STTY(1P) POSIX Programmer's Manual STTY(1P)
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NAME
stty - set the options for a terminal
SYNOPSIS
stty [ -a| -g]
stty operands
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. Other-
wise, it shall modify the terminal state according to the specified op-
erands. Detailed information about the modes listed in the first five
groups below are described in the Base Definitions volume of
IEEE Std 1003.1-2001, 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 Inter-
faces volume of IEEE Std 1003.1-2001. 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 the Base Definitions volume of
IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines.
The following options shall be supported:
-a Write to standard output all the current settings for the termi-
nal.
-g Write to standard output all the current settings in an unspeci-
fied 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 Word Expansions .
OPERANDS
The following operands shall be supported to set the terminal charac-
teristics.
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 the Base Definitions volume of
IEEE Std 1003.1-2001, 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 IEEE Std 1003.1-2001, 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
IEEE Std 1003.1-2001, 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 IEEE Std 1003.1-2001, 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 IEEE Std 1003.1-2001,
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 set-
ting the output termios baud rate values as defined in the Base
Definitions volume of IEEE Std 1003.1-2001, 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 set-
ting (not setting) HUPCL in the termios c_cflag field, as
defined in the Base Definitions volume of IEEE Std 1003.1-2001,
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
IEEE Std 1003.1-2001, 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 IEEE Std 1003.1-2001,
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
IEEE Std 1003.1-2001, Chapter 11, 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 the Base Definitions volume of
IEEE Std 1003.1-2001, 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 IEEE Std 1003.1-2001,
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
IEEE Std 1003.1-2001, 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 IEEE Std 1003.1-2001,
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
IEEE Std 1003.1-2001, 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
IEEE Std 1003.1-2001, 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 IEEE Std 1003.1-2001,
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 IEEE Std 1003.1-2001,
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 IEEE Std 1003.1-2001,
Chapter 11, General Terminal Interface.
ixon (-ixon)
Enable (disable) START/STOP output control. Output from the sys-
tem 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 IEEE Std 1003.1-2001, 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
IEEE Std 1003.1-2001, 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 set-
ting) IXOFF in the termios c_iflag field, as defined in the Base
Definitions volume of IEEE Std 1003.1-2001, Chapter 11, 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 the
Base Definitions volume of IEEE Std 1003.1-2001, 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 IEEE Std 1003.1-2001,
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 IEEE Std 1003.1-2001,
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 Def-
initions volume of IEEE Std 1003.1-2001, 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
IEEE Std 1003.1-2001, 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 IEEE Std 1003.1-2001,
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 IEEE Std 1003.1-2001, 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
IEEE Std 1003.1-2001, 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 IEEE Std 1003.1-2001, Chapter 11,
General Terminal Interface. Note that TAB3 has the effect of
expanding <tab>s to <space>s.
tabs (-tabs)
Synonym for tab0 ( tab3).
bs0 bs1
Select the style of delay for backspaces. 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 IEEE Std 1003.1-2001, Chapter 11, General Terminal Interface.
ff0 ff1
Select the style of delay for form-feeds. 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 IEEE Std 1003.1-2001, Chapter 11, General Terminal Interface.
vt0 vt1
Select the style of delay for vertical-tabs. 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 IEEE Std 1003.1-2001, Chapter 11, 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 the Base Definitions volume of
IEEE Std 1003.1-2001, 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 IEEE Std 1003.1-2001, 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) IEX-
TEN in the termios c_lflag field, as defined in the Base Defini-
tions volume of IEEE Std 1003.1-2001, Chapter 11, General Termi-
nal 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
IEEE Std 1003.1-2001, 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 IEEE Std 1003.1-2001, 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
IEEE Std 1003.1-2001, 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
IEEE Std 1003.1-2001, 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
IEEE Std 1003.1-2001, 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 IEEE Std 1003.1-2001,
Chapter 11, 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 Base Definitions volume of
IEEE Std 1003.1-2001, 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
IEEE Std 1003.1-2001, 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 corre-
sponding 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).
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)
Enable (disable) raw input and output. Raw mode shall be equiva-
lent 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 the Base Definitions volume of
IEEE Std 1003.1-2001, Section 8.2, Internationalization Vari-
ables 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, sin-
gle-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 .
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 other-
wise specified, this information shall be written as <space>-separated
tokens in an unspecified format, on one or more lines, with an unspeci-
fied 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 char-
acter 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:
0 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 ter-
minal 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 imple-
mentations 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 charac-
ters 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
IEEE Std 1003.1-2001. 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 charac-
ters because the control characters were not specified in the POSIX
locale character set description file requirements. The control char-
acter set is now specified in the Base Definitions volume of
IEEE Std 1003.1-2001, 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 encod-
ings.
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 ter-
minal 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 out-
put to be redirected for later use. Therefore, usage of standard input
is required by this volume of IEEE Std 1003.1-2001.
FUTURE DIRECTIONS
None.
SEE ALSO
Shell Command Language, the Base Definitions volume of
IEEE Std 1003.1-2001, Chapter 11, General Terminal Interface,
<termios.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 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 .
IEEE/The Open Group 2003 STTY(1P)
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