Print to terminal via pts

print-to-terminal-pts.c

#define _GNU_SOURCE
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <signal.h>
#include <string.h>

volatile int running = 1;

void ctrlc_handler(int unused)
{
    running = 0;
}

int main(void) {
    int ptx, pts;
    char *pts_path;
    char tmp_str[256];
    int err = -1;

    signal(SIGINT, ctrlc_handler);

    int ptmx = open("/dev/ptmx", O_RDWR | O_NOCTTY);

    if (ptmx == -1) {
        printf("Open ptmx fail\n");
        goto error0;
    }

    if (unlockpt(ptmx) != 0) {
        printf("Unlock ptmx fail");
        goto error1;
    }

    if (grantpt(ptmx) != 0) {
        printf("Grant ptmx fail");
        goto error1;
    }

    pts_path = ptsname(ptmx);
    pts = open(pts_path, O_WRONLY | O_NOCTTY);

    if (pts == -1) {
        printf("Open pts fail\n");
        goto error1;
    }

    snprintf(tmp_str, 256, "-S%s/%d", pts_path, ptmx);

    switch(fork()) {
    case -1:
        printf("Fork error\n");
        goto error2;

    case 0:
        execl("/usr/bin/xterm", "xterm", tmp_str, (char*)NULL);
        return 0;
    }

    for (int n = 0; (n < 1000) && running; n ++) {
        snprintf(tmp_str, 256, "Fork: N = %i\n", n);
        if (write(pts, tmp_str, strlen(tmp_str) + 1) == -1) {
            printf("Write to pts error\n");
            goto error2;
        }

        printf("Main: N = %i\n", n);
        sleep(1);
    }

    err = 0;

error2:
    close(pts);

error1:
    close(ptmx);

error0:
    return err;
}