#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <sys/ioctl.h>
#include <termios.h>
#include <signal.h>

void die(const char *ptr, ...)
{
        va_list vlist;
        va_start(vlist, ptr);
        char ch;

        while ((ch = *ptr++) != '\0') {
                if (ch == '%' && *ptr != '\0') {
                        ch = *ptr++;
                        switch(ch) {
                        case 'd': printf("%d", va_arg(vlist, int)); break;
                        case 'e': printf("%e", va_arg(vlist, double)); break;
                        case 'c': printf("%c", va_arg(vlist, int)); break;
                        case 's': printf("%s", va_arg(vlist, char *)); break;
                        default: va_end(vlist);exit(1);

                        }

                } else
                        printf("%c", ch);


        }

        va_end(vlist);
        exit(1);
}


int main()
{
        int pid;
        int ptm;
        int pts;
        char *ptr;
        char *program_name[2] = { (char*)"/bin/uname", NULL};
        char buf[512];
        int n;

        if ((ptm = posix_openpt(O_RDWR)) == -1) {
                die("posix_openpt error: %s\n", strerror(errno));
        }
        if (grantpt(ptm) == -1) {
                die("grantpt error: %s\n", strerror(errno));
        }
        if (unlockpt(ptm) == -1) {
                die("unlockpt error: %s\n", strerror(errno));
        }

        pid = fork();
        if (pid < 0) {
                die("fork error: %s\n", strerror(errno));
        } else if (pid == 0) { // child
                if (setsid() == (pid_t)-1) {
                        die("setsid() error: %s\n", strerror(errno));
                }
                if ((ptr = (char *) ptsname(ptm)) == NULL) {
                        die("ptsname error: %s\n", strerror(errno));
                }
                if ((pts = open(ptr, O_RDWR)) < 0) {
                        die("open of slave failed: %a\n", strerror(errno));
                }
                close(ptm);

                if (dup2(pts, STDIN_FILENO) != STDIN_FILENO
                        || dup2(pts, STDOUT_FILENO) != STDOUT_FILENO
                        || dup2(pts, STDERR_FILENO) != STDERR_FILENO) {
                        die("error doing dup's : %s\n", strerror(errno));
                }

                if (execve(*program_name, program_name , NULL) == -1) {
                        die("execve error: %s\n", strerror(errno));
                }
                exit(1);
        } else { // parent
                if (dup2(ptm, STDIN_FILENO) != STDIN_FILENO) {
                        die("dup2 of parent failed");
                }
                while (1) {
                        n = read(ptm, buf, 511);
                        if (n <= 0) {
                                break;
                        }
                        write(STDOUT_FILENO, buf, n);
                }
        }
        return 0;
}