STTY(1) - General Commands Manual #
STTY(1) - General Commands Manual
NAME #
stty - set the options for a terminal device interface
SYNOPSIS #
stty [-a | -e | -g] [-f file] [operands]
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 options are as follows:
-a
Display all the current settings for the terminal to standard output.
-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(2), 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. The output does not contain any characters that require quoting, to avoid word expansion by the shell.
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
in the termios 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 the number given, if possible. If the baud rate is set to zero, modem control is no longer asserted.
ispeed number
Set terminal input baud rate to the number given, 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 the number given, 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 (disable) RTS/CTS flow control.
Input modes #
This corresponds to the
c_iflag
in the termios 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
toCR
on input.
igncr (-igncr)
Ignore (do not ignore)
CR
on input.
icrnl (-icrnl)
Map (do not map)
CR
toNL
on input.
iuclc (-iuclc)
Translate (do not translate) upper case to lower case on input.
ixon (-ixon)
Enable (disable)
START/STOP
output control. Output from the system is stopped when the system receivesSTOP
and started when the system receivesSTART
, 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 structure.
opost (-opost)
Post-process output (do not post-process output; ignore all other output modes).
onlcr (-onlcr)
Map (do not map)
NL
toCR-NL
on output.
ocrnl (-ocrnl)
Translate (do not translate) carriage return to newline on output.
onocr (-onocr)
Carriage return is not output (is output) at column 0.
onlret (-onlret)
Newline performs (does not perform) carriage return on output.
olcuc (-olcuc)
Translate (do not translate) lower case to upper case on output.
oxtabs (-oxtabs)
Expand (do not expand) tabs to spaces on output.
onoeot (-onoeot)
Discard (do not discard) EOFs on output.
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 structure.
isig (-isig)
Enable (disable) the checking of characters against the special control characters
INTR
,QUIT
, andSUSP
.
icanon (-icanon)
Enable (disable) canonical input (
ERASE
andKILL
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
afterKILL
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 alternate word erase algorithm when processing
`WERASE`
characters.
This alternate 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.
xcase (-xcase)
Upper and lower case is (is not) handled canonically on input and output
with
**iuclc**
and
**olcuc**.
Control characters #
control-character string
Set
*control-character*
to
*string*.
If string is a single character,
the control character is set to
that character.
If string is the
two character sequence
'`^-`'
or the string
"undef",
the control character
is disabled (i.e. set to
{`_POSIX_VDISABLE`}).
Recognized control-characters:
> **Control** **Subscript** **Description**
> **character**
> eof `VEOF` EOF character
> eol `VEOL` EOL character
> eol2 `VEOL2` EOL2 character
> erase `VERASE` ERASE character
> werase `VWERASE` WERASE character
> intr `VINTR` INTR character
> kill `VKILL` KILL character
> quit `VQUIT` QUIT character
> susp `VSUSP` SUSP character
> start `VSTART` START character
> stop `VSTOP` STOP character
> dsusp `VDSUSP` DSUSP character
> lnext `VLNEXT` LNEXT character
> reprint `VREPRINT` REPRINT character
> status `VSTATUS` STATUS 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.
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
This is 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 command.
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**.
lcase (-lcase)
Same as
**iuclc**,
**olcuc**
and
**xcase**.
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 exits0 on success, and>0 if an error occurs.
SEE ALSO #
STANDARDS #
The stty utility is compliant with the IEEE Std 1003.1-2008 (“POSIX.1”) specification.
The flags [-ef], the operands altwerase, cols, columns, crt, crtscts, dec, echoke, extproc, flusho, imaxbel, kerninfo, mdmbuf, onlcr, onoeot, ostart, ostop, oxtabs, pendin, rows, size, speed, and tty, and the control characters eol2, dsusp, lnext, reprint, status, and werase are all extensions to that specification.
The operands iuclc, olcuc, and xcase are marked by IEEE Std 1003.1-2008 (“POSIX.1”) as legacy items; the operands listed in Compatibility modes can also be considered legacy.
The operands bs0-1, cr0-3, ff0-1, nl0-1, ocrnl, ofdel, ofill, onlret, onocr, raw, tab0-3, tabs, and vt0-1 are marked by IEEE Std 1003.1-2008 (“POSIX.1”) as being an X/Open System Interfaces option. Of those, only ocrnl, onlret, onocr, raw, and tabs are supported by this implementation of stty, and behaviour for tabs differs.
HISTORY #
A stty command appeared in Version2 AT&T UNIX.
OpenBSD 7.5 - March 31, 2022