TTY(4)TTY(4)NAMEtty - general terminal interface
SYNOPSIS
#include <sgtty.h>
DESCRIPTION
This section describes both a particular special file /dev/tty and the
terminal drivers used for conversational computing.
Line Disciplines
The system provides different line disciplines for controlling
communications lines. In this version of the system there are two
disciplines available for use with terminals:
old The old (Version 7) terminal driver. This is sometimes used
when using the standard shell sh(1).
new The standard Berkeley terminal driver, with features for job
control; this must be used when using csh(1).
Line discipline switching is accomplished with the TIOCSETD ioctl:
int ldisc = LDISC;
ioctl(f, TIOCSETD, &ldisc);
where LDISC is OTTYDISC for the standard tty driver and NTTYDISC for
the ``new'' driver. The standard (currently old) tty driver is
discipline 0 by convention. Other disciplines may exist for special
purposes, such as use of communications lines for network connections.
The current line discipline can be obtained with the TIOCGETD ioctl.
Pending input is discarded when the line discipline is changed.
All of the low-speed asynchronous communications ports can use any of
the available line disciplines, no matter what hardware is involved.
The remainder of this section discusses the “old” and “new”
disciplines.
The Control Terminal
When a terminal file is opened, it causes the process to wait until a
connection is established. In practice, user programs seldom open
these files; they are opened by getty(8) or rlogind(8C) and become a
user's standard input and output file.
If a process which has no control terminal opens a terminal file, then
that terminal file becomes the control terminal for that process. The
control terminal is thereafter inherited by a child process during a
fork(2), even if the control terminal is closed.
The file /dev/tty is, in each process, a synonym for a control terminal
associated with that process. It is useful for programs that wish to
be sure of writing messages on the terminal no matter how output has
been redirected. It can also be used for programs that demand a file
name for output, when typed output is desired and it is tiresome to
find out which terminal is currently in use.
A process can remove the association it has with its controlling
terminal by opening the file /dev/tty and issuing an
ioctl(f, TIOCNOTTY, 0);
This is often desirable in server processes.
Process Group
Command processors such as csh(1) can arbitrate the terminal between
different jobs by placing related jobs in a single process group and
associating this process group with the terminal. A terminal's
associated process group may be set using the TIOCSPGRP ioctl(2):
ioctl(fildes, TIOCSPGRP, &pgrp);
or examined using TIOCGPGRP, which returns the current process group in
pgrp. The new terminal driver aids in this arbitration by restricting
access to the terminal by processes which are not in the current
process group; see Job access control below.
Modes.
The terminal drivers have three major modes, characterized by the
amount of processing on the input and output characters:
cooked The normal mode. In this mode lines of input are collected
and input editing is done. The edited line is made available
when it is completed by a newline, or when the t_brkc
character (normally undefined) or t_eofc character (normally
an EOT, control-D, hereafter ^D) is entered. A carriage
return is usually made synonymous with newline in this mode,
and replaced with a newline whenever it is typed. All driver
functions (input editing, interrupt generation, output
processing such as delay generation and tab expansion, etc.)
are available in this mode.
CBREAK This mode eliminates the character, word, and line editing
input facilities, making the input character available to the
user program as it is typed. Flow control, literal-next and
interrupt processing are still done in this mode. Output
processing is done.
RAW This mode eliminates all input processing and makes all input
characters available as they are typed; no output processing
is done either.
The style of input processing can also be very different when the
terminal is put in non-blocking I/O mode; see the FNDELAY flag
described in fcntl(2). In this case a read(2) from the control
terminal will never block, but rather return an error indication
(EWOULDBLOCK) if there is no input available.
A process may also request that a SIGIO signal be sent it whenever
input is present and also whenever output queues fall below the low-
water mark. To enable this mode the FASYNC flag should be set using
fcntl(2).
Input Editing
A UNIX terminal ordinarily operates in full-duplex mode. Characters
may be typed at any time, even while output is occurring, and are only
lost when the system's character input buffers become completely
choked, which is rare, or when the user has accumulated the maximum
allowed number of input characters that have not yet been read by some
program. Currently this limit is 256 characters. In RAW mode, the
terminal driver throws away all input and output without notice when
the limit is reached. In CBREAK or cooked mode it refuses to accept
any further input and, if in the new line discipline, rings the
terminal bell.
Input characters are normally accepted in either even or odd parity
with the parity bit being stripped off before the character is given to
the program. By clearing either the EVEN or ODD bit in the flags word
it is possible to have input characters with that parity discarded (see
the Summary below.) If neither EVEN nor ODD is specified, both parity
characters are accepted and the parity bit is stripped.
In all of the line disciplines, it is possible to simulate terminal
input using the TIOCSTI ioctl, which takes, as its third argument, the
address of a character. The system pretends that this character was
typed on the argument terminal, which must be the control terminal
except for the super-user (this call is not in standard version 7
UNIX).
Input characters are normally echoed by putting them in an output queue
as they arrive. This may be disabled by clearing the ECHO bit in the
flags word using the stty(3C) call or the TIOCSETN or TIOCSETP ioctls
(see the Summary below).
In cooked mode, terminal input is processed in units of lines. A
program attempting to read will normally be suspended until an entire
line has been received (but see the description of SIGTTIN in Job
access control and of FIONREAD in Summary, both below.) No matter how
many characters are requested in the read call, at most one line will
be returned. It is not, however, necessary to read a whole line at
once; any number of characters may be requested in a read, even one,
without losing information.
During input, line editing is normally done, with the erase character
sg_erase (by default, DELETE) logically erasing the last character
typed and the sg_kill character (default, ^U: control-U) logically
erasing the entire current input line. These characters never erase
beyond the beginning of the current input line or an eof. These
characters may be entered literally by preceding them with `\'; the `\'
will normally be erased when the character is typed.
The drivers normally treat either a carriage return or a newline
character as terminating an input line, replacing the return with a
newline and echoing a return and a line feed. If the CRMOD bit is
cleared in the local mode word then the processing for carriage return
is disabled, and it is simply echoed as a return, and does not
terminate cooked mode input.
In the new driver there is a literal-next character (normally ^V) which
can be typed in both cooked and CBREAK mode preceding any character to
prevent its special meaning to the terminal handler. This is to be
preferred to the use of `\' escaping erase and kill characters, but `\'
is retained with its old function in the new line discipline.
The new terminal driver also provides two other editing characters in
normal mode. The word-erase character, normally ^W, erases the
preceding word, but not any spaces before it. For the purposes of ^W,
a word is defined as a sequence of non-blank characters, with tabs
counted as blanks. Finally, the reprint character, normally ^R,
retypes the pending input beginning on a new line. Retyping occurs
automatically in cooked mode if characters which would normally be
erased from the screen are fouled by program output.
Input Echoing and Redisplay
The terminal driver has several modes (not present in standard UNIX
Version 7 systems) for handling the echoing of terminal input,
controlled by bits in a local mode word.
Hardcopy terminals. When a hardcopy terminal is in use, the LPRTERA
bit is normally set in the local mode word. Characters which are
logically erased are then printed out backwards preceded by `\' and
followed by `/' in this mode.
CRT terminals. When a CRT terminal is in use, the LCRTBS bit is
normally set in the local mode word. The terminal driver then echoes
the proper number of erase characters when input is erased; in the
normal case where the erase character is a ^H this causes the cursor of
the terminal to back up to where it was before the logically erased
character was typed. If the input has become fouled due to
interspersed asynchronous output, the input is automatically retyped.
Erasing characters from a CRT. When a CRT terminal is in use, the
LCRTERA bit may be set to cause input to be erased from the screen with
a “backspace-space-backspace” sequence when character or word deleting
sequences are used. A LCRTKIL bit may be set as well, causing the
input to be erased in this manner on line kill sequences as well.
Echoing of control characters. If the LCTLECH bit is set in the local
state word, then non-printing (control) characters are normally echoed
as ^X (for some X) rather than being echoed unmodified; delete is
echoed as ^?.
The normal modes for use on CRT terminals are speed dependent. At
speeds less than 1200 baud, the LCRTERA and LCRTKILL processing is
painfully slow, and stty(1) normally just sets LCRTBS and LCTLECH; at
speeds of 1200 baud or greater all of these bits are normally set.
Stty(1) summarizes these option settings and the use of the new
terminal driver as “newcrt.”
Output Processing
When one or more characters are written, they are actually transmitted
to the terminal as soon as previously-written characters have finished
typing. (As noted above, input characters are normally echoed by
putting them in the output queue as they arrive.) When a process
produces characters more rapidly than they can be typed, it will be
suspended when its output queue exceeds some limit. When the queue has
drained down to some threshold the program is resumed. Even parity is
generated on output if EVEN is specified (whether or not ODD is
specified). If only ODD is specified, odd parity is generated. Zero
parity is generated if neither EVEN nor ODD is specified. The EOT
character is not transmitted in cooked mode to prevent terminals that
respond to it from hanging up; programs using RAW or CBREAK mode should
be careful.
The terminal drivers provide necessary processing for cooked and CBREAK
mode output including delay generation for certain special characters
and parity generation. Delays are available after backspaces ^H, form
feeds ^L, carriage returns ^M, tabs ^I and newlines ^J. The driver
will also optionally expand tabs into spaces, where the tab stops are
assumed to be set every eight columns, and optionally convert newlines
to carriage returns followed by newline. These functions are
controlled by bits in the tty flags word; see Summary below.
The terminal drivers provide for mapping between uppercase and
lowercase on terminals lacking lowercase, and for other special
processing on deficient terminals.
Finally, in the new terminal driver, there is a output flush character,
normally ^O, which sets the LFLUSHO bit in the local mode word, causing
subsequent output to be flushed until it is cleared by a program or
more input is typed. This character has effect in both cooked and
CBREAK modes and causes pending input to be retyped if there is any
pending input. An ioctl to flush the characters in the input or output
queues, TIOCFLUSH, is also available.
Uppercase Terminals and Hazeltines
If the LCASE bit is set in the tty flags, then all upper-case letters
are mapped into the corresponding lower-case letter. The upper-case
letter may be generated by preceding it by `\'. Uppercase letters are
preceded by a `\' when output. In addition, the following escape
sequences can be generated on output and accepted on input:
for ` | ~ { }
use \´ \! \^ \( \)
To deal with Hazeltine terminals, which do not understand that ~ has
been made into an ASCII character, the LTILDE bit may be set in the
local mode word; in this case the character ~ will be replaced with the
character ` on output.
Flow Control
There are two characters (the stop character, normally ^S, and the
start character, normally ^Q) which cause output to be suspended and
resumed respectively. Extra stop characters typed when output is
already stopped have no effect, unless the start and stop characters
are made the same, in which case output resumes.
A bit in the flags word may be set to put the terminal into TANDEM
mode. In this mode the system produces a stop character (default ^S)
when the input queue is in danger of overflowing, and a start character
(default ^Q) when the input has drained sufficiently. This mode is
useful when the terminal is actually another machine that obeys those
conventions.
Hardware flow control is possible on NeXT 68040-based machines (see
zs(4)).
Line Control and Breaks
There are several ioctl calls available to control the state of the
terminal line. The TIOCSBRK ioctl will set the break bit in the
hardware interface causing a break condition to exist; this can be
cleared (usually after a delay with sleep(3)) by TIOCCBRK. Break
conditions in the input are reflected as a null character in RAW mode
or as the interrupt character in cooked or CBREAK mode. The TIOCCDTR
ioctl will clear the data terminal ready condition; it can be set again
by TIOCSDTR.
When the carrier signal from the dataset drops (usually because the
user has hung up his terminal) a SIGHUP hangup signal is sent to the
processes in the distinguished process group of the terminal; this
usually causes them to terminate. The SIGHUP can be suppressed by
setting the LNOHANG bit in the local state word of the driver. Access
to the terminal by other processes is then normally revoked, so any
further reads will fail, and programs that read a terminal and test for
end-of-file on their input will terminate appropriately.
It is possible to ask that the phone line be hung up on the last close
with the TIOCHPCL ioctl; this is normally done on the outgoing lines
and dialups.
Interrupt Characters
There are several characters that generate interrupts in cooked and
CBREAK mode; all are sent to the processes in the control group of the
terminal, as if a TIOCGPGRP ioctl were done to get the process group
and then a killpg(2) system call were done, except that these
characters also flush pending input and output when typed at a terminal
(a`'la TIOCFLUSH). The characters shown here are the defaults; the
field names in the structures (given below) are also shown. The
characters may be changed.
^C t_intrc (ETX) generates a SIGINT signal. This is the normal way
to stop a process which is no longer interesting, or to regain
control in an interactive program.
^\ t_quitc (FS) generates a SIGQUIT signal. This is used to cause
a program to terminate and produce a core image, if possible, in
the file core in the current directory.
^Z t_suspc (EM) generates a SIGTSTP signal, which is used to
suspend the current process group.
^Y t_dsuspc (SUB) generates a SIGTSTP signal as ^Z does, but the
signal is sent when a program attempts to read the ^Y, rather
than when it is typed.
Job Access Control
When using the new terminal driver, if a process which is not in the
distinguished process group of its control terminal attempts to read
from that terminal its process group is sent a SIGTTIN signal. This
signal normally causes the members of that process group to stop. If,
however, the process is ignoring SIGTTIN, has SIGTTIN blocked, or is in
the middle of process creation using vfork(2)), the read will return -1
and set errno to EIO.
When using the new terminal driver with the LTOSTOP bit set in the
local modes, a process is prohibited from writing on its control
terminal if it is not in the distinguished process group for that
terminal. Processes which are holding or ignoring SIGTTOU signals or
which are in the middle of a vfork(2) are excepted and allowed to
produce output. Terminal/window sizes. In order to accommodate
terminals and workstations with variable-sized windows, the terminal
driver provides a mechanism for obtaining and setting the current
terminal size. The driver does not use this information internally,
but only stores it and provides a uniform access mechanism. When the
size is changed, a SIGWINCH signal is sent to the terminal's process
group so that knowledgeable programs may detect size changes. This
facility was added in 4.3BSD and is not available in earlier versions
of the system.
Summary of Modes
Unfortunately, due to the evolution of the terminal driver, there are 4
different structures which contain various portions of the driver data.
The first of these (sgttyb) contains that part of the information
largely common between version 6 and version 7 UNIX systems. The
second contains additional control characters added in version 7. The
third is a word of local state added in 4BSD, and the fourth is another
structure of special characters added for the new driver. In the
future a single structure may be made available to programs which need
to access all this information; most programs need not concern
themselves with all this state.
Basic modes: sgtty.
The basic ioctls use the structure defined in <sgtty.h>:
struct sgttyb {
char sg_ispeed;
char sg_ospeed;
char sg_erase;
char sg_kill;
shortsg_flags;
};
The sg_ispeed and sg_ospeed fields describe the input and output speeds
of the device according to the following table, which corresponds to
the DEC DH-11 interface. If other hardware is used, impossible speed
changes are ignored. Symbolic values in the table are as defined in
<sgtty.h>.
B0 0 (hang up dataphone)
B50 1 50 baud
B75 2 75 baud
B110 3 110 baud
B134 4 134.5 baud
B150 5 150 baud
B200 6 200 baud
B300 7 300 baud
B600 8 600 baud
B1200 9 1200 baud
B1800 10 1800 baud
B2400 11 2400 baud
B4800 12 4800 baud
B9600 13 9600 baud
EXTA 14 19200 baud
EXTB 15 38400 baud
Note: 19200 and 38400 baud aren't reliable on 68030-based machines.
Code conversion and line control required for IBM 2741's (134.5 baud)
must be implemented by the user's program. The half-duplex line
discipline required for the 202 dataset (1200 baud) is not supplied;
full-duplex 212 datasets work fine.
The sg_erase and sg_kill fields of the argument structure specify the
erase and kill characters respectively. (Defaults are DELETE and ^U.)
The sg_flags field of the argument structure contains several bits that
determine the system's treatment of the terminal:
ALLDELAY 0177400 Delay algorithm selection
BSDELAY 0100000 Select backspace delays (not implemented):
BS0 0
BS1 0100000
VTDELAY 0040000 Select form-feed and vertical-tab delays:
FF0 0
FF1 0040000
CRDELAY 0030000 Select carriage-return delays:
CR0 0
CR1 0010000
CR2 0020000
CR3 0030000
TBDELAY 0006000 Select tab delays:
TAB0 0
TAB1 0002000
TAB2 0004000
XTABS 0006000
NLDELAY 0001400 Select new-line delays:
NL0 0
NL1 0000400
NL2 0001000
NL3 0001400
EVENP 0000200 Even parity allowed on input
ODDP 0000100 Odd parity allowed on input
RAW 0000040 Raw mode: wake up on all characters, 8-bit interface
CRMOD 0000020 Map CR into LF; output LF as CR-LF
ECHO 0000010 Echo (full duplex)
LCASE 0000004 Map uppercase to lowercase on input and lowercase to uppercase on
output
CBREAK 0000002 Return each character as soon as typed
TANDEM 0000001 Automatic flow control
The delay bits specify how long transmission stops to allow for
mechanical or other movement when certain characters are sent to the
terminal. In all cases a value of 0 indicates no delay.
Backspace delays are currently ignored but might be used for Terminet
300's.
If a form-feed/vertical tab delay is specified, it lasts for about 2
seconds.
Carriage-return delay type 1 lasts about .08 seconds and is suitable
for the Terminet 300. Delay type 2 lasts about .16 seconds and is
suitable for the VT05 and the TI 700. Delay type 3 is suitable for the
concept-100 and pads lines to be at least 9 characters at 9600 baud.
New-line delay type 1 is dependent on the current column and is tuned
for Teletype model 37's. Type 2 is useful for the VT05 and is about
.10 seconds. Type 3 is unimplemented and is 0.
Tab delay type 1 is dependent on the amount of movement and is tuned to
the Teletype model 37. Type 3, called XTABS, is not a delay at all but
causes tabs to be replaced by the appropriate number of spaces on
output.
The flags for even and odd parity control parity checking on input and
generation on output in cooked and CBREAK mode (unless LPASS8 or
LPASS8OUT is enabled, see below). Even parity is generated on output
if EVEN or both EVEN and ODD are specified. Odd parity is generated on
output if only ODD is specified. Zero parity is generated on output if
neither EVEN nor ODD is specified. Any parity is accepted on input if
both EVEN and ODD are specified or if neither is specified. If only
one of EVEN or ODD is specified, only that parity is accepted on input.
RAW disables all processing save output flushing with LFLUSHO; full 8
bits of input are given as soon as it is available; all 8 bits are
passed on output. A break condition in the input is reported as a null
character. If the input queue overflows in raw mode all data in the
input and output queues are discarded; this applies to both new and old
drivers.
CRMOD causes input carriage returns to be turned into new-lines, and
output and echoed new-lines to be output as a carriage return followed
by a line feed.
CBREAK is a sort of half-cooked (rare?) mode. Programs can read each
character as soon as typed, instead of waiting for a full line; all
processing is done except the input editing: character and word erase
and line kill, input reprint, and the special treatment of \ and EOT
are disabled.
TANDEM mode causes the system to produce a stop character (default ^S)
whenever the input queue is in danger of overflowing, and a start
character (default ^Q) when the input queue has drained sufficiently.
It is useful for flow control when the `terminal' is really another
computer which understands the conventions.
Note: The same ``stop'' and ``start'' characters are used for both
directions of flow control; the t_stopc character is accepted on input
as the character that stops output and is produced on output as the
character to stop input, and the t_startc character is accepted on
input as the character that restarts output and is produced on output
as the character to restart input.
Basic ioctls
A large number of ioctl(2) calls apply to terminals. Some have the
general form:
#include <sgtty.h>
ioctl(fildes, code, arg)
struct sgttyb *arg;
The applicable codes are:
TIOCGETP Fetch the basic parameters associated with the terminal,
and store in the pointed-to sgttyb structure.
TIOCSETP Set the parameters according to the pointed-to sgttyb
structure. The interface delays until output is
quiescent, then throws away any unread characters,
before changing the modes.
TIOCSETN Set the parameters like TIOCSETP but do not delay or
flush input. Input is not preserved, however, when
changing to or from RAW.
With the following codes arg is ignored.
TIOCEXCL Set “exclusive-use” mode: no further opens are permitted
until the file has been closed.
TIOCNXCL Turn off “exclusive-use” mode.
TIOCHPCL When the file is closed for the last time, hang up the
terminal. This is useful when the line is associated
with an ACU used to place outgoing calls.
With the following codes arg is a pointer to an int.
TIOCGETD arg is a pointer to an int into which is placed the
current line discipline number.
TIOCSETD arg is a pointer to an int whose value becomes the
current line discipline number.
TIOCFLUSH If the int pointed to by arg has a zero value, all
characters waiting in input or output queues are
flushed. Otherwise, the value of the int is for the
FREAD and FWRITE bits defined in <sys/file.h>; if the
FREAD bit is set, all characters waiting in input queues
are flushed, and if the FWRITE bit is set, all
characters waiting in output queues are flushed.
The remaining calls are not available in vanilla version 7 UNIX. In
cases where arguments are required, they are described; arg should
otherwise be given as 0.
TIOCSTI the argument points to a character which the system
pretends had been typed on the terminal.
TIOCSBRK the break bit is set in the terminal.
TIOCCBRK the break bit is cleared.
TIOCSDTR data terminal ready is set.
TIOCCDTR data terminal ready is cleared.
TIOCSTOP output is stopped as if the ``stop'' character had been
typed.
TIOCSTART output is restarted as if the ``start'' character had
been typed.
TIOCGPGRP arg is a pointer to an int into which is placed the
process group ID of the process group for which this
terminal is the control terminal.
TIOCSPGRP arg is a pointer to an int which is the value to which
the process group ID for this terminal will be set.
TIOCOUTQ returns in the int pointed to by arg the number of
characters queued for output to the terminal.
FIONREAD returns in the int pointed to by arg the number of
characters immediately readable from the argument
descriptor. This works for files, pipes, and terminals.
Tchars
The second structure associated with each terminal specifies characters
that are special in both the old and new terminal interfaces: The
following structure is defined in <sys/ioctl.h>, which is automatically
included in <sgtty.h>:
struct tchars {
char t_intrc; /* interrupt */
char t_quitc; /* quit */
char t_startc; /* start output */
char t_stopc; /* stop output */
char t_eofc; /* end-of-file */
char t_brkc; /* input delimiter (like nl) */
};
The default values for these characters are ^C, ^\, ^Q, ^S, ^D, and -1.
A character value of -1 eliminates the effect of that character. The
t_brkc character, by default -1, acts like a new-line in that it
terminates a `line,' is echoed, and is passed to the program. The
`stop' and `start' characters may be the same, to produce a toggle
effect. It is probably counterproductive to make other special
characters (including erase and kill) identical. The applicable ioctl
calls are:
TIOCGETC Get the special characters and put them in the specified
structure.
TIOCSETC Set the special characters to those given in the structure.
Local mode
The third structure associated with each terminal is a local mode word.
The bits of the local mode word are:
LCRTBS 000001 Backspace on erase rather than echoing erase
LPRTERA 000002 Printing terminal erase mode
LCRTERA 000004 Erase character echoes as backspace-space-backspace
LTILDE 000010 Convert ~ to ` on output (for Hazeltine terminals)
LMDMBUF 000020 Stop/start output when carrier drops
LLITOUT 000040 Suppress output translations
LTOSTOP 000100 Send SIGTTOU for background output
LFLUSHO 000200 Output is being flushed
LNOHANG 000400 Don't send hangup when carrier drops
LPASS8OUT 001000 Cooked mode with 8-bit output
(maintains tab expansion and newline to cr/lf mapping)
LCRTKIL 002000 BS-space-BS erase entire line on line kill
LPASS8 004000 Pass all 8 bits through on input, in any mode
LCTLECH 010000 Echo input control chars as ^X, delete as ^?
LPENDIN 020000 Retype pending input at next read or input character
LDECCTQ 040000 Only ^Q restarts output after ^S
LNOFLSH 100000 Inhibit flushing of pending I/O when an interrupt character is typed.
The applicable ioctl functions are:
TIOCLBIS arg is a pointer to an int whose value is a mask
containing the bits to be set in the local mode word.
TIOCLBIC arg is a pointer to an int whose value is a mask
containing the bits to be cleared in the local mode
word.
TIOCLSET arg is a pointer to an int whose value is stored in the
local mode word.
TIOCLGET arg is a pointer to an int into which the current local
mode word is placed.
Local special chars
The final control structure associated with each terminal is the
ltchars structure which defines control characters for the new terminal
driver. Its structure is:
struct ltchars {
char t_suspc; /* stop process signal */
char t_dsuspc; /* delayed stop process signal */
char t_rprntc; /* reprint line */
char t_flushc; /* flush output (toggles) */
char t_werasc; /* word erase */
char t_lnextc; /* literal next character */
};
The default values for these characters are ^Z, ^Y, ^R, ^O, ^W, and ^V.
A value of -1 disables the character.
The applicable ioctl functions are:
TIOCSLTC arg is a pointer to an ltchars structure which defines the
new local special characters.
TIOCGLTC arg is a pointer to an ltchars structure into which is
placed the current set of local special characters.
Window/terminal sizes
Each terminal has provision for storage of the current terminal or
window size in a winsize structure, with format:
struct winsize {
unsigned short ws_row; /* rows, in characters */
unsigned short ws_col; /* columns, in characters */
unsigned short ws_xpixel; /* horizontal size, pixels */
unsigned short ws_ypixel; /* vertical size, pixels */
};
A value of 0 in any field is interpreted as ``undefined;'' the entire
structure is zeroed on final close.
The applicable ioctl functions are:
TIOCGWINSZ
arg is a pointer to a struct winsize into which will be placed
the current terminal or window size information.
TIOCSWINSZ
arg is a pointer to a struct winsize which will be used to set
the current terminal or window size information. If the new
information is different than the old information, a SIGWINCH
signal will be sent to the terminal's process group.
FILES
/dev/tty
/dev/tty*
/dev/console
SEE ALSOcsh(1), stty(1), tset(1), ioctl(2), sigvec(2), stty(3C), getty(8),
zs(4)4th Berkeley Distribution May 19, 1986 TTY(4)
