linux 编写守护进程

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

void daemonize(void)
{
    pid_t pid, sid;

    // Fork off the parent process
    pid = fork();
    if (pid < 0) {
        exit(EXIT_FAILURE);
    }
    // If we got a good PID, then we can exit the parent process.
    if (pid > 0) {
        exit(EXIT_SUCCESS);
    }

    // Create a new SID for the child process
    sid = setsid();
    if (sid < 0) {
        exit(EXIT_FAILURE);
    }

    // Change the current working directory
    if ((chdir("/")) < 0) {
        exit(EXIT_FAILURE);
    }

    // Set file permissions mask
    umask(0);

    // Close out the standard file descriptors
    close(STDIN_FILENO);
    close(STDOUT_FILENO);
    close(STDERR_FILENO);

    // Open file descriptors to /dev/null
    open("/dev/null", O_RDONLY); // STDIN
    open("/dev/null", O_RDWR);   // STDOUT
    open("/dev/null", O_RDWR);   // STDERR
}

int main(void)
{
    daemonize();

    // Daemon code goes here

    while (1) {
        // Perform daemon tasks
        sleep(1);
    }

    return EXIT_SUCCESS;
}