linux 守护进程实现

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

void daemonize() {
    pid_t pid;

    // Fork off the parent process
    pid = fork();
    if (pid < 0) {
        exit(EXIT_FAILURE);
    }
    if (pid > 0) {
        exit(EXIT_SUCCESS); // Parent process exits
    }

    // Create a new session and set the process group ID
    if (setsid() < 0) {
        exit(EXIT_FAILURE);
    }

    // Set new file permissions
    umask(0);

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

    // Close 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() {
    daemonize();

    // Main loop of the daemon
    while (1) {
        // Perform daemon tasks here
        sleep(1);
    }

    return 0;
}