1/*
2 * resizewin
3 *
4 * Query terminal for size and inform the kernel
5 *
6 * Copyright 2015 EMC / Isilon Storage Division
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 */
29
30#include <sys/cdefs.h>
31#include <sys/ioctl.h>
32#include <sys/time.h>
33#include <err.h>
34#include <errno.h>
35#include <fcntl.h>
36#include <stdio.h>
37#include <stdlib.h>
38#include <strings.h>
39#include <termios.h>
40#include <unistd.h>
41
42/* screen doesn't support ESC[18t (return terminal size) so do it the hard way */
43static const char query[] =
44    "\0337"		/* Save cursor position */
45    "\033[r"		/* Scroll whole screen */
46    "\033[999;999H"	/* Move cursor */
47    "\033[6n"		/* Get cursor position */
48    "\0338";		/* Restore cursor position */
49
50static void
51usage(void)
52{
53
54	fprintf(stderr, "usage: resizewin [-z]\n");
55	exit(1);
56}
57
58int
59main(int argc, char **argv)
60{
61	struct termios old, new;
62	struct winsize w;
63	struct timeval then, now;
64	char data[20];
65	int ch, cnt, error, fd, ret, zflag;
66
67	error = 0;
68	zflag = 0;
69	while ((ch = getopt(argc, argv, "z")) != -1) {
70		switch (ch) {
71		case 'z':
72			zflag = 1;
73			break;
74		case '?':
75		default:
76			usage();
77		}
78	}
79	argc -= optind;
80	if (argc != 0)
81		usage();
82
83	if ((fd = open("/dev/tty", O_RDWR | O_NONBLOCK)) == -1)
84		exit(1);
85
86	if (zflag) {
87		if (ioctl(fd, TIOCGWINSZ, &w) == -1)
88			exit(1);
89		if (w.ws_row != 0 && w.ws_col != 0)
90			exit(0);
91	}
92
93	/* Disable echo, flush the input, and drain the output */
94	if (tcgetattr(fd, &old) == -1)
95		exit(1);
96
97	new = old;
98	new.c_cflag |= (CLOCAL | CREAD);
99	new.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);
100	if (tcsetattr(fd, TCSAFLUSH, &new) == -1)
101		exit(1);
102
103	if (write(fd, query, sizeof(query) - 1) != sizeof(query) - 1) {
104		error = 1;
105		goto out;
106	}
107
108	/* Read the response */
109	bzero(data, sizeof(data));
110	gettimeofday(&then, NULL);
111	cnt = 0;
112	while (1) {
113		ret = read(fd, data + cnt, 1);
114
115		if (ret == -1) {
116			if (errno == EAGAIN) {
117				gettimeofday(&now, NULL);
118				timersub(&now, &then, &now);
119				if (now.tv_sec >= 2) {
120					warnx("timeout reading from terminal");
121					error = 1;
122					goto out;
123				}
124
125				usleep(20000);
126				continue;
127			}
128			error = 1;
129			goto out;
130		}
131		if (data[cnt] == 'R')
132			break;
133
134		cnt++;
135		if (cnt == sizeof(data) - 2) {
136			warnx("response too long");
137			error = 1;
138			goto out;
139		}
140	}
141
142	/* Parse */
143	if (sscanf(data, "\033[%hu;%huR", &w.ws_row, &w.ws_col) != 2) {
144		error = 1;
145		warnx("unable to parse response");
146		goto out;
147	}
148
149	/* Finally, what we want */
150	if (ioctl(fd, TIOCSWINSZ, &w) == -1)
151		error = 1;
152 out:
153	/* Restore echo */
154	tcsetattr(fd, TCSANOW, &old);
155
156	close(fd);
157	exit(error);
158}
159