Small util to detect if a terminal does or does not support terminal titles.

detect-title.c

/* Copyright © 2015 Ada Worcester <oss@ada.pihq.com>
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#define _XOPEN_SOURCE 700
#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <termios.h>
#include <unistd.h>

static int fd_getc(int f)
{
	char buf;
	ssize_t len;
	int old_errno;

	old_errno = errno;
	len = read(f, &buf, 1);
	if(len == 0) errno = old_errno;
	if(len <= 0) return EOF;
	return buf;
}

static int read_pos(int fd, int *x, int *y)
{
	int c;
	*x = 0; *y = 0;
	if(dprintf(fd, "\033[6n") < 0) return -1;
	errno = 0;
	if(fd_getc(fd) != '\033') {
		if(errno == 0) errno = EINVAL;
		return -1;
	}
	if(fd_getc(fd) != '[') {
		if(errno == 0) errno = EINVAL;
		return -1;
	}

	while((c = fd_getc(fd)) != ';') {
		if(!(c >= '0' && c <= '9')) {
			if(errno == 0) errno = EINVAL;
			return -1;
		}
		*x *= 10;
		*x += c - '0';
	}

	while((c = fd_getc(fd)) != 'R') {
		if(!(c >= '0' && c <= '9')) {
			if(errno == 0) errno = EINVAL;
			return -1;
		}
		*y *= 10;
		*y += c - '0';
	}
	return 0;
}

static void die()
{
	perror("detect-title");
	exit(1);
}

static struct termios orig_termios;
static int term_fd;
static void atexit_handler(void)
{
	tcsetattr(term_fd, TCSANOW, &orig_termios);
}


int main()
{
	struct termios termios;
	sigset_t set, oldset;
	int x1, y1, x2, y2;
	int orig_err;

	sigfillset(&set);

	term_fd = open("/dev/tty", O_RDWR);
	if(term_fd < 0) die();

	if(tcgetattr(term_fd, &orig_termios) < 0) die();
	termios = orig_termios;
	termios.c_lflag &= ~(ECHO | ICANON | IEXTEN | ISIG | CREAD);
	termios.c_iflag &= ~(BRKINT | ICRNL | INPCK | IXON);
	termios.c_cflag &= ~(CSIZE | PARENB);
	termios.c_cflag |= CS8;
	termios.c_oflag &= ~(OPOST);
	termios.c_cc[VMIN] = 1;
	termios.c_cc[VTIME] = 0;

	sigprocmask(SIG_BLOCK, &set, &oldset);

	atexit(atexit_handler);

	if(tcsetattr(term_fd, TCSAFLUSH, &termios) < 0) die();

	if(read_pos(term_fd, &x1, &y1)) die();
	if(dprintf(term_fd, "\033]0;testing\033\\") < 0) die();
	if(read_pos(term_fd, &x2, &y2)) die();
	if(dprintf(term_fd, "\033[%d;%dH\033[J", x1, y1) < 0) die();

	if(tcsetattr(term_fd, TCSANOW, &orig_termios) < 0) die();

	sigprocmask(SIG_SETMASK, &oldset, 0);

	if(x1 == x2 && y1 == y2) {
		if(dprintf(1, "yes\n") < 0) die();
	} else {
		if(dprintf(1, "no\n") < 0) die();
	}

	return 0;
}