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cttyhack: print detected ctty name when called without parameters
Sometimes there's a need to figure out the controlling tty from a shell script, for example, to obtain a line for getty. In this case it's easier to call cttyhack than trying to repeat some of the cttyhack's logic. function old new delta cttyhack_main 283 327 +44 packed_usage 28911 28915 +4 Signed-off-by: Alexander Shishkin <virtuoso@slind.org> Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
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@ -50,9 +50,12 @@
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//config:
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//config: # exec setsid sh -c 'exec sh </dev/tty1 >/dev/tty1 2>&1'
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//config:
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//config: Starting getty on a controlling tty from a shell script:
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//config:
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//config: # getty 115200 $(cttyhack)
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//usage:#define cttyhack_trivial_usage
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//usage: "PROG ARGS"
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//usage: "[PROG ARGS]"
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//usage:#define cttyhack_full_usage "\n\n"
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//usage: "Give PROG a controlling tty if possible."
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//usage: "\nExample for /etc/inittab (for busybox init):"
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@ -108,20 +111,29 @@ int cttyhack_main(int argc UNUSED_PARAM, char **argv)
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char paranoia[sizeof(struct serial_struct) * 3];
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} u;
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if (!*++argv) {
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bb_show_usage();
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}
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strcpy(console, "/dev/tty");
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fd = open(console, O_RDWR);
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if (fd >= 0) {
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/* We already have ctty, nothing to do */
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close(fd);
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} else {
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if (fd < 0) {
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/* We don't have ctty (or don't have "/dev/tty" node...) */
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do {
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#ifdef __linux__
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int s = open_read_close("/sys/class/tty/console/active",
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int s;
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if (ioctl(0, VT_GETSTATE, &u.vt) == 0) {
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/* this is linux virtual tty */
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sprintf(console + 8, "S%u" + 1, (int)u.vt.v_active);
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break;
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}
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#endif
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#ifdef TIOCGSERIAL
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if (ioctl(0, TIOCGSERIAL, &u.sr) == 0) {
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/* this is a serial console; assuming it is named /dev/ttySn */
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sprintf(console + 8, "S%u", (int)u.sr.line);
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break;
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}
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#endif
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#ifdef __linux__
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/* Note that this method is not related to _stdin_ */
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s = open_read_close("/sys/class/tty/console/active",
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console + 5, sizeof(console) - 5);
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if (s > 0) {
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/* found active console via sysfs (Linux 2.6.38+)
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@ -130,39 +142,35 @@ int cttyhack_main(int argc UNUSED_PARAM, char **argv)
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console[4 + s] = '\0';
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break;
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}
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if (ioctl(0, VT_GETSTATE, &u.vt) == 0) {
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/* this is linux virtual tty */
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sprintf(console + 8, "S%d" + 1, u.vt.v_active);
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break;
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}
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#endif
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#ifdef TIOCGSERIAL
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if (ioctl(0, TIOCGSERIAL, &u.sr) == 0) {
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/* this is a serial console; assuming it is named /dev/ttySn */
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sprintf(console + 8, "S%d", u.sr.line);
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break;
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}
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#endif
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/* nope, could not find it */
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goto ret;
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console[0] = '\0';
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} while (0);
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}
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argv++;
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if (!argv[0]) {
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if (!console[0])
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return EXIT_FAILURE;
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puts(console);
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return EXIT_SUCCESS;
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}
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if (fd < 0) {
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fd = open_or_warn(console, O_RDWR);
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if (fd < 0)
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goto ret;
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//bb_error_msg("switching to '%s'", console);
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dup2(fd, 0);
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dup2(fd, 1);
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dup2(fd, 2);
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while (fd > 2)
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close(fd--);
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/* Some other session may have it as ctty,
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* steal it from them:
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*/
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ioctl(0, TIOCSCTTY, 1);
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}
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ret:
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//bb_error_msg("switching to '%s'", console);
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dup2(fd, 0);
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dup2(fd, 1);
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dup2(fd, 2);
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while (fd > 2)
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close(fd--);
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/* Some other session may have it as ctty,
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* try to steal it from them:
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*/
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ioctl(0, TIOCSCTTY, 1);
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ret:
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BB_EXECVP_or_die(argv);
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}
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