miscutils/microcom.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * bare bones 'talk to modem' program - similar to 'cu -l $device'
   4  * inspired by mgetty's microcom
   5  *
   6  * Copyright (C) 2008 by Vladimir Dronnikov <dronnikov@gmail.com>
   7  *
   8  * Licensed under GPLv2, see file LICENSE in this source tree.
   9  */
  10 //config:config MICROCOM
  11 //config:       bool "microcom (5.9 kb)"
  12 //config:       default y
  13 //config:       help
  14 //config:       The poor man's minicom utility for chatting with serial port devices.
  15
  16 //applet:IF_MICROCOM(APPLET(microcom, BB_DIR_USR_BIN, BB_SUID_DROP))
  17
  18 //kbuild:lib-$(CONFIG_MICROCOM) += microcom.o
  19
  20 //usage:#define microcom_trivial_usage
  21 //usage:       "[-d DELAY_MS] [-t TIMEOUT_MS ] [-s SPEED] [-X] TTY"
  22 //usage:#define microcom_full_usage "\n\n"
  23 //usage:       "Copy bytes from stdin to TTY and from TTY to stdout\n"
  24 //usage:     "\n        -d DELAY        Wait up to DELAY ms for TTY output before sending"
  25 //usage:     "\n                        every next byte to it"
  26 //usage:     "\n        -t TIMEOUT      Exit if both stdin and TTY are silent for TIMEOUT ms"
  27 //usage:     "\n        -s SPEED        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         get_termios_and_make_raw(fd, t, oldt, 0
  37                 | TERMIOS_CLEAR_ISIG /* ^C is ASCII char 3, not "interrupt me!" */
  38                 | TERMIOS_RAW_INPUT /* pass all chars verbatim, no special handling or translating CR->NL */
  39                 | TERMIOS_RAW_CRNL  /* dont convert NL<->CR on output too */
  40         );
  41 }
  42
  43 static int xset1(int fd, struct termios *tio, const char *device)
  44 {
  45         int ret = tcsetattr(fd, TCSAFLUSH, tio);
  46
  47         if (ret) {
  48                 bb_perror_msg("can't tcsetattr for %s", device);
  49         }
  50         return ret;
  51 }
  52
  53 int microcom_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  54 int microcom_main(int argc UNUSED_PARAM, char **argv)
  55 {
  56         int sfd;
  57         int nfd;
  58         struct pollfd pfd[2];
  59         struct termios tio0, tiosfd, tio;
  60         char *device_lock_file;
  61         enum {
  62                 OPT_X = 1 << 0, // do not respect Ctrl-X, Ctrl-@
  63                 OPT_s = 1 << 1, // baudrate
  64                 OPT_d = 1 << 2, // wait for device response, ms
  65                 OPT_t = 1 << 3, // timeout, ms
  66         };
  67         speed_t speed = 9600;
  68         int delay = -1;
  69         int timeout = -1;
  70         unsigned opts;
  71
  72         // fetch options
  73         opts = getopt32(argv, "^" "Xs:+d:+t:+" "\0" "=1",
  74                                 &speed, &delay, &timeout
  75         );
  76 //      argc -= optind;
  77         argv += optind;
  78
  79         // try to create lock file in /var/lock
  80         device_lock_file = (char *)bb_basename(argv[0]);
  81         device_lock_file = xasprintf("/var/lock/LCK..%s", device_lock_file);
  82         sfd = open(device_lock_file, O_CREAT | O_WRONLY | O_TRUNC | O_EXCL, 0644);
  83         if (sfd < 0) {
  84                 // device already locked -> bail out
  85                 if (errno == EEXIST)
  86                         bb_perror_msg_and_die("can't create '%s'", device_lock_file);
  87                 // can't create lock -> don't care
  88                 if (ENABLE_FEATURE_CLEAN_UP)
  89                         free(device_lock_file);
  90                 device_lock_file = NULL;
  91         } else {
  92                 // %4d to make concurrent mgetty (if any) happy.
  93                 // Mgetty treats 4-bytes lock files as binary,
  94                 // not text, PID. Making 5+ char file. Brrr...
  95                 fdprintf(sfd, "%4d\n", getpid());
  96                 close(sfd);
  97         }
  98
  99         // setup signals
 100         bb_signals(0
 101                 + (1 << SIGHUP)
 102                 + (1 << SIGINT)
 103                 + (1 << SIGTERM)
 104                 + (1 << SIGPIPE)
 105                 , record_signo);
 106
 107         // error exit code if we fail to open the device
 108         bb_got_signal = 1;
 109
 110         // open device
 111         sfd = open_or_warn(argv[0], O_RDWR | O_NOCTTY | O_NONBLOCK);
 112         if (sfd < 0)
 113                 goto done;
 114         fcntl(sfd, F_SETFL, O_RDWR);
 115
 116         // put device to "raw mode"
 117         xget1(sfd, &tio, &tiosfd);
 118         // set device speed
 119         cfsetspeed(&tio, tty_value_to_baud(speed));
 120         if (xset1(sfd, &tio, argv[0]))
 121                 goto done;
 122
 123         // put stdin to "raw mode" (if stdin is a TTY),
 124         // handle one character at a time
 125         if (isatty(STDIN_FILENO)) {
 126                 xget1(STDIN_FILENO, &tio, &tio0);
 127                 if (xset1(STDIN_FILENO, &tio, "stdin"))
 128                         goto done;
 129         }
 130
 131         // main loop: check with poll(), then read/write bytes across
 132         pfd[0].fd = sfd;
 133         pfd[0].events = POLLIN;
 134         pfd[1].fd = STDIN_FILENO;
 135         pfd[1].events = POLLIN;
 136
 137         bb_got_signal = 0;
 138         nfd = 2;
 139         // Not safe_poll: we want to exit on signal
 140         while (!bb_got_signal && poll(pfd, nfd, timeout) > 0) {
 141                 if (nfd > 1 && pfd[1].revents) {
 142                         char c;
 143                         // read from stdin -> write to device
 144                         if (safe_read(STDIN_FILENO, &c, 1) < 1) {
 145                                 // don't poll stdin anymore if we got EOF/error
 146                                 nfd--;
 147                                 goto skip_write;
 148                         }
 149                         // do we need special processing?
 150                         if (!(opts & OPT_X)) {
 151                                 // ^@ sends Break
 152                                 if (VINTR == c) {
 153                                         tcsendbreak(sfd, 0);
 154                                         goto skip_write;
 155                                 }
 156                                 // ^X exits
 157                                 if (24 == c)
 158                                         break;
 159                         }
 160                         write(sfd, &c, 1);
 161                         if (delay >= 0)
 162                                 safe_poll(pfd, 1, delay);
 163 skip_write: ;
 164                 }
 165                 if (pfd[0].revents) {
 166                         ssize_t len;
 167 #define iobuf bb_common_bufsiz1
 168                         setup_common_bufsiz();
 169                         // read from device -> write to stdout
 170                         len = safe_read(sfd, iobuf, COMMON_BUFSIZE);
 171                         if (len > 0)
 172                                 full_write(STDOUT_FILENO, iobuf, len);
 173                         else {
 174                                 // EOF/error -> bail out
 175                                 bb_got_signal = SIGHUP;
 176                                 break;
 177                         }
 178                 }
 179         }
 180
 181         // restore device mode
 182         tcsetattr(sfd, TCSAFLUSH, &tiosfd);
 183
 184         if (isatty(STDIN_FILENO))
 185                 tcsetattr(STDIN_FILENO, TCSAFLUSH, &tio0);
 186
 187 done:
 188         if (device_lock_file)
 189                 unlink(device_lock_file);
 190
 191         return bb_got_signal;
 192 }