stty
—
set options for a terminal device interface
stty |
[-a | -e |
-g ] [-f
file] [operand ...] |
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 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.
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 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-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).
- 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.
cols
number
- The terminal size is recorded as having number
columns.
columns
number
- An alias for
cols
.
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.
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
.
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.
The stty
utility exits 0 on success,
and >0 if an error occurs.
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.
An stty
utility appeared in
Version 2 AT&T UNIX.