linux下编写守护进程

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

void daemonize() {
    pid_t pid;

    // Step 1: Fork off the parent process
    pid = fork();
    if (pid < 0) {
        exit(EXIT_FAILURE);
    }
    if (pid > 0) {
        exit(EXIT_SUCCESS);
    }

    // Step 2: Create a new session and set the process group ID
    if (setsid() < 0) {
        exit(EXIT_FAILURE);
    }

    // Step 3: Set file permission mask
    umask(0);

    // Step 4: Change the current working directory
    if (chdir("/") < 0) {
        exit(EXIT_FAILURE);
    }

    // Step 5: Close unnecessary file descriptors
    close(STDIN_FILENO);
    close(STDOUT_FILENO);
    close(STDERR_FILENO);

    // Open log file
    openlog("mydaemon", LOG_PID, LOG_DAEMON);

    // Step 6: Handle signals (optional)
    signal(SIGTERM, sigterm_handler);
}

void sigterm_handler(int signum) {
    syslog(LOG_NOTICE, "Received SIGTERM, exiting...");
    closelog();
    exit(EXIT_SUCCESS);
}

int main() {
    daemonize();

    // Step 8: Execute the daemon's core task
    while (1) {
        syslog(LOG_INFO, "Daemon is running...");
        sleep(60); // Sleep for 60 seconds
    }

    closelog();
    return EXIT_SUCCESS;
}