zombie process. */

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

int main(void)
{
    pid_t cpid;
    char s[4];
    int status;

    cpid = fork();

    if (cpid == -1) {
        puts("Whoops, no child process, bye.");
        return 1;
    }

    if (cpid == 0) {
        puts("Child process says 'goodbye cruel world.'");
        return 0;
    }

    puts("Parent process now cruelly lets its child exist as\n"
         "a zombie until the user presses enter.\n"
         "Run 'ps aux | grep mkzombie' in another window to\n"
         "see the zombie.");

    fgets(s, sizeof(s), stdin);
    wait(&status);
    return 0;
}