STTY(1) - General Commands Manual

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 to CR on input.

igncr (-igncr)

Ignore (do not ignore) CR on input.

icrnl (-icrnl)

Map (do not map) CR to NL 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 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 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)

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, 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 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 #

termios(4), tty(4)

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