path: root/miscutils/microcom.c (plain)
blob: 04605d883a83e9802e65890290422c635d1cd9d8

1	/* vi: set sw=4 ts=4: */
2	/*
3	* bare bones 'talk to modem' program - similar to 'cu -l $device'
4	* inspired by mgetty's microcom
5	*
6	* Copyright (C) 2008 by Vladimir Dronnikov <dronnikov@gmail.com>
7	*
8	* Licensed under GPLv2, see file LICENSE in this source tree.
9	*/
10	//config:config MICROCOM
11	//config: bool "microcom"
12	//config: default y
13	//config: help
14	//config: The poor man's minicom utility for chatting with serial port devices.
15
16	//applet:IF_MICROCOM(APPLET(microcom, BB_DIR_USR_BIN, BB_SUID_DROP))
17
18	//kbuild:lib-$(CONFIG_MICROCOM) += microcom.o
19
20	//usage:#define microcom_trivial_usage
21	//usage: "[-d DELAY] [-t TIMEOUT] [-s SPEED] [-X] TTY"
22	//usage:#define microcom_full_usage "\n\n"
23	//usage: "Copy bytes for stdin to TTY and from TTY to stdout\n"
24	//usage: "\n -d Wait up to DELAY ms for TTY output before sending every"
25	//usage: "\n next byte to it"
26	//usage: "\n -t Exit if both stdin and TTY are silent for TIMEOUT ms"
27	//usage: "\n -s Set serial line to SPEED"
28	//usage: "\n -X Disable special meaning of NUL and Ctrl-X from stdin"
29
30	#include "libbb.h"
31	#include "common_bufsiz.h"
32
33	// set raw tty mode
34	static void xget1(int fd, struct termios *t, struct termios *oldt)
35	{
36	tcgetattr(fd, oldt);
37	*t = *oldt;
38	cfmakeraw(t);
39	// t->c_lflag &= ~(ISIG|ICANON|ECHO|IEXTEN);
40	// t->c_iflag &= ~(BRKINT|IXON|ICRNL);
41	// t->c_oflag &= ~(ONLCR);
42	// t->c_cc[VMIN] = 1;
43	// t->c_cc[VTIME] = 0;
44	}
45
46	static int xset1(int fd, struct termios *tio, const char *device)
47	{
48	int ret = tcsetattr(fd, TCSAFLUSH, tio);
49
50	if (ret) {
51	bb_perror_msg("can't tcsetattr for %s", device);
52	}
53	return ret;
54	}
55
56	int microcom_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
57	int microcom_main(int argc UNUSED_PARAM, char **argv)
58	{
59	int sfd;
60	int nfd;
61	struct pollfd pfd[2];
62	struct termios tio0, tiosfd, tio;
63	char *device_lock_file;
64	enum {
65	OPT_X = 1 << 0, // do not respect Ctrl-X, Ctrl-@
66	OPT_s = 1 << 1, // baudrate
67	OPT_d = 1 << 2, // wait for device response, ms
68	OPT_t = 1 << 3, // timeout, ms
69	};
70	speed_t speed = 9600;
71	int delay = -1;
72	int timeout = -1;
73	unsigned opts;
74
75	// fetch options
76	opts = getopt32(argv, "Xs:+d:+t:+", &speed, &delay, &timeout);
77	// argc -= optind;
78	argv += optind;
79
80	// try to create lock file in /var/lock
81	device_lock_file = (char *)bb_basename(argv[0]);
82	device_lock_file = xasprintf("/var/lock/LCK..%s", device_lock_file);
83	sfd = open(device_lock_file, O_CREAT | O_WRONLY | O_TRUNC | O_EXCL, 0644);
84	if (sfd < 0) {
85	// device already locked -> bail out
86	if (errno == EEXIST)
87	bb_perror_msg_and_die("can't create '%s'", device_lock_file);
88	// can't create lock -> don't care
89	if (ENABLE_FEATURE_CLEAN_UP)
90	free(device_lock_file);
91	device_lock_file = NULL;
92	} else {
93	// %4d to make concurrent mgetty (if any) happy.
94	// Mgetty treats 4-bytes lock files as binary,
95	// not text, PID. Making 5+ char file. Brrr...
96	fdprintf(sfd, "%4d\n", getpid());
97	close(sfd);
98	}
99
100	// setup signals
101	bb_signals(0
102	+ (1 << SIGHUP)
103	+ (1 << SIGINT)
104	+ (1 << SIGTERM)
105	+ (1 << SIGPIPE)
106	, record_signo);
107
108	// error exit code if we fail to open the device
109	bb_got_signal = 1;
110
111	// open device
112	sfd = open_or_warn(argv[0], O_RDWR | O_NOCTTY | O_NONBLOCK);
113	if (sfd < 0)
114	goto done;
115	fcntl(sfd, F_SETFL, O_RDWR);
116
117	// put device to "raw mode"
118	xget1(sfd, &tio, &tiosfd);
119	// set device speed
120	cfsetspeed(&tio, tty_value_to_baud(speed));
121	if (xset1(sfd, &tio, argv[0]))
122	goto done;
123
124	// put stdin to "raw mode" (if stdin is a TTY),
125	// handle one character at a time
126	if (isatty(STDIN_FILENO)) {
127	xget1(STDIN_FILENO, &tio, &tio0);
128	if (xset1(STDIN_FILENO, &tio, "stdin"))
129	goto done;
130	}
131
132	// main loop: check with poll(), then read/write bytes across
133	pfd[0].fd = sfd;
134	pfd[0].events = POLLIN;
135	pfd[1].fd = STDIN_FILENO;
136	pfd[1].events = POLLIN;
137
138	bb_got_signal = 0;
139	nfd = 2;
140	// Not safe_poll: we want to exit on signal
141	while (!bb_got_signal && poll(pfd, nfd, timeout) > 0) {
142	if (nfd > 1 && pfd[1].revents) {
143	char c;
144	// read from stdin -> write to device
145	if (safe_read(STDIN_FILENO, &c, 1) < 1) {
146	// don't poll stdin anymore if we got EOF/error
147	nfd--;
148	goto skip_write;
149	}
150	// do we need special processing?
151	if (!(opts & OPT_X)) {
152	// ^@ sends Break
153	if (VINTR == c) {
154	tcsendbreak(sfd, 0);
155	goto skip_write;
156	}
157	// ^X exits
158	if (24 == c)
159	break;
160	}
161	write(sfd, &c, 1);
162	if (delay >= 0)
163	safe_poll(pfd, 1, delay);
164	skip_write: ;
165	}
166	if (pfd[0].revents) {
167	ssize_t len;
168	#define iobuf bb_common_bufsiz1
169	setup_common_bufsiz();
170	// read from device -> write to stdout
171	len = safe_read(sfd, iobuf, COMMON_BUFSIZE);
172	if (len > 0)
173	full_write(STDOUT_FILENO, iobuf, len);
174	else {
175	// EOF/error -> bail out
176	bb_got_signal = SIGHUP;
177	break;
178	}
179	}
180	}
181
182	// restore device mode
183	tcsetattr(sfd, TCSAFLUSH, &tiosfd);
184
185	if (isatty(STDIN_FILENO))
186	tcsetattr(STDIN_FILENO, TCSAFLUSH, &tio0);
187
188	done:
189	if (device_lock_file)
190	unlink(device_lock_file);
191
192	return bb_got_signal;
193	}
194