c守护进程

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <syslog.h>

void showProcess(char *title)
{
    printf("%s pid=%d, ppid=%d, getpgid=%d, getpgrp=%d, getsid=%d\n",
            title, getpid(), getppid(), getpgid(getpid()), getpgrp(), getsid(0));
}
void lf_opensyslog()
{
    openlog("myDaemon", LOG_PID, LOG_DAEMON);
}
int main()
{
    int fd0, fd1, fd2;
    //printf("start\n");
    showProcess("start");
    pid_t pid;
    pid=fork();
    if(pid<0) {
        perror("fork");
        return -1;
    }
    if(pid!=0) {
        // parent
        //sleep(1);
        showProcess("fork 1 parent will exit");
        exit(0);
    }
    showProcess("fork 1 end");

    // child
    setsid();
    showProcess("setsid end");
    pid=fork();
    if(pid<0) {
        perror("fork 2");
        return -1;
    }
    if(pid!=0) {
        // parent 2
        showProcess("fork 2 parent will exit");
        exit(0);
    }
    showProcess("fork 2 end");

    chroot("/");

    umask(002);

    close(0);
    close(1);
    close(2);
    fd0=open("/dev/null", O_RDWR);
    fd1=dup(0);
    fd2=dup(0);

    showProcess("daemonized");

    // daemonize over.
    lf_opensyslog();
    syslog(LOG_INFO, "%s\n", "daemonize over");

    // start process
    sleep(10);

    syslog(LOG_INFO, "%s\n", "daemon stop");
    closelog();
    return 0;
}