NAME
stty —
set options for a terminal
device interface
SYNOPSIS
stty |
[-a | -e |
-g] [-f
file] [operand
...] |
DESCRIPTION
The
stty utility sets or reports on terminal characteristics
for the device that is its standard input. If no options or operands are
specified, it reports the settings of a subset of characteristics as well as
additional ones if they differ from their default values. Otherwise it
modifies the terminal state according to the specified arguments. Some
combinations of arguments are mutually exclusive on some terminal types.
The following options are available:
-
-
- -a
- Display all the current settings for the terminal to
standard output as per IEEE Std 1003.2
(“POSIX.2”).
-
-
- -e
- Display all the current settings for the terminal to
standard output in the traditional BSD
“all” and “everything” formats.
-
-
- -f
file
- Open and use the terminal named by
file rather than using standard input. The file is
opened using the
O_NONBLOCK
flag of
open(), making it possible to set or display settings on
a terminal that might otherwise block on the open.
-
-
- -g
- Display all the current settings for the terminal to
standard output in a form that may be used as an argument to a subsequent
invocation of stty to restore the current terminal state
as per IEEE Std 1003.2
(“POSIX.2”).
The following arguments are available to set the terminal characteristics:
Control Modes
Control mode flags affect hardware characteristics associated with the terminal.
This corresponds to the
c_cflag of the
termios(4) structure.
-
-
- parenb
(-parenb)
- Enable (disable) parity generation and detection.
-
-
- parodd
(-parodd)
- Select odd (even) parity.
-
-
- cs5 cs6 cs7
cs8
- Select character size, if possible.
-
-
- number
- Set terminal baud rate to number, if
possible. If the baud rate is set to zero, modem control is no longer
asserted.
-
-
- ispeed
number
- Set terminal input baud rate to
number, if possible. If the input baud rate is set
to zero, the input baud rate is set to the value of the output baud
rate.
-
-
- ospeed
number
- Set terminal output baud rate to
number, if possible. If the output baud rate is set
to zero, modem control is no longer asserted.
-
-
- speed
number
- This sets both ispeed and
ospeed to number.
-
-
- hupcl
(-hupcl)
- Stop asserting modem control (do not stop asserting modem
control) on last close.
-
-
- hup
(-hup)
- Same as hupcl (-hupcl).
-
-
- cstopb
(-cstopb)
- Use two (one) stop bits per character.
-
-
- cread
(-cread)
- Enable (disable) the receiver.
-
-
- clocal
(-clocal)
- Assume a line without (with) modem control.
-
-
- crtscts
(-crtscts)
- Enable RTS/CTS flow control.
-
-
- cdtrcts
(-cdtrcts)
- Enable DTR/CTS flow control (if supported).
This corresponds to the
c_iflag of the
termios(4) structure.
-
-
- ignbrk
(-ignbrk)
- Ignore (do not ignore) break on input.
-
-
- brkint
(-brkint)
- Signal (do not signal)
INTR
on
break.
-
-
- ignpar
(-ignpar)
- Ignore (do not ignore) parity errors.
-
-
- parmrk
(-parmrk)
- Mark (do not mark) parity errors.
-
-
- inpck
(-inpck)
- Enable (disable) input parity checking.
-
-
- istrip
(-istrip)
- Strip (do not strip) input characters to seven bits.
-
-
- inlcr
(-inlcr)
- Map (do not map)
NL
to
CR
on input.
-
-
- igncr
(-igncr)
- Ignore (do not ignore)
CR
on
input.
-
-
- icrnl
(-icrnl)
- Map (do not map)
CR
to
NL
on input.
-
-
- ixon
(-ixon)
- Enable (disable)
START/STOP
output
control. Output from the system is stopped when the system receives
STOP
and started when the system receives
START
, or if ixany is set, any
character restarts output.
-
-
- ixoff
(-ixoff)
- Request that the system send (not send)
START/STOP
characters when the input queue is
nearly empty/full.
-
-
- ixany
(-ixany)
- Allow any character (allow only
START
) to restart output.
-
-
- imaxbel
(-imaxbel)
- The system imposes a limit of
MAX_INPUT
(currently 255) characters in the input
queue. If imaxbel is set and the input queue limit has
been reached, subsequent input causes the system to send an ASCII BEL
character to the output queue (the terminal beeps at you). Otherwise, if
imaxbel is unset and the input queue is full, the next
input character causes the entire input and output queues to be
discarded.
Output Modes
This corresponds to the
c_oflag of the
termios(4) structure.
-
-
- opost
(-opost)
- Post-process output (do not post-process output; ignore all
other output modes).
-
-
- onlcr
(-onlcr)
- Map (do not map)
NL
to
CR-NL
on output.
-
-
- ocrnl
(-ocrnl)
- Map (do not map)
CR
to
NL
on output.
-
-
- oxtabs
(-oxtabs)
- Expand (do not expand) tabs to spaces on output.
-
-
- onocr
(-onocr)
- Do not (do) output CRs at column zero.
-
-
- onlret
(-onlret)
- On the terminal NL performs (does not perform) the CR
function.
Local Modes
Local mode flags (lflags) affect various and sundry characteristics of terminal
processing. Historically the term "local" pertained to new job
control features implemented by Jim Kulp on a PDP-11/70 at IIASA. Later the
driver ran on the first VAX at Evans Hall, UC Berkeley, where the job control
details were greatly modified but the structure definitions and names remained
essentially unchanged. The second interpretation of the ‘l’ in
lflag is “line discipline flag”, which corresponds to the
c_lflag of the
termios(4) structure.
-
-
- isig
(-isig)
- Enable (disable) the checking of characters against the
special control characters
INTR
,
QUIT
, and SUSP
.
-
-
- icanon
(-icanon)
- Enable (disable) canonical input
(
ERASE
and KILL
processing).
-
-
- iexten
(-iexten)
- Enable (disable) any implementation defined special control
characters not currently controlled by icanon, isig, or ixon.
-
-
- echo
(-echo)
- Echo back (do not echo back) every character typed.
-
-
- echoe
(-echoe)
- The
ERASE
character shall (shall
not) visually erase the last character in the current line from the
display, if possible.
-
-
- echok
(-echok)
- Echo (do not echo)
NL
after
KILL
character.
-
-
- echoke
(-echoke)
- The
KILL
character shall (shall
not) visually erase the current line from the display, if possible.
-
-
- echonl
(-echonl)
- Echo (do not echo)
NL
, even if echo
is disabled.
-
-
- echoctl
(-echoctl)
- If echoctl is set, echo control
characters as ^X. Otherwise control characters echo as themselves.
-
-
- echoprt
(-echoprt)
- For printing terminals. If set, echo erased characters
backwards within “\” and “/”. Otherwise, disable
this feature.
-
-
- noflsh
(-noflsh)
- Disable (enable) flush after
INTR
,
QUIT
, SUSP
.
-
-
- tostop
(-tostop)
- Send (do not send)
SIGTTOU
for
background output. This causes background jobs to stop if they attempt
terminal output.
-
-
- altwerase
(-altwerase)
- Use (do not use) an alternative word erase algorithm when
processing
WERASE
characters. This alternative
algorithm considers sequences of alphanumeric/underscores as words. It
also skips the first preceding character in its classification (as a
convenience since the one preceding character could have been erased with
simply an ERASE
character).
-
-
- mdmbuf
(-mdmbuf)
- If set, flow control output based on condition of Carrier
Detect. Otherwise writes return an error if Carrier Detect is low (and
Carrier is not being ignored with the
CLOCAL
flag).
-
-
- flusho
(-flusho)
- Indicates output is (is not) being discarded.
-
-
- pendin
(-pendin)
- Indicates input is (is not) pending after a switch from
non-canonical to canonical mode and will be re-input when a read becomes
pending or more input arrives.
Control Characters
-
-
- control-character
string
- Set control-character to string
string. If the string is a single character, then
the control character is set to that character. If the string is the two
character sequence "^-" or the string "undef", then
the control character is disabled (i.e., set to
{
_POSIX_VDISABLE
}).
Recognized control characters:
control- |
|
|
character |
Subscript |
Description |
_________ |
_________ |
_______________ |
eof |
VEOF |
EOF character |
eol |
VEOL |
EOL character |
eol2 |
VEOL2 |
EOL2 character |
erase |
VERASE |
ERASE character |
werase |
VWERASE |
WERASE character |
kill |
VKILL |
KILL character |
reprint |
VREPRINT |
REPRINT character |
intr |
VINTR |
INTR character |
quit |
VQUIT |
QUIT character |
susp |
VSUSP |
SUSP character |
dsusp |
VDSUSP |
DSUSP character |
start |
VSTART |
START character |
stop |
VSTOP |
STOP character |
lnext |
VLNEXT |
LNEXT character |
status |
VSTATUS |
STATUS character |
discard |
VDISCARD |
DISCARD character |
-
-
- min
number
-
- time
number
- Set the value of min or time to
number.
MIN
and
TIME
are used in Non-Canonical mode input
processing (-icanon).
Combination Modes
-
-
- saved
settings
- Set the current terminal characteristics to the saved
settings produced by the -g option.
-
-
- evenp
or parity
- Enable parenb and cs7; disable parodd.
-
-
- oddp
- Enable parenb, cs7, and parodd.
-
-
- -parity,
-evenp, -oddp
- Disable parenb, and set cs8.
-
-
- nl
(-nl)
- Enable (disable) icrnl. In addition -nl unsets inlcr and
igncr.
-
-
- ek
- Reset
ERASE
and
KILL
characters back to system defaults.
-
-
- sane
- Resets all modes to reasonable values for interactive
terminal use.
-
-
- insane
- Sets all modes to random values, which are very likely (but
not guaranteed) to be unreasonable for interactive terminal use.
-
-
- tty
- Set the line discipline to the standard terminal line
discipline
TTYDISC
.
-
-
- crt
(-crt)
- Set (disable) all modes suitable for a CRT display
device.
-
-
- kerninfo
(-kerninfo)
- Enable (disable) the system generated status line
associated with processing a
STATUS
character
(usually set to ^T). The status line consists of the system load average,
the current command name, its process ID, the event the process is waiting
on (or the status of the process), the user and system times, percent CPU,
and current memory usage.
-
-
- columns
number
- The terminal size is recorded as having
number columns.
-
-
- cols
number
- An alias for columns.
-
-
- rows
number
- The terminal size is recorded as having
number rows.
-
-
- dec
- Set modes suitable for users of Digital Equipment
Corporation systems (
ERASE
,
KILL
, and INTR
characters
are set to ^?, ^U, and ^C; ixany
is disabled, and
crt
is enabled).
-
-
- extproc
(-extproc)
- If set, this flag indicates that some amount of terminal
processing is being performed by either the terminal hardware or by the
remote side connected to a pty.
-
-
- raw
(-raw)
- If set, change the modes of the terminal so that no input
or output processing is performed. If unset, change the modes of the
terminal to some reasonable state that performs input and output
processing. Note that since the terminal driver no longer has a single
RAW
bit, it is not possible to intuit what flags
were set prior to setting raw. This means that unsetting
raw may not put back all the setting that were
previously in effect. To set the terminal into a raw state and then
accurately restore it, the following shell code is recommended:
save_state=$(stty -g)
stty raw
...
stty "$save_state"
-
-
- size
- The size of the terminal is printed as two numbers on a
single line, first rows, then columns.
Compatibility Modes
These modes remain for compatibility with the previous version of the
stty utility.
-
-
- all
- Reports all the terminal modes as with
stty -a except that the control
characters are printed in a columnar format.
-
-
- everything
- Same as all.
-
-
- cooked
- Same as sane.
-
-
- cbreak
- If set, enables brkint,
ixon, imaxbel,
opost, isig, iexten,
and -icanon. If unset, same as
sane.
-
-
- new
- Same as tty.
-
-
- old
- Same as tty.
-
-
- newcrt
(-newcrt)
- Same as crt.
-
-
- pass8
- The converse of parity.
-
-
- tandem
(-tandem)
- Same as ixoff.
-
-
- decctlq
(-decctlq)
- The converse of ixany.
-
-
- crterase
(-crterase)
- Same as echoe.
-
-
- crtbs
(-crtbs)
- Same as echoe.
-
-
- crtkill
(-crtkill)
- Same as echoke.
-
-
- ctlecho
(-ctlecho)
- Same as echoctl.
-
-
- prterase
(-prterase)
- Same as echoprt.
-
-
- litout
(-litout)
- The converse of opost.
-
-
- tabs
(-tabs)
- The converse of oxtabs.
-
-
- brk
value
- Same as the control character eol.
-
-
- flush
value
- Same as the control character
discard.
-
-
- rprnt
value
- Same as the control character
reprint.
Control operations
These operations are not modes, but rather commands to be performed by the tty
layer.
-
-
- ostart
- Performs a "start output" operation, as normally
done by an incoming START character when ixon is
set.
-
-
- ostop
- Performs a "stop output" operation, as normally
done by an incoming STOP character when ixon is
set.
EXIT STATUS
The
stty utility exits 0 on success, and >0 if an
error occurs.
SEE ALSO
termios(4),
tty(4)
STANDARDS
The
stty utility is expected to be
IEEE Std
1003.2 (“POSIX.2”) compatible. The
-e and
-f flags are extensions to the standard, as are the operands
mentioned in the control operations section.
HISTORY
An
stty utility appeared in
Version 2
AT&T UNIX.