Manpages - ioctl_tty.2

TCGETS

Argument: *struct termios **/argp/

Equivalent to tcgetattr(fd, argp).

Get the current serial port settings.

TCSETS

Argument: *const struct termios **/argp/

Equivalent to tcsetattr(fd, TCSANOW, argp).

Set the current serial port settings.

TCSETSW

Argument: *const struct termios **/argp/

Equivalent to tcsetattr(fd, TCSADRAIN, argp).

Allow the output buffer to drain, and set the current serial port settings.

TCSETSF

Argument: *const struct termios **/argp/

Equivalent to tcsetattr(fd, TCSAFLUSH, argp).

Allow the output buffer to drain, discard pending input, and set the current serial port settings.

The following four ioctls, added in Linux 2.6.20, are just like TCGETS, TCSETS, TCSETSW, TCSETSF, except that they take a struct termios2 * instead of a struct termios *. If the structure member c_cflag contains the flag BOTHER, then the baud rate is stored in the structure members c_ispeed and c_ospeed as integer values. These ioctls are not supported on all architectures.

TCGETS2	*struct termios2 **argp
TCSETS2	*const struct termios2 **argp
TCSETSW2	*const struct termios2 **argp
TCSETSF2	*const struct termios2 **argp

The following four ioctls are just like TCGETS, TCSETS, TCSETSW, TCSETSF, except that they take a struct termio * instead of a struct termios *.

TCGETA	*struct termio **argp
TCSETA	*const struct termio **argp
TCSETAW	*const struct termio **argp
TCSETAF	*const struct termio **argp

The termios structure of a terminal can be locked. The lock is itself a termios structure, with nonzero bits or fields indicating a locked value.

TIOCGLCKTRMIOS

Argument: *struct termios **/argp/

Gets the locking status of the termios structure of the terminal.

TIOCSLCKTRMIOS

Argument: *const struct termios **/argp/

Sets the locking status of the termios structure of the terminal. Only a process with the CAP_SYS_ADMIN capability can do this.

Window sizes are kept in the kernel, but not used by the kernel (except in the case of virtual consoles, where the kernel will update the window size when the size of the virtual console changes, for example, by loading a new font).

TIOCGWINSZ

Argument: *struct winsize **/argp/

Get window size.

TIOCSWINSZ

Argument: *const struct winsize **/argp/

Set window size.

The struct used by these ioctls is defined as

  struct winsize {
      unsigned short ws_row;
      unsigned short ws_col;
      unsigned short ws_xpixel;   /* unused */
      unsigned short ws_ypixel;   /* unused */
  };

When the window size changes, a SIGWINCH signal is sent to the foreground process group.

TCSBRK

Argument: *int */arg/

Equivalent to tcsendbreak(fd, arg).

If the terminal is using asynchronous serial data transmission, and arg is zero, then send a break (a stream of zero bits) for between 0.25 and 0.5 seconds. If the terminal is not using asynchronous serial data transmission, then either a break is sent, or the function returns without doing anything. When arg is nonzero, nobody knows what will happen.

(SVr4, UnixWare, Solaris, and Linux treat tcsendbreak(fd,arg) with nonzero arg like tcdrain(fd). SunOS treats arg as a multiplier, and sends a stream of bits arg times as long as done for zero arg. DG/UX and AIX treat arg (when nonzero) as a time interval measured in milliseconds. HP-UX ignores arg.)

TCSBRKP

Argument: *int */arg/

So-called “POSIX version” of TCSBRK. It treats nonzero arg as a time interval measured in deciseconds, and does nothing when the driver does not support breaks.

TIOCSBRK

Argument: void

Turn break on, that is, start sending zero bits.

TIOCCBRK

Argument: void

Turn break off, that is, stop sending zero bits.

TCXONC

Argument: *int */arg/

Equivalent to tcflow(fd, arg).

See tcflow*(3) for the argument values *TCOOFF, TCOON, TCIOFF, TCION.

FIONREAD

Argument: *int **/argp/

Get the number of bytes in the input buffer.

TIOCINQ

Argument: *int **/argp/

Same as FIONREAD.

TIOCOUTQ

Argument: *int **/argp/

Get the number of bytes in the output buffer.

TCFLSH

Argument: *int */arg/

Equivalent to tcflush(fd, arg).

See tcflush*(3) for the argument values *TCIFLUSH, TCOFLUSH, TCIOFLUSH.

TIOCSTI

Argument: *const char **/argp/

Insert the given byte in the input queue.

TIOCCONS

Argument: void

Redirect output that would have gone to /dev/console or /dev/tty0 to the given terminal. If that was a pseudoterminal master, send it to the slave. In Linux before version 2.6.10, anybody can do this as long as the output was not redirected yet; since version 2.6.10, only a process with the CAP_SYS_ADMIN capability may do this. If output was redirected already, then EBUSY is returned, but redirection can be stopped by using this ioctl with fd pointing at /dev/console or /dev/tty0.

TIOCSCTTY

Argument: *int */arg/

Make the given terminal the controlling terminal of the calling process. The calling process must be a session leader and not have a controlling terminal already. For this case, arg should be specified as zero.

If this terminal is already the controlling terminal of a different session group, then the ioctl fails with EPERM, unless the caller has the CAP_SYS_ADMIN capability and arg equals 1, in which case the terminal is stolen, and all processes that had it as controlling terminal lose it.

TIOCNOTTY

Argument: void

If the given terminal was the controlling terminal of the calling process, give up this controlling terminal. If the process was session leader, then send SIGHUP and SIGCONT to the foreground process group and all processes in the current session lose their controlling terminal.

TIOCGPGRP

Argument: *pid_t **/argp/

When successful, equivalent to *argp = tcgetpgrp(fd).

Get the process group ID of the foreground process group on this terminal.

TIOCSPGRP

Argument: *const pid_t **/argp/

Equivalent to tcsetpgrp(fd, *argp).

Set the foreground process group ID of this terminal.

TIOCGSID

Argument: *pid_t **/argp/

Get the session ID of the given terminal. This fails with the error ENOTTY if the terminal is not a master pseudoterminal and not our controlling terminal. Strange.

TIOCEXCL

Argument: void

Put the terminal into exclusive mode. No further open*(2) operations on the terminal are permitted. (They fail with *EBUSY, except for a process with the CAP_SYS_ADMIN capability.)

TIOCGEXCL

Argument: *int **/argp/

(since Linux 3.8) If the terminal is currently in exclusive mode, place a nonzero value in the location pointed to by argp; otherwise, place zero in *argp.

TIOCNXCL

Argument: void

Disable exclusive mode.

TIOCGETD

Argument: *int **/argp/

Get the line discipline of the terminal.

TIOCSETD

Argument: *const int **/argp/

Set the line discipline of the terminal.

TIOCPKT

Argument: *const int **/argp/

Enable (when argp is nonzero) or disable packet mode. Can be applied to the master side of a pseudoterminal only (and will return *ENOTTY otherwise). In packet mode, each subsequent read*(2) will return a packet that either contains a single nonzero control byte, or has a single byte containing zero (’\0’) followed by data written on the slave side of the pseudoterminal. If the first byte is not *TIOCPKT_DATA (0), it is an OR of one or more of the following bits:

While packet mode is in use, the presence of control status information to be read from the master side may be detected by a select*(2) for exceptional conditions or a *poll*(2) for the *POLLPRI event.

This mode is used by rlogin*(1) and *rlogind*(8) to implement a remote-echoed, locally *^S*/*^Q flow-controlled remote login.

TIOCGPKT

Argument: *const int **/argp/

(since Linux 3.8) Return the current packet mode setting in the integer pointed to by argp.

TIOCSPTLCK

Argument: *int **/argp/

Set (if *argp is nonzero) or remove (if *argp is zero) the lock on the pseudoterminal slave device. (See also *unlockpt*(3).)

TIOCGPTLCK

Argument: *int **/argp/

(since Linux 3.8) Place the current lock state of the pseudoterminal slave device in the location pointed to by argp.

TIOCGPTPEER

Argument: *int */flags/

(since Linux 4.13) Given a file descriptor in fd that refers to a pseudoterminal master, open (with the given *open*(2)-style flags) and return a new file descriptor that refers to the peer pseudoterminal slave device. This operation can be performed regardless of whether the pathname of the slave device is accessible through the calling process’s mount namespace.

Security-conscious programs interacting with namespaces may wish to use this operation rather than *open*(2) with the pathname returned by *ptsname*(3), and similar library functions that have insecure APIs. (For example, confusion can occur in some cases using *ptsname*(3) with a pathname where a devpts filesystem has been mounted in a different mount namespace.)

The BSD ioctls TIOCSTOP, TIOCSTART, TIOCUCNTL, and TIOCREMOTE have not been implemented under Linux.

TIOCMGET

Argument: *int **/argp/

Get the status of modem bits.

TIOCMSET

Argument: *const int **/argp/

Set the status of modem bits.

TIOCMBIC

Argument: *const int **/argp/

Clear the indicated modem bits.

TIOCMBIS

Argument: *const int **/argp/

Set the indicated modem bits.

The following bits are used by the above ioctls:

TIOCMIWAIT

Argument: *int */arg/

Wait for any of the 4 modem bits (DCD, RI, DSR, CTS) to change. The bits of interest are specified as a bit mask in arg, by ORing together any of the bit values, TIOCM_RNG, TIOCM_DSR, TIOCM_CD, and TIOCM_CTS. The caller should use TIOCGICOUNT to see which bit has changed.

TIOCGICOUNT

Argument: *struct serial_icounter_struct **/argp/

Get counts of input serial line interrupts (DCD, RI, DSR, CTS). The counts are written to the serial_icounter_struct structure pointed to by argp.

Note: both 1->0 and 0->1 transitions are counted, except for RI, where only 0->1 transitions are counted.

TIOCGSOFTCAR

Argument: *int **/argp/

(“Get software carrier flag”) Get the status of the CLOCAL flag in the c_cflag field of the termios structure.

TIOCSSOFTCAR

Argument: *const int **/argp/

(“Set software carrier flag”) Set the CLOCAL flag in the termios structure when */argp/ is nonzero, and clear it otherwise.

If the CLOCAL flag for a line is off, the hardware carrier detect (DCD) signal is significant, and an open*(2) of the corresponding terminal will block until DCD is asserted, unless the *O_NONBLOCK flag is given. If CLOCAL is set, the line behaves as if DCD is always asserted. The software carrier flag is usually turned on for local devices, and is off for lines with modems.

For the TIOCLINUX ioctl, see *ioctl_console*(2).

#include <linux/tty.h>

TIOCTTYGSTRUCT

Argument: *struct tty_struct **/argp/

Get the tty_struct corresponding to fd. This command was removed in Linux 2.5.67.