This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the corresponding
Linux manual page for details of Linux behavior), or the interface may not
be implemented on Linux.
stty — set the options for a terminal
stty [-a|-g]
stty operand...
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 the Base Definitions volume of
POSIX.1‐2017, Chapter 11, 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.
The stty utility shall conform to the Base Definitions
volume of POSIX.1‐2017, Section 12.2, 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
Section 2.6, Word Expansions.
The following operands shall be supported to set the terminal
characteristics.
- 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 the Base Definitions volume of
POSIX.1‐2017, Chapter 11, 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
the Base Definitions volume of POSIX.1‐2017, Chapter 11,
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 the Base Definitions volume of POSIX.1‐2017,
Chapter 11, 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 the Base Definitions volume of
POSIX.1‐2017, Chapter 11, 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 the Base
Definitions volume of POSIX.1‐2017, Chapter 11, 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 the Base Definitions volume
of POSIX.1‐2017, Chapter 11, 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 the Base
Definitions volume of POSIX.1‐2017, Chapter 11, 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 the Base Definitions volume of POSIX.1‐2017,
Chapter 11, 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
the Base Definitions volume of POSIX.1‐2017, Chapter 11,
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 the Base Definitions volume of POSIX.1‐2017,
Chapter 11, General Terminal Interface.
It is unspecified whether stty shall report an error if an
attempt to set a Control Mode fails.
- 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 the Base Definitions volume of POSIX.1‐2017,
Chapter 11, 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 the Base Definitions volume of POSIX.1‐2017,
Chapter 11, 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 the Base Definitions volume of
POSIX.1‐2017, Chapter 11, 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
the Base Definitions volume of POSIX.1‐2017, Chapter 11,
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 the Base Definitions volume of POSIX.1‐2017, Chapter
11, 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 the Base Definitions volume of
POSIX.1‐2017, Chapter 11, 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 the Base Definitions volume of POSIX.1‐2017, Chapter 11,
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 the Base Definitions volume of POSIX.1‐2017, Chapter 11,
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 the Base Definitions volume of POSIX.1‐2017, Chapter 11,
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 the Base Definitions
volume of POSIX.1‐2017, Chapter 11, 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 the Base Definitions volume of POSIX.1‐2017, Chapter
11, 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 the Base Definitions
volume of POSIX.1‐2017, Chapter 11, General Terminal
Interface.
- 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 the Base Definitions
volume of POSIX.1‐2017, Chapter 11, General Terminal
Interface.
- onlcr (-onlcr)
- 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 the Base Definitions volume of POSIX.1‐2017, Chapter
11, General Terminal Interface.
- ocrnl (-ocrnl)
- 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 the Base Definitions volume of POSIX.1‐2017, Chapter 11,
General Terminal Interface.
- onocr (-onocr)
- 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 the Base Definitions volume of POSIX.1‐2017, Chapter
11, General Terminal Interface.
- onlret (-onlret)
- 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 the Base Definitions
volume of POSIX.1‐2017, Chapter 11, General Terminal
Interface.
- ofill (-ofill)
- 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 the Base Definitions volume of POSIX.1‐2017, Chapter
11, General Terminal Interface.
- ofdel (-ofdel)
- Fill characters are DELs (NULs). This shall have the effect of setting
(not setting) OFDEL in the termios c_oflag field, as defined
in the Base Definitions volume of POSIX.1‐2017, Chapter 11,
General Terminal Interface.
- cr0 cr1 cr2 cr3
- 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 the Base Definitions volume of
POSIX.1‐2017, Chapter 11, General Terminal
Interface.
- nl0 nl1
- 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 the Base Definitions volume of POSIX.1‐2017,
Chapter 11, General Terminal Interface.
- tab0 tab1 tab2 tab3
-
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 the Base Definitions
volume of POSIX.1‐2017, Chapter 11, General Terminal
Interface. Note that TAB3 has the effect of expanding <tab>
characters to <space> characters.
- tabs (-tabs)
- Synonym for tab0 (tab3).
- bs0 bs1
- Select the style of delay for <backspace> characters. This shall
have the effect of setting BSDLY to BS0 or BS1, respectively, in the
termios c_oflag field, as defined in the Base Definitions
volume of POSIX.1‐2017, Chapter 11, General Terminal
Interface.
- ff0 ff1
- Select the style of delay for <form-feed> characters. This shall
have the effect of setting FFDLY to FF0 or FF1, respectively, in the
termios c_oflag field, as defined in the Base Definitions
volume of POSIX.1‐2017, Chapter 11, General Terminal
Interface.
- vt0 vt1
- Select the style of delay for <vertical-tab> characters. This shall
have the effect of setting VTDLY to VT0 or VT1, respectively, in the
termios c_oflag field, as defined in the Base Definitions
volume of POSIX.1‐2017, Chapter 11, General Terminal
Interface.
- 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 the Base Definitions volume of POSIX.1‐2017, Chapter 11,
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 the Base Definitions volume of
POSIX.1‐2017, Chapter 11, 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 the Base
Definitions volume of POSIX.1‐2017, Chapter 11, 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 the Base Definitions volume of POSIX.1‐2017,
Chapter 11, 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 the Base Definitions volume of POSIX.1‐2017,
Chapter 11, 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 the Base Definitions volume of POSIX.1‐2017, Chapter
11, 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 the Base Definitions volume of
POSIX.1‐2017, Chapter 11, 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 the Base Definitions volume of POSIX.1‐2017,
Chapter 11, 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 the Base Definitions volume of POSIX.1‐2017, Chapter
11, General Terminal Interface.
- <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
the Base Definitions volume of POSIX.1‐2017, Chapter 11,
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 the Base Definitions
volume of POSIX.1‐2017, Chapter 13, Headers,
<termios.h>).
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 <circumflex> ('^'), 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 |
<SOH> |
l, L |
<FF> |
w, W |
<ETB> |
| b, B |
<STX> |
m, M |
<CR> |
x, X |
<CAN> |
| c, C |
<ETX> |
n, N |
<SO> |
y, Y |
<EM> |
| d, D |
<EOT> |
o, O |
<SI> |
z, Z |
<SUB> |
| e, E |
<ENQ> |
p, P |
<DLE> |
[ |
<ESC> |
| f, F |
<ACK> |
q, Q |
<DC1> |
\ |
<FS> |
| g, G |
<BEL> |
r, R |
<DC2> |
] |
<GS> |
| h, H |
<BS> |
s, S |
<DC3> |
^ |
<RS> |
| i, I |
<HT> |
t, T |
<DC4> |
_ |
<US> |
| j, J |
<LF> |
u, U |
<NAK> |
? |
<DEL> |
| k, K |
<VT> |
v, V |
<SYN> |
- 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).
- 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)
-
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.
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.
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 the Base Definitions volume of POSIX.1‐2017,
Section 8.2, 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
print.
- LC_MESSAGES
-
Determine the locale that should be used to affect the format and contents
of diagnostic messages written to standard error.
- NLSPATH
- Determine the location of message catalogs for the processing of
LC_MESSAGES.
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
<space>-separated tokens in an unspecified format, 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.
The standard error shall be used only for diagnostic messages.
The following exit values shall be returned:
- 0
- The terminal options were read or set successfully.
- >0
- An error occurred.
Default.
The following sections are informative.
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.
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 the Base
Definitions volume of POSIX.1‐2017, Chapter 3,
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.
Chapter 2, Shell Command Language
The Base Definitions volume of POSIX.1‐2017, Chapter
8, Environment Variables, Chapter 11, General Terminal
Interface, Section 12.2, Utility Syntax Guidelines,
<termios.h>
Portions of this text are reprinted and reproduced in electronic
form from IEEE Std 1003.1-2017, Standard for Information Technology --
Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the event
of any discrepancy between this version and the original IEEE and The Open
Group Standard, the original IEEE and The Open Group Standard is the referee
document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .
Any typographical or formatting errors that appear in this page
are most likely to have been introduced during the conversion of the source
files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .