ioctls для терминалов и последовательных линий (ioctls for terminals and serial lines)
Описание (Description)
The ioctl(2) call for terminals and serial ports accepts many
possible command arguments. Most require a third argument, of
varying type, here called argp or arg.
Use of ioctl() makes for nonportable programs. Use the POSIX
interface described in termios(3) whenever possible.
Get and set terminal attributes
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
Locking the termios structure
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.
Get and set window size
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.
Sending a break
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.
Software flow control
TCXONC Argument: int arg
Equivalent to tcflow(fd, arg).
See tcflow(3) for the argument values TCOOFF, TCOON,
TCIOFF, TCION.
Buffer count and flushing
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.
Faking input
TIOCSTI
Argument: const char *argp
Insert the given byte in the input queue.
Redirecting console output
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.
Controlling terminal
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.
Process group and session ID
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.
Exclusive mode
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.
Line discipline
TIOCGETD
Argument: int *argp
Get the line discipline of the terminal.
TIOCSETD
Argument: const int *argp
Set the line discipline of the terminal.
Pseudoterminal ioctls
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:
TIOCPKT_FLUSHREAD The read queue for the
terminal is flushed.
TIOCPKT_FLUSHWRITE The write queue for the
terminal is flushed.
TIOCPKT_STOP Output to the terminal
is stopped.
TIOCPKT_START Output to the terminal
is restarted.
TIOCPKT_DOSTOP The start and stop
characters are ^S/^Q.
TIOCPKT_NOSTOP The start and stop
characters are not
^S/^Q.
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.
Modem control
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:
TIOCM_LE DSR (data set ready/line enable)
TIOCM_DTR DTR (data terminal ready)
TIOCM_RTS RTS (request to send)
TIOCM_ST Secondary TXD (transmit)
TIOCM_SR Secondary RXD (receive)
TIOCM_CTS CTS (clear to send)
TIOCM_CAR DCD (data carrier detect)
TIOCM_CD see TIOCM_CAR
TIOCM_RNG RNG (ring)
TIOCM_RI see TIOCM_RNG
TIOCM_DSR DSR (data set ready)
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.
Marking a line as local
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.
Linux-specific
For the TIOCLINUX ioctl, see ioctl_console(2).
Kernel debugging
#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.
