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The Open Group Base Specifications Issue 7, 2018 edition
IEEE Std 1003.1-2017 (Revision of IEEE Std 1003.1-2008)
Copyright © 2001-2018 IEEE and The Open Group
A newer edition of this document exists
here
NAME
stty - set the options for a terminal
SYNOPSIS
stty
-a|-g
stty
operand
...
DESCRIPTION
The
stty
utility shall set or report on terminal I/O characteristics for the device that is its standard input. Without
options or operands specified, it shall report the settings of certain characteristics, usually those that differ from
implementation-defined defaults. Otherwise, it shall modify the terminal state according to the specified operands. Detailed
information about the modes listed in the first five groups below are described in XBD
General Terminal Interface
. Operands in the Combination Modes group (see
Combination Modes
) are implemented using operands in the previous groups. Some combinations of operands
are mutually-exclusive on some terminal types; the results of using such combinations are unspecified.
Typical implementations of this utility require a communications line configured to use the
termios
interface defined in
the System Interfaces volume of POSIX.1-2017. On systems where none of these lines are available, and on lines not currently
configured to support the
termios
interface, some of the operands need not affect terminal characteristics.
OPTIONS
The
stty
utility shall conform to XBD
Utility Syntax Guidelines
The following options shall be supported:
-a
Write to standard output all the current settings for the terminal.
-g
Write to standard output all the current settings in an unspecified form that can be used as arguments to another invocation of
the
stty
utility on the same system. The form used shall not contain any characters that would require quoting to avoid word
expansion by the shell; see
wordexp
OPERANDS
The following operands shall be supported to set the terminal characteristics.
Control Modes
parenb
-parenb
Enable (disable) parity generation and detection. This shall have the effect of setting (not setting) PARENB in the
termios
c_cflag
field, as defined in XBD
General Terminal
Interface
parodd
-parodd
Select odd (even) parity. This shall have the effect of setting (not setting) PARODD in the
termios
c_cflag
field, as
defined in XBD
General Terminal Interface
cs5 cs6 cs7 cs8
Select character size, if possible. This shall have the effect of setting CS5, CS6, CS7, and CS8, respectively, in the
termios
c_cflag
field, as defined in XBD
General Terminal
Interface
number
Set terminal baud rate to the number given, if possible. If the baud rate is set to zero, the modem control lines shall no
longer be asserted. This shall have the effect of setting the input and output
termios
baud rate values as defined in XBD
General Terminal Interface
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 shall
be specified by the value of the output baud rate. This shall have the effect of setting the input
termios
baud rate values
as defined in XBD
General Terminal Interface
ospeed
number
Set terminal output baud rate to the number given, if possible. If the output baud rate is set to zero, the modem control lines
shall no longer be asserted. This shall have the effect of setting the output
termios
baud rate values as defined in XBD
General Terminal Interface
hupcl
-hupcl
Stop asserting modem control lines (do not stop asserting modem control lines) on last close. This shall have the effect of
setting (not setting) HUPCL in the
termios
c_cflag
field, as defined in XBD
General Terminal Interface
hup
-hup
Equivalent to
hupcl
-hupcl
).
cstopb
-cstopb
Use two (one) stop bits per character. This shall have the effect of setting (not setting) CSTOPB in the
termios
c_cflag
field, as defined in XBD
General Terminal Interface
cread
-cread
Enable (disable) the receiver. This shall have the effect of setting (not setting) CREAD in the
termios
c_cflag
field, as defined in XBD
General Terminal Interface
clocal
-clocal
Assume a line without (with) modem control. This shall have the effect of setting (not setting) CLOCAL in the
termios
c_cflag
field, as defined in XBD
General Terminal Interface
It is unspecified whether
stty
shall report an error if an attempt to set a Control Mode fails.
Input Modes
ignbrk
-ignbrk
Ignore (do not ignore) break on input. This shall have the effect of setting (not setting) IGNBRK in the
termios
c_iflag
field, as defined in XBD
General Terminal Interface
brkint
-brkint
Signal (do not signal) INTR on break. This shall have the effect of setting (not setting) BRKINT in the
termios
c_iflag
field, as defined in XBD
General Terminal Interface
ignpar
-ignpar
Ignore (do not ignore) bytes with parity errors. This shall have the effect of setting (not setting) IGNPAR in the
termios
c_iflag
field, as defined in XBD
General Terminal
Interface
parmrk
-parmrk
Mark (do not mark) parity errors. This shall have the effect of setting (not setting) PARMRK in the
termios
c_iflag
field, as defined in XBD
General Terminal Interface
inpck
-inpck
Enable (disable) input parity checking. This shall have the effect of setting (not setting) INPCK in the
termios
c_iflag
field, as defined in XBD
General Terminal Interface
istrip
-istrip
Strip (do not strip) input characters to seven bits. This shall have the effect of setting (not setting) ISTRIP in the
termios
c_iflag
field, as defined in XBD
General Terminal
Interface
inlcr
-inlcr
Map (do not map) NL to CR on input. This shall have the effect of setting (not setting) INLCR in the
termios
c_iflag
field, as defined in XBD
General Terminal Interface
igncr (-igncr)
Ignore (do not ignore) CR on input. This shall have the effect of setting (not setting) IGNCR in the
termios
c_iflag
field, as defined in XBD
General Terminal Interface
icrnl
-icrnl
Map (do not map) CR to NL on input. This shall have the effect of setting (not setting) ICRNL in the
termios
c_iflag
field, as defined in XBD
General Terminal Interface
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. This shall have the effect of setting (not setting) IXON in the
termios
c_iflag
field, as
defined in XBD
General Terminal Interface
ixany
-ixany
Allow any character to restart output. This shall have the effect of setting (not setting) IXANY in the
termios
c_iflag
field, as defined in XBD
General Terminal Interface
ixoff
-ixoff
Request that the system send (not send) STOP characters when the input queue is nearly full and START characters to resume data
transmission. This shall have the effect of setting (not setting) IXOFF in the
termios
c_iflag
field, as defined in
XBD
General Terminal Interface
Output Modes
opost
-opost
Post-process output (do not post-process output; ignore all other output modes). This shall have the effect of setting (not
setting) OPOST in the
termios
c_oflag
field, as defined in XBD
General
Terminal Interface
onlcr
-onlcr
XSI
Map (do not map) NL to CR-NL on output. This shall have the effect of setting (not setting) ONLCR in the
termios
c_oflag
field, as defined in XBD
General Terminal Interface
ocrnl
-ocrnl
XSI
Map (do not map) CR to NL on output. This shall have the effect of setting (not setting) OCRNL in the
termios
c_oflag
field, as defined in XBD
General Terminal Interface
onocr
-onocr
XSI
Do not (do) output CR at column zero. This shall have the effect of setting (not setting) ONOCR in the
termios
c_oflag
field, as defined in XBD
General Terminal Interface
onlret
-onlret
XSI
The terminal newline key performs (does not perform) the CR function. This shall have the effect of setting (not setting) ONLRET in
the
termios
c_oflag
field, as defined in XBD
General Terminal
Interface
ofill
-ofill
XSI
Use fill characters (use timing) for delays. This shall have the effect of setting (not setting) OFILL in the
termios
c_oflag
field, as defined in XBD
General Terminal Interface
ofdel
-ofdel
XSI
Fill characters are DELs (NULs). This shall have the effect of setting (not setting) OFDEL in the
termios
c_oflag
field, as defined in XBD
General Terminal Interface
cr0 cr1 cr2 cr3
XSI
Select the style of delay for CRs. This shall have the effect of setting CRDLY to CR0, CR1, CR2, or CR3, respectively, in the
termios
c_oflag
field, as defined in XBD
General Terminal
Interface
nl0 nl1
XSI
Select the style of delay for NL. This shall have the effect of setting NLDLY to NL0 or NL1, respectively, in the
termios
c_oflag
field, as defined in XBD
General Terminal Interface
tab0 tab1 tab2 tab3
XSI
Select the style of delay for horizontal tabs. This shall have the effect of setting TABDLY to TAB0, TAB1, TAB2, or TAB3,
respectively, in the
termios
c_oflag
field, as defined in XBD
General
Terminal Interface
. Note that TAB3 has the effect of expanding
tabs
-tabs
XSI
Synonym for
tab0
tab3
).
bs0 bs1
XSI
Select the style of delay for
respectively, in the
termios
c_oflag
field, as defined in XBD
General
Terminal Interface
ff0 ff1
XSI
Select the style of delay for
respectively, in the
termios
c_oflag
field, as defined in XBD
General
Terminal Interface
vt0 vt1
XSI
Select the style of delay for
respectively, in the
termios
c_oflag
field, as defined in XBD
General
Terminal Interface
Local Modes
isig
-isig
Enable (disable) the checking of characters against the special control characters INTR, QUIT, and SUSP. This shall have the
effect of setting (not setting) ISIG in the
termios
c_lflag
field, as defined in XBD
General Terminal Interface
icanon
-icanon
Enable (disable) canonical input (ERASE and KILL processing). This shall have the effect of setting (not setting) ICANON in the
termios
c_lflag
field, as defined in XBD
General Terminal
Interface
iexten
-iexten
Enable (disable) any implementation-defined special control characters not currently controlled by
icanon
isig
ixon
, or
ixoff
. This shall have the effect of setting (not setting) IEXTEN in the
termios
c_lflag
field, as defined in XBD
General Terminal Interface
echo
-echo
Echo back (do not echo back) every character typed. This shall have the effect of setting (not setting) ECHO in the
termios
c_lflag
field, as defined in XBD
General Terminal
Interface
echoe
-echoe
The ERASE character visually erases (does not erase) the last character in the current line from the display, if possible. This
shall have the effect of setting (not setting) ECHOE in the
termios
c_lflag
field, as defined in XBD
General Terminal Interface
echok
-echok
Echo (do not echo) NL after KILL character. This shall have the effect of setting (not setting) ECHOK in the
termios
c_lflag
field, as defined in XBD
General Terminal Interface
echonl
-echonl
Echo (do not echo) NL, even if
echo
is disabled. This shall have the effect of setting (not setting) ECHONL in the
termios
c_lflag
field, as defined in XBD
General Terminal
Interface
noflsh
-noflsh
Disable (enable) flush after INTR, QUIT, SUSP. This shall have the effect of setting (not setting) NOFLSH in the
termios
c_lflag
field, as defined in XBD
General Terminal Interface
tostop
-tostop
Send SIGTTOU for background output. This shall have the effect of setting (not setting) TOSTOP in the
termios
c_lflag
field, as defined in XBD
General Terminal Interface
Special Control Character Assignments
control
>-
character string
Set <
control
>-
character
to
string
. If <
control
>-
character
is one of the character
sequences in the first column of the following table, the corresponding XBD
General
Terminal Interface
control character from the second column shall be recognized. This has the effect of setting the
corresponding element of the
termios
c_cc
array (see XBD
Headers
).
Table: Control Character Names in
stty
Control Character
c_cc Subscript
Description
eof
VEOF
EOF character
eol
VEOL
EOL character
erase
VERASE
ERASE 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
If
string
is a single character, the control character shall be set to that character. If
string
is the
two-character sequence
"^-"
or the string
undef
, the control character shall be set to _POSIX_VDISABLE, if it is
in effect for the device; if _POSIX_VDISABLE is not in effect for the device, it shall be treated as an error. In the POSIX locale,
if
string
is a two-character sequence beginning with
'^'
), and the second character is one of
those listed in the
"^c"
column of the following table, the control character shall be set to the corresponding character
value in the Value column of the table.
Table: Circumflex Control Characters in
stty
^c
Value
^c
Value
^c
Value
a, A
l, L
w, W
b, B
m, M
x, X
c, C
n, N
y, Y
d, D
o, O
z, Z
e, E
p, P
f, F
q, Q
g, G
r, R
h, H
s, S
i, I
t, T
j, J
u, U
k, K
v, V
min
number
Set the value of MIN to
number
. MIN is used in non-canonical mode input processing (
icanon
).
time
number
Set the value of TIME to
number
. TIME is 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
, or
-oddp
Disable
parenb
, and set
cs8
raw
-raw
or
cooked
XSI
Enable (disable) raw input and output. Raw mode shall be equivalent to setting:
stty cs8 erase ^- kill ^- intr ^- \
quit ^- eof ^- eol ^- -post -inpck
nl
-nl
Disable (enable)
icrnl
. In addition,
-nl
unsets
inlcr
and
igncr
ek
Reset ERASE and KILL characters back to system defaults.
sane
Reset all modes to some reasonable, unspecified, values.
STDIN
Although no input is read from standard input, standard input shall be used to get the current terminal I/O characteristics and
to set new terminal I/O characteristics.
INPUT FILES
None.
ENVIRONMENT VARIABLES
The following environment variables shall affect the execution of
stty
LANG
Provide a default value for the internationalization variables that are unset or null. (See XBD
Internationalization Variables
for the precedence of internationalization
variables used to determine the values of locale categories.)
LC_ALL
If set to a non-empty string value, override the values of all the other internationalization variables.
LC_CTYPE
This variable determines the locale for the interpretation of sequences of bytes of text data as characters (for example,
single-byte as opposed to multi-byte characters in arguments) and which characters are in the class
LC_MESSAGES
Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error.
NLSPATH
XSI
Determine the location of message catalogs for the processing of
LC_MESSAGES.
ASYNCHRONOUS EVENTS
Default.
STDOUT
If operands are specified, no output shall be produced.
If the
-g
option is specified,
stty
shall write to standard output the current settings in a form that can be used
as arguments to another instance of
stty
on the same system.
If the
-a
option is specified, all of the information as described in the OPERANDS section shall be written to standard
output. Unless otherwise specified, this information shall be written as
on one or more lines, with an unspecified number of tokens per line. Additional information may be written.
If no options or operands are specified, an unspecified subset of the information written for the
-a
option shall be
written.
If speed information is written as part of the default output, or if the
-a
option is specified and if the terminal input
speed and output speed are the same, the speed information shall be written as follows:
"speed %d baud;", <
speed
Otherwise, speeds shall be written as:
"ispeed %d baud; ospeed %d baud;", <
ispeed
>, <
ospeed
In locales other than the POSIX locale, the word
baud
may be changed to something more appropriate in those locales.
If control characters are written as part of the default output, or if the
-a
option is specified, control characters
shall be written as:
"%s = %s;", <
control-character name
>, <
value
where <
value
> is either the character, or some visual representation of the character if it is non-printable, or
the string
undef
if the character is disabled.
STDERR
The standard error shall be used only for diagnostic messages.
OUTPUT FILES
None.
EXTENDED DESCRIPTION
None.
EXIT STATUS
The following exit values shall be returned:
The terminal options were read or set successfully.
>0
An error occurred.
CONSEQUENCES OF ERRORS
Default.
The following sections are informative.
APPLICATION USAGE
The
-g
flag is designed to facilitate the saving and restoring of terminal state from the shell level. For example, a
program may:
saveterm="$(stty -g)" # save terminal state
stty
(new settings)
# set new state
... # ...
stty $saveterm # restore terminal state
Since the format is unspecified, the saved value is not portable across systems.
Since the
-a
format is so loosely specified, scripts that save and restore terminal settings should use the
-g
option.
EXAMPLES
None.
RATIONALE
The original
stty
description was taken directly from System V and reflected the System V terminal driver
termio
It has been modified to correspond to the terminal driver
termios
Output modes are specified only for XSI-conformant systems. All implementations are expected to provide
stty
operands
corresponding to all of the output modes they support.
The
stty
utility is primarily used to tailor the user interface of the terminal, such as selecting the preferred ERASE
and KILL characters. As an application programming utility,
stty
can be used within shell scripts to alter the terminal
settings for the duration of the script.
The
termios
section states that individual disabling of control characters is possible through the option
_POSIX_VDISABLE. If enabled, two conventions currently exist for specifying this: System V uses
"^-"
, and BSD uses
undef
. Both are accepted by
stty
in this volume of POSIX.1-2017. The other BSD convention of using the letter
'u'
was rejected because it conflicts with the actual letter
'u'
, which is an acceptable value for a control
character.
Early proposals did not specify the mapping of
"^c"
to control characters because the control characters were not
specified in the POSIX locale character set description file requirements. The control character set is now specified in XBD
Definitions
, so the historical mapping is specified. Note that although the
mapping corresponds to control-character key assignments on many terminals that use the ISO/IEC 646:1991 standard (or ASCII)
character encodings, the mapping specified here is to the control characters, not their keyboard encodings.
Since
termios
supports separate speeds for input and output, two new options were added to specify each distinctly.
Some historical implementations use standard input to get and set terminal characteristics; others use standard output. Since
input from a login TTY is usually restricted to the owner while output to a TTY is frequently open to anyone, using standard input
provides fewer chances of accidentally (or maliciously) altering the terminal settings of other users. Using standard input also
allows
stty
-a
and
stty
-g
output to be redirected for later use. Therefore, usage of standard input is
required by this volume of POSIX.1-2017.
FUTURE DIRECTIONS
None.
SEE ALSO
Shell Command Language
XBD
Environment Variables
General Terminal Interface
Utility Syntax Guidelines
CHANGE HISTORY
First released in Issue 2.
Issue 5
The description of
tabs
is clarified.
The FUTURE DIRECTIONS section is added.
Issue 6
The LEGACY items
iuclc
(-
iuclc
),
xcase
olcuc
(-
olcuc
),
lcase
(-
lcase
), and
LCASE
(-
LCASE
) are removed.
IEEE Std 1003.1-2001/Cor 1-2002, item XCU/TC1/D6/37 is applied, applying IEEE PASC Interpretation 1003.2 #133,
fixing an error in the OPERANDS section for the Combination Modes
nl
-nl
).
Issue 7
Austin Group Interpretation 1003.1-2001 #144 is applied, moving functionality relating to the IXANY symbol from the XSI option
to the Base.
SD5-XCU-ERN-97 is applied, updating the SYNOPSIS.
POSIX.1-2008, Technical Corrigendum 2, XCU/TC2-2008/0189 [908] is applied.
End of informative text.
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