Section 3.35. Changing a Terminal s Characteristics: stty

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3.35. Changing a Terminal's Characteristics: stty

All terminals have the ability to process certain characters in a special manner; these characters are called metacharacters. Examples of metacharacters include the backspace character and the Control-C sequence, which is used to terminate programs. The default metacharacter settings may be overridden using the stty utility, described in Figure 3-46.

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Utility: stty -a { option }* { metacharacterString <value>} *

The stty utility allows you to examine and set a terminal's characteristics. stty supports the modification of over one hundred different settings, so I've only listed the most common ones here. Consult man for more details. To list a terminal's current settings, use the -a option. To alter a particular setting, supply one or more of the following options:

OPTION	MEANING
-echo	Don't echo typed characters.
echo	Echo typed characters.
-raw	Enable the special meaning of metacharacters.
raw	Disable the special meaning of metacharacters.
-tostop	Allow background jobs to send output to the terminal.
tostop	Stop background jobs that try to send output to the terminal.
sane	Set the terminal characteristics to sensible default values.

You may also set the mappings of metacharacters by following the name of its corresponding string with its new value. A control character may be indicated by preceding the character with a ^ or by typing a \ followed by the actual control character itself. Here are the common metacharacter strings together with their meanings:

OPTION	MEANING
erase	Backspace one character.
kill	Erase all of the current line.
lnext	Don't treat the next character specially.
susp	Suspend the process for a future awakening.
intr	Terminate (interrupt) the foreground job with no core dump.
quit	Terminate the foreground job with a core dump.
stop	Stop/restart terminal output.
eof	End-of-input.

Here's an example of stty in action:

$ stty -a     ...display current terminal settings. speed 38400 baud; rows 35; columns 80; line = 233; intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = <undef>; eol2 = <undef>; start = ^Q; stop = ^S; susp = ^Z; rprnt = ^R; werase = ^W; lnext = ^V; flush = ^O; min = 1; time = 0; 
[Page 82]-parenb -parodd cs8 -hupcl -cstopb cread -clocal -crtscts -ignbrk brkint ignpar -parmrk -inpck -istrip -inlcr -igncr icrnl ixon -ixoff -iuclc -ixany imaxbel opost -olcuc -ocrnl onlcr -onocr -onlret -ofill -ofdel nl0 cr0 tab0 bs0 vt0 ff0 isig icanon iexten echo echoe echok -echonl -noflsh -xcase -tostop -echoprt echoctl echoke $ stty erase ^b     ...set erase key to Control-B. $ stty erase ^h     ...set erase key to Control-H $ _ 

Invoke stty from your shell's startup file if your favorite metacharacter mappings differ from the norm. stty is useful when building shells that need to turn keyboard echoing on and off; an example of such a script is included in Chapter 8, "The C Shell." Here's an example that uses stty to turn off keyboard echoing:

$ stty -echo     ...turn echoing off. $ stty echo      ...turn echoing back on again. $ _ 

Note that the last line of input (stty echo) would not ordinarily be seen due to the inhibition of echoing caused by the preceding line!

Now that you've seen how to set your terminal type and alter its settings, you can use full-screen editors like vim and emacs.