STTY(1)

NAME
stty - set the options for a terminal device interface

SYNOPSIS
stty [-a | -e | -g] [-f file] [arguments]

DESCRIPTION
The stty utility sets or reports on terminal characteristics for the device that is its standard input. If no options or arguments 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 following options are available:

-a  Display all the current settings for the terminal to standard output as per p1003.2.

-e  Display all the current settings for the terminal to standard output in the traditional BSD ``all'' and ``everything'' formats.

-f  Open and use the terminal named by file rather than using standard input. The file is opened using the O_NONBLOCK flag of open(), 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 as per p1003.2.

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.

rtsdtr (-rtsdtr)
    Enable (disable) asserting RTS/DTR on open.

  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) characters with parity errors.

parmrk (-parmrk)
    Mark (do not mark) characters with 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.

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.

iutf8 (-iutf8)
    Assume that input characters are UTF-8 encoded. Setting this flag causes backspace to properly delete multibyte characters in canonical mode.

  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)
    Map (do not map) CR to NL on output.

tab0 tab3
    Select tab expansion policy. tab0 disables tab expansion, while tab3 enables it.

onocr (-onocr)
    Do not (do) output CRs at column zero.

onlret (-onlret)
    On the terminal NL performs (does not perform) the CR function.

  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.

  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- | |
    character | Subscript | Description
    _________ | _________ | _______________
    eof | VEOF | EOF character
    eol | VEOL | EOL character
    eol2 | VEOL2 | EOL2 character
    erase | VERASE | ERASE character
    erase2 | VERASE2 | ERASE2 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, ERASE2, 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.

    If the sysctl(8) variable kern.tty_info_kstacks is set to a non-zero value, the status message also includes the kernel program stack of the foreground thread.

columns number
    The terminal size is recorded as having number columns.

cols number
    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.

litout (-litout)
    The converse of opost.

oxtabs (-oxtabs)
    Expand (do not expand) tabs to spaces on output.

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.

INTERACTION WITH JOB CONTROL
Modifications to the terminal settings are treated by job control (see termios(4)) same as writes. When the stty utility is executing in a background process group, such attempts result in the kernel sending the SIGTTOU signal and stopping the process until its group is returned to foreground. The non-blocking open of the terminal device with the -f option to stty does not affect the behavior. If it is desirable to modify the settings from the background, sh(1) users might utilize the following idiom:

    (trap '' TTOU; stty -f /dev/tty sane)

Note that changing terminal settings for a running foreground job that is not prepared for it might cause inconsistencies.

EXIT STATUS

SEE ALSO
resizewin(1), termios(4), pstat(8)

STANDARDS
The stty utility is expected to be p1003.2 compatible. The flags -e and -f are extensions to the standard.

HISTORY
A stty command appeared in AT&T UNIX.