stty command

Purpose

Sets, resets, and reports workstation operating parameters.

Syntax

stty [ -a ] [ -g ] [ Options ]

Description

The stty command sets certain I/O options for the device that is the current standard input. This command writes output to the device that is the current standard output.

This version of the operating system uses the standard interface to control the terminals, maintaining a compatibility with POSIX and BSD interfaces. The stty command supports both POSIX and BSD compliant options, but the usage of POSIX options is strongly recommended. A list of obsolete BSD options, with the corresponding POSIX options, is also provided.

When you redirect standard input from a tty device by typing:

 stty -a </dev/ttyx

the stty command (POSIX) will hang while waiting for the open() of that tty until the RS-232 carrier detect signal has been asserted. Exceptions to this rule occur if the clocal or forcedcd (128-port only) option is set.

Flags

-a	Writes the current state of all option settings to standard output.
-g	Writes option settings to standard output in a form usable by another stty command.

Options

The stty command supports following categories of options:

Control modes
Input modes
Output modes
Local modes
Hardware flow control modes
Control assignments
Combination modes
Window size
Obsolete options

Control modes

Control mode	Description
clocal	Assumes a line without modem control.
-clocal	Assumes a line with modem control.
cread	Enables the receiver.
-cread	Disables the receiver.
cstopb	Selects 2 stop bits per character.
-cstopb	Selects 1 stop bit per character.
cs5, cs6, cs7, cs8	Selects character size.
hup, hupcl	Hangs up dial-up connection on the last close.
-hup, -hupcl	Does not hang up dial-up connection on the last close.
parenb	Enables parity generation and detection.
-parenb	Disables parity generation and detection.
parodd	Selects odd parity.
-parodd	Selects even parity.
0	Hangs up phone line immediately.
speed	Sets the workstation input and output speeds to the specified speed number of bits per second. All speeds are not supported by all hardware interfaces. Possible values for speed are: 50, 75, 110, 134, 200, 300, 600, 1200, 1800, 2400, 4800, 9600, 19200, 19.2, 38400, 38.4, exta, and extb. Note: exta, 19200, and 19.2 are synonyms; extb, 38400, and 38.4 are synonyms.
ispeed speed	Sets the workstation input speed to the specified speed number of bits per second. All speeds are not supported by all hardware interfaces, and all hardware interfaces do not support this option. Possible values for speed are the same as for the speed option.
ospeed speed	Sets the workstation output speed to the specified speed number of bits per second. All speeds are not supported by all hardware interfaces, and all hardware interfaces do not support this option. Possible values for speed are the same as for the speed option.

Input modes

Input mode	Description
brkint	Signals INTR on break.
-brkint	Does not signal INTR on break.
icrnl	Maps CR to NL on input.
-icrnl	Does not map CR to NL on input.
ignbrk	Ignores BREAK on input.
-ignbrk	Does not ignore BREAK on input.
igncr	Ignores CR on input.
-igncr	Does not ignore CR on input.
ignpar	Ignores parity errors.
-ignpar	Does not ignore parity errors.
inlcr	Maps NL to CR on input.
-inlcr	Does not map NL to CR on input.
inpck	Enables parity checking.
-inpck	Disables parity checking.
istrip	Strips input characters to 7 bits.
-istrip	Does not strip input characters to 7 bits.
iuclc	Maps uppercase alphabetic characters to lowercase.
-iuclc	Does not map uppercase alphabetic characters to lowercase.
ixany	Allows any character to restart output.
-ixany	Allows only the START (the Ctrl-Q key sequence) to restart output.
ixoff	Sends START/STOP characters when the input queue is nearly empty/full.
-ixoff	Does not send START/STOP characters.
ixon	Enables START/STOP output control. Once START/STOP output control has been enabled, you can pause output to the workstation by pressing the Ctrl-S key sequence and resume output by pressing the Ctrl-Q key sequence.
-ixon	Disables START/STOP output control.
imaxbel	Echoes the BEL character and discards the last input character if input overflows.
-imaxbel	Discards all input if input overflows.
parmrk	Marks parity errors.
-parmrk	Does not mark parity errors.

Output modes

Output mode	Description
bs0, bs1	Selects style of delay for backspaces (bs0 siginifes no delay).
cr0, cr1, cr2, cr3	Selects style of delay for CR characters (cr0 siginifes no delay).
ff0, ff1	Selects style of delay for form feeds (ff0 siginifes no delay).
nl0, nl1	Selects style of delay for NL characters (nl0 siginifes no delay).
ofill	Uses fill characters for delays.
-ofill	Uses timing for delays.
ocrnl	Maps CR characters to NL characters.
-ocrnl	Does not map CR characters to NL characters.
olcuc	Maps lowercase alphabetic characters to uppercase on output.
-olcuc	Does not map lowercase alphabetic characters to uppercase on output.
onlcr	Maps NL characters to CR-NL characters.
-onlcr	Does not map NL characters to CR-NL characters.
onlret	On the terminal, NL performs the CR function.
-onlret	On the terminal, NL does not perform the CR function.
onocr	Does not output CR characters at column zero.
-onocr	Outputs CR characters at column zero.
opost	Processes output.
-opost	Does not process output; that is, ignores all other output options.
ofdel	Uses DEL characters for fill characters.
-ofdel	Uses NUL characters for fill characters.
tab0, tab1, tab2	Selects style of delay for horizontal tabs (tab0 siginifes no delay).
tab3	Expands tab character to variable number of spaces.
vt0, vt1	Selects style of delay for vertical tabs (vt0 siginifes no delay).

Local modes

Local mode	Description
echo	Echoes every character typed.
-echo	Does not echo characters.
echoctl	Echoes control characters as ^X (Ctrl-X), where X is the character given by adding 100 octal to the code of the control character.
-echoctl	Does not echo control characters as ^X (Ctrl-X).
echoe	Echoes the ERASE character as the "backspace space backspace" string. Note: This mode does not keep track of column position, so you can get unexpected results when erasing such things as tabs and escape sequences.
-echoe	Does not echo the ERASE character, just backspace.
echok	Echoes a NL character after a KILL character.
-echok	Does not echo a NL character after a KILL character.
echoke	Echoes the KILL character by erasing each character on the output line.
-echoke	Just echoes the KILL character.
echonl	Echoes the NL character.
-echonl	Does not echo the NL character.
echoprt	Echoes erased characters backwards with / (slash) and \ (backslash).
-echoprt	Does not echo erased characters backwards with / (slash) and \ (backslash).
icanon	Enables canonical input (canonical input allows input-line editing with the ERASE and KILL characters).
-icanon	Disables canonical input.
iexten	Specifies that implementation-defined functions shall be recognized from the input data. Recognition of the following control characters requires iexten to be set: eol2, dsusp, reprint, discard, werase, lnext. The functions associated with these modes also require iexten to be set: imaxbel, echoke, echoprt, and echoctl.
-iexten	Specifies that implementation-defined functions shall not be recognized from the input data.
isig	Enables the checking of characters against the special control characters INTR, SUSP and QUIT.
-isig	Disables the checking of characters against the special control characters INTR, SUSP and QUIT.
noflsh	Does not clear buffers after INTR, SUSP, or QUIT control characters.
-noflsh	Clears buffers after INTR, SUSP, or QUIT control characters.
pending	Causes any input that is pending after a switch from raw to canonical mode to be re-input the next time a read operation becomes pending or the next time input arrives. Pending is an internal state bit.
-pending	No text is pending.
tostop	Signals SIGTOU for background output.
-tostop	Does not signal SIGTOU for background output.
xcase	Echoes uppercase characters on input, and displays uppercase characters on output with a preceding \ (backslash).
-xcase	Does not echo uppercase characters on input.

Hardware flow control modes

These options are extensions to the X/Open Portability Guide Issue 4 standard.

Extension	Description
cdxon	Enables CD hardware flow control mode on output.
-cdxon	Disables CD hardware flow control mode on output.
ctsxon	Enables CTS hardware flow control mode on output.
-ctsxon	Disables CTS hardware flow control mode on output.
dtrxoff	Enables DTR hardware flow control mode on input.
-dtrxoff	Disables DTR hardware flow control mode on input.
rtsxoff	Enables RTS hardware flow control mode on input.
-rtsxoff	Disables RTS hardware flow control mode on input.

Control assignments

To assign a control character to a character string, type:

stty Control String

where the Control parameter may be the INTR, QUIT, ERASE, KILL, EOF, EOL, EOL2, START, STOP, SUSP, DSUSP, REPRINT, DISCARD, WERASE, LNEXT, MIN, or TIME character. (Use the MIN and TIME characters with the -icanon option.)

Note: The values for MIN and TIME are interpreted as integer values, not as character values.

The String parameter may be any single character such as c. An example of this control assignment is:

stty STOP c

Another way of assigning control characters is to enter a character sequence composed of a \^ (backslash, caret) followed by a single character. If the single character after the ^ (caret) is one of the characters listed in the ^c (caret c) column of the following table, the corresponding control character value will be set. For example, to assign the DEL control character by using the ? (question mark) character, type the string \^? (backslash, caret, question mark), as in:

stty ERASE \^?

^c	Value
a, A	<SOH>
b, B	<STX>
c, C	<ETX>
d, D	<EOT>
e, E	<ENQ>
f, F	<ACK>
g, G	<BEL>
h, H	<BS>
i, I	<HT>
j, J	<LF>
k, K	<VT>
l, L	<FF>
m, M	<CR>
n, N	<SO>
o, O	<SI>
p, P	<DLE>
q, Q	<DC1>
r, R	<DC2>
s, S	<DC3>
t, T	<DC4>
u, U	<NAK>
v, V	<SYN>
w, W	<ETB>
x, X	<CAN>
y, Y	<EM>
z, Z	<SUB>
[	<ESC>
\	<FS>
]	<GS>
^	<RS>
_	<US>
?	<DEL>
@	<NUL>

Combination modes

Combination mode	Description
cooked	See the -raw option.
ek	Sets ERASE and KILL characters to the Ctrl-H and Ctrl-U key sequences, respectively.
evenp	Enables parenb and cs7.
-evenp	Disables parenb and sets cs8.
lcase, LCASE	Sets xcase, iuclc, and olcuc. Used for workstations with uppercase characters only.
-lcase, -LCASE	Sets -xcase, -iuclc, and -olcuc.
nl	Sets -icrnl and -onlcr.
-nl	Sets icrnl, onlcr, -inlcr, -igncr, -ocrnl, and -onlret.
oddp	Enables parenb, cs7, and parodd.
-oddp	Disables parenb and sets cs8.
parity	See the evenp option.
-parity	See the -evenp option.
sane	Resets parameters to reasonable values.
raw	Allows raw mode input (no input processing, such as erase, kill, or interrupt); parity bit passed back.
-raw	Allows canonical input mode.
tabs	Preserves tabs.
-tabs, tab3	Replaces tabs with spaces when printing.

Window size

Window size	Description
cols n, columns n	The terminal (window) size is recorded as having n columns.
rows n	The terminal (window) size is recorded as having n rows.
size	Prints the terminal (window) sizes to standard output (first rows and then columns).

Obsolete options

The following BSD options are supported by the stty command. For each of them, the recommended POSIX option is given.

Option	Description
all	Use the stty -a command to display all current settings.
crt	Use the sane option to reset parameters to reasonable values.
crtbs	Use the -echoe option.
crterase	Use the echoe option.
-crterase	Use the -echoe option.
crtkill	Use the echoke option.
-crtkill	Use the echok and -echoke options.
ctlecho	Use the echoctl option.
-ctlecho	Use the -echoctl option.
decctlq	Use the -ixany option.
-decctlq	Use the ixany option.
even	Use the evenp option.
-even	Use the -evenp option.
everything	Use the stty -a command to display all current settings.
litout	Use the -opost option.
-litout	Use the opost option.
odd	Use the oddp option.
-odd	Use the -oddp option.
pass8	Use the -istrip option.
-pass8	Use the istrip option.
prterase	Use the echoprt option.
speed	Use the stty command to display current settings.
tandem	Use the ixoff option.
-tandem	Use the -ixoff option.

Examples

To display a short listing of your workstation configuration, type:
```
stty
```
This lists settings that differ from the defaults.
To display a full listing of your workstation configuration, type:
stty -a
To enable a key sequence that stops listings from scrolling off the screen, type:
```
stty ixon ixany
```
This sets ixon mode, which lets you stop runaway listing by pressing the Ctrl-S key sequence. The ixany flag allows you to resume the listing by pressing any key. The normal workstation configuration includes the ixon and ixany flags, which allows you to stop a listing with the Ctrl-S key sequence that only the Ctrl-Q key sequence will restart.
To reset the configuration after it has been messed up, type:
Ctrl-J stty sane Ctrl-J
Press the Ctrl-J key sequence before and after the command instead of the Enter key. The system usually recognizes the Ctrl-J key sequence when the parameters that control Enter key processing are messed up.
Sometimes the information displayed on the screen may look strange, or the system will not respond when you press the Enter key. This can happen when you use the stty command with parameters that are incompatible or that do things you don't understand. It can also happen when a screen-oriented application ends abnormally and does not have a chance to reset the workstation configuration.

Entering the stty sane command sets a reasonable configuration, but it may differ slightly from your normal configuration.
To save and restore the terminal's configuration:
```
OLDCONFIG=`stty -g`          # save configuration
stty -echo                   # do not display password
echo "Enter password: \c"
read PASSWD                  # get the password
stty $OLDCONFIG              # restore configuration
```
This command saves the workstation's configuration, turns off echoing, reads a password, and restores the original configuration.
Entering the stty -echo command turns off echoing, which means that the password does not appear on the screen when you type it at the keyboard. This action has nothing to do with the echo command, which displays a message on the screen.

File

/usr/bin/stty

Contains the stty command.