1 .\" Copyright 2002 Walter Harms <walter.harms@informatik.uni-oldenburg.de>
2 .\" and Andries Brouwer <aeb@cwi.nl>.
4 .\" %%%LICENSE_START(GPL_NOVERSION_ONELINE)
5 .\" Distributed under GPL
8 .TH TTY_IOCTL 4 2013-11-12 "Linux" "Linux Programmer's Manual"
10 tty_ioctl \- ioctls for terminals and serial lines
12 .B "#include <termios.h>"
14 .BI "int ioctl(int " fd ", int " cmd ", ...);"
18 call for terminals and serial ports accepts many possible command arguments.
19 Most require a third argument, of varying type, here called
26 makes for nonportable programs.
27 Use the POSIX interface described in
30 .SS Get and set terminal attributes
32 .BI "TCGETS struct termios *" argp
34 .IR "tcgetattr(fd, argp)" .
36 Get the current serial port settings.
38 .BI "TCSETS const struct termios *" argp
40 .IR "tcsetattr(fd, TCSANOW, argp)" .
42 Set the current serial port settings.
44 .BI "TCSETSW const struct termios *" argp
46 .IR "tcsetattr(fd, TCSADRAIN, argp)" .
48 Allow the output buffer to drain, and
49 set the current serial port settings.
51 .BI "TCSETSF const struct termios *" argp
53 .IR "tcsetattr(fd, TCSAFLUSH, argp)" .
55 Allow the output buffer to drain, discard pending input, and
56 set the current serial port settings.
58 The following four ioctls are just like
63 except that they take a
66 .IR "struct termios\ *" .
68 .BI "TCGETA struct termio *" argp
70 .BI "TCSETA const struct termio *" argp
72 .BI "TCSETAW const struct termio *" argp
74 .BI "TCSETAF const struct termio *" argp
75 .SS Locking the termios structure
78 structure of a terminal can be locked.
81 structure, with nonzero bits or fields indicating a
84 .BI "TIOCGLCKTRMIOS struct termios *" argp
85 Gets the locking status of the
87 structure of the terminal.
89 .BI "TIOCSLCKTRMIOS const struct termios *" argp
90 Sets the locking status of the
92 structure of the terminal.
93 Only a process with the
95 capability can do this.
96 .SS Get and set window size
97 Window sizes are kept in the kernel, but not used by the kernel
98 (except in the case of virtual consoles, where the kernel will
99 update the window size when the size of the virtual console changes,
100 for example, by loading a new font).
102 The following constants and structure are defined in
105 .BI "TIOCGWINSZ struct winsize *" argp
108 .BI "TIOCSWINSZ const struct winsize *" argp
111 The struct used by these ioctls is defined as
116 unsigned short ws_row;
117 unsigned short ws_col;
118 unsigned short ws_xpixel; /* unused */
119 unsigned short ws_ypixel; /* unused */
124 When the window size changes, a
126 signal is sent to the
127 foreground process group.
130 .BI "TCSBRK int " arg
132 .IR "tcsendbreak(fd, arg)" .
134 If the terminal is using asynchronous serial data transmission, and
136 is zero, then send a break (a stream of zero bits) for between
137 0.25 and 0.5 seconds.
138 If the terminal is not using asynchronous
139 serial data transmission, then either a break is sent, or the function
140 returns without doing anything.
143 is nonzero, nobody knows what will happen.
145 (SVr4, UnixWare, Solaris, Linux treat
146 .I "tcsendbreak(fd,arg)"
153 as a multiplier, and sends a stream of bits
155 times as long as done for zero
159 (when nonzero) as a time interval measured in milliseconds.
163 .BI "TCSBRKP int " arg
164 So-called "POSIX version" of
168 as a timeinterval measured in deciseconds, and does nothing
169 when the driver does not support breaks.
172 Turn break on, that is, start sending zero bits.
175 Turn break off, that is, stop sending zero bits.
176 .SS Software flow control
178 .BI "TCXONC int " arg
180 .IR "tcflow(fd, arg)" .
184 for the argument values
189 .SS Buffer count and flushing
191 .BI "FIONREAD int *" argp
192 Get the number of bytes in the input buffer.
194 .BI "TIOCINQ int *" argp
198 .BI "TIOCOUTQ int *" argp
199 Get the number of bytes in the output buffer.
201 .BI "TCFLSH int " arg
203 .IR "tcflush(fd, arg)" .
207 for the argument values
213 .BI "TIOCSTI const char *" argp
214 Insert the given byte in the input queue.
215 .SS Redirecting console output
218 Redirect output that would have gone to
222 to the given terminal.
223 If that was a pseudoterminal master, send it to the slave.
224 In Linux before version 2.6.10,
225 anybody can do this as long as the output was not redirected yet;
226 since version 2.6.10, only a process with the
228 capability may do this.
229 If output was redirected already
232 but redirection can be stopped by using this ioctl with
238 .SS Controlling terminal
240 .BI "TIOCSCTTY int " arg
241 Make the given terminal the controlling terminal of the calling process.
242 The calling process must be a session leader and not have a
243 controlling terminal already.
246 should be specified as zero.
248 If this terminal is already the controlling terminal
249 of a different session group, then the ioctl fails with
251 unless the caller has the
255 equals 1, in which case the terminal is stolen, and all processes that had
256 it as controlling terminal lose it.
259 If the given terminal was the controlling terminal of the calling process,
260 give up this controlling terminal.
261 If the process was session leader,
266 to the foreground process group
267 and all processes in the current session lose their controlling terminal.
268 .SS Process group and session ID
270 .BI "TIOCGPGRP pid_t *" argp
271 When successful, equivalent to
272 .IR "*argp = tcgetpgrp(fd)" .
274 Get the process group ID of the foreground process group on this terminal.
276 .BI "TIOCSPGRP const pid_t *" argp
278 .IR "tcsetpgrp(fd, *argp)" .
280 Set the foreground process group ID of this terminal.
282 .BI "TIOCGSID pid_t *" argp
283 Get the session ID of the given terminal.
286 in case the terminal is not a master pseudoterminal
287 and not our controlling terminal.
292 Put the terminal into exclusive mode.
295 operations on the terminal are permitted.
298 except for a process with the
303 Disable exclusive mode.
306 .BI "TIOCGETD int *" argp
307 Get the line discipline of the terminal.
309 .BI "TIOCSETD const int *" argp
310 Set the line discipline of the terminal.
311 .SS Pseudoterminal ioctls
313 .BI "TIOCPKT const int *" argp
316 is nonzero) or disable packet mode.
317 Can be applied to the master side of a pseudoterminal only (and will return
320 In packet mode, each subsequent
322 will return a packet that either contains a single nonzero control byte,
323 or has a single byte containing zero (\(aq\0\(aq) followed by data
324 written on the slave side of the pseudoterminal.
325 If the first byte is not
327 (0), it is an OR of one
328 or more of the following bits:
331 TIOCPKT_FLUSHREAD The read queue for the terminal is flushed.
332 TIOCPKT_FLUSHWRITE The write queue for the terminal is flushed.
333 TIOCPKT_STOP Output to the terminal is stopped.
334 TIOCPKT_START Output to the terminal is restarted.
335 TIOCPKT_DOSTOP The start and stop characters are \fB^S\fP/\fB^Q\fP.
336 TIOCPKT_NOSTOP The start and stop characters are not \fB^S\fP/\fB^Q\fP.
339 While this mode is in use, the presence
340 of control status information to be read
341 from the master side may be detected by a
343 for exceptional conditions.
349 to implement a remote-echoed,
350 locally \fB^S\fP/\fB^Q\fP flow-controlled remote login.
357 have not been implemented under Linux.
360 .BI "TIOCMGET int *" argp
361 get the status of modem bits.
363 .BI "TIOCMSET const int *" argp
364 set the status of modem bits.
366 .BI "TIOCMBIC const int *" argp
367 clear the indicated modem bits.
369 .BI "TIOCMBIS const int *" argp
370 set the indicated modem bits.
372 Bits used by these four ioctls:
375 TIOCM_LE DSR (data set ready/line enable)
376 TIOCM_DTR DTR (data terminal ready)
377 TIOCM_RTS RTS (request to send)
378 TIOCM_ST Secondary TXD (transmit)
379 TIOCM_SR Secondary RXD (receive)
380 TIOCM_CTS CTS (clear to send)
381 TIOCM_CAR DCD (data carrier detect)
382 TIOCM_CD see TIOCM_CAR
384 TIOCM_RI see TIOCM_RNG
385 TIOCM_DSR DSR (data set ready)
387 .SS Marking a line as local
389 .BI "TIOCGSOFTCAR int *" argp
390 ("Get software carrier flag")
391 Get the status of the CLOCAL flag in the c_cflag field of the
395 .BI "TIOCSSOFTCAR const int *" argp
396 ("Set software carrier flag")
397 Set the CLOCAL flag in the
401 is nonzero, and clear it otherwise.
405 flag for a line is off, the hardware carrier detect (DCD)
406 signal is significant, and an
408 of the corresponding terminal will block until DCD is asserted,
414 is set, the line behaves as if DCD is always asserted.
415 The software carrier flag is usually turned on for local devices,
416 and is off for lines with modems.
421 .BR console_ioctl (4).
423 .B "#include <linux/tty.h>"
425 .BI "TIOCTTYGSTRUCT struct tty_struct *" argp
431 .\" .SS "Serial info"
432 .\" .BR "#include <linux/serial.h>"
435 .\" .BI "TIOCGSERIAL struct serial_struct *" argp
438 .\" .BI "TIOCSSERIAL const struct serial_struct *" argp
443 system call returns 0 on success.
444 On error, it returns \-1 and sets
450 Invalid command parameter.
460 Insufficient permission.
462 Check the condition of DTR on the serial port.
467 #include <sys/ioctl.h>
474 fd = open("/dev/ttyS0", O_RDONLY);
475 ioctl(fd, TIOCMGET, &serial);
476 if (serial & TIOCM_DTR)
477 puts("TIOCM_DTR is not set");
479 puts("TIOCM_DTR is set");
486 .BR console_ioctl (4),
489 .\" FIONBIO const int *
492 .\" FIOASYNC const int *
494 .\" TIOCSERCONFIG void
495 .\" TIOCSERGWILD int *
496 .\" TIOCSERSWILD const int *
497 .\" TIOCSERGSTRUCT struct async_struct *
498 .\" TIOCSERGETLSR int *
499 .\" TIOCSERGETMULTI struct serial_multiport_struct *
500 .\" TIOCSERSETMULTI const struct serial_multiport_struct *
501 .\" TIOCGSERIAL, TIOCSSERIAL (see above)