pfork.c

// SPDX-License-Identifier: GPL-3.0-or-later
// SPDX-FileCopyrightText: 2020,2024 sulincix <pardusccix@yandex.ru>
// SPDX-FileCopyrightText: 2024-2025 kurth4cker <kurth4cker@gmail.com>

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

mode_t umask_val = 0;
const char *logfile = "pfork.out";
const char *infile = "pfork.in";

bool silent = true;

void set_umask(mode_t value)
{
    umask_val = value;
}

void skeleton_daemon()
{
    pid_t pid;

    /* Fork off the parent process */
    pid = fork();

    /* An error occurred */
    if (pid < 0)
        exit(EXIT_FAILURE);

    /* Success: Let the parent terminate */
    if (pid > 0)
        exit(EXIT_SUCCESS);

    /* On success: The child process becomes session leader */
    if (setsid() < 0)
        exit(EXIT_FAILURE);

    /* Catch, ignore and handle signals */
    // TODO: Implement a working signal handler
    signal(SIGCHLD, SIG_IGN);
    signal(SIGHUP, SIG_IGN);

    /* Fork off for the second time*/
    pid = fork();

    /* An error occurred */
    if (pid < 0)
        exit(EXIT_FAILURE);

    /* Success: Let the parent terminate */
    if (pid > 0) {
        fprintf(stderr, "\nDaemon started:\t[%d]\n",getpid ()+pid);
        exit(EXIT_SUCCESS);
    }
    
   
    /* Set new file permissions */
    umask(umask_val);
    
    if (silent) {
        mode_t mode = S_IRUSR | S_IWUSR | S_IRGRP;
        int fdin = open(infile, O_RDONLY,mode);
        int fdout = open(logfile, O_WRONLY | O_CREAT,mode);
        int fderr = open(logfile, O_WRONLY | O_CREAT,mode);
    
        /* Set in, out and err to file*/
        close(0);
        dup(fdin);
        close(fdin);
        close(1);
        dup(fdout);
        close(2);
        dup(fderr);
        close(fdout);
    } else {
        /* Set in, out and err to pty*/
        int master_fd, slave_fd;

        // Open a pseudo-terminal
        if (openpty(&master_fd, &slave_fd, NULL, NULL, NULL) == -1) {
            perror("openpty");
            exit(EXIT_FAILURE);
        }
        printf("The master psuedo-terminal id is %d\n",master_fd);

        // Replace stdin with the slave side of the PTY
        if (dup2(slave_fd, STDIN_FILENO) == -1) {
            perror("dup2");
            exit(EXIT_FAILURE);
        }

        // Replace stdout with the slave side of the PTY
        if (dup2(slave_fd, STDOUT_FILENO) == -1) {
            perror("dup2");
            exit(EXIT_FAILURE);
        }

        // Replace stderr with the slave side of the PTY
        if (dup2(slave_fd, STDERR_FILENO) == -1) {
            perror("dup2");
            exit(EXIT_FAILURE);
        }

        // Close the unused PTY file descriptor
        close(slave_fd);

    }

}