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#define _GNU_SOURCE
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <sys/wait.h>

int main(int argc, char *argv[]) {
    int fd;
    const char *tty_path;
    const char *tty_path_env;
    pid_t pid;

    fprintf(stderr, "%i\n", argc);
    tty_path_env = getenv("TAKETTY_PTY");
    if (argc <= 1 || (!strcmp(argv[1], "-") && !tty_path_env)) {
        fprintf(stderr, "Usage: %s (PATH|-)\n", argv[0]);
        fprintf(stderr, "Or set TAKETTY_PTY environment variable\n");
        exit(1);
    }

    tty_path = argv[1];
    if (!strcmp(argv[1], "-")) {
        tty_path = tty_path_env;
    }

    pid = fork();
    if (pid < 0) {
        perror("fork");
        exit(1);
    }

    if (pid > 0) {
        int status;
        waitpid(pid, &status, 0);
        exit(WIFEXITED(status) ? WEXITSTATUS(status) : 1);
    }

    if (setsid() < 0) {
        perror("setsid");
        exit(1);
    }

    fd = open(tty_path, O_RDWR);
    if (fd < 0) {
        perror("open tty");
        exit(1);
    }

    if (ioctl(fd, TIOCSCTTY, 0) < 0) {
        perror("ioctl TIOCSCTTY");
        exit(1);
    }

    if (dup2(fd, STDIN_FILENO) < 0 ||
        dup2(fd, STDOUT_FILENO) < 0 ||
        dup2(fd, STDERR_FILENO) < 0) {
        perror("dup2");
        exit(1);
    }

    if (fd > STDERR_FILENO) {
        close(fd);
    }

    if (argc > 2) {
        execvp(argv[2], &argv[2]);
        perror("execvp");
        exit(1);
    }

    return 0;
}