The 4 commands above apply to terminal sessions only.
The stty command lets us determine the terminal settings currently in use…
root:/tmp> stty -a
speed 38400 baud; rows 62; columns 171; line = 0;
intr = ^C; quit = ^; erase = ^?; kill = ^U; eof = ^D; eol = M-^?; eol2 = M-^?; swtch = M-^?;
start = ^Q; stop = ^S; susp = ^Z; rprnt = ^R; werase = ^W; lnext = ^V;
flush = ^O; min = 1; time = 0;
-parenb -parodd -cmspar cs8 hupcl -cstopb cread -clocal -crtscts
-ignbrk brkint -ignpar -parmrk -inpck -istrip -inlcr -igncr -icrnl ixon -ixoff -iuclc ixany
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
… as well as change whatever needs changing. As we see above, there are many parameters and options we can tweak but we will rarely need to change most of them. Some of the most common parameters that we would need to know about are:
intr SIGINT signal is usually triggered by Control+C
quit SIGQUIT signal is usually triggered by Control+
erase erase action is usually mapped to the Backspace key
kill SIGKILL signal is usually triggered by Control+U
eof endoffeed or endofinput is usually triggered by Control+D
susp SIGSTOP signal is usually triggered by Control+Z
start restarting stopped output is usually achieved with Control+Q
stop stopping output is usually achieved with Control+S
# following settings are disabled with “” prefix
ixon enables/disables start/stop output keys
isign enables/disables intr/quit/susp keys
icanon enables/disables erase/kill/werase/rprnt keys
echo enabled by default as we want to see what we type but might be disabled (password input?)
tostop disabled by default. When enabled stops background processes trying to write to terminal
Let’s set a few common terminal settings to get a grip on this:
root:~> stty erase <Backspace> → resets the mapping of erase to the Backspace key
root:~> stty quit <Control+Q> → SIGQUIT will be triggered by Control+Q
root:~> stty -icanon → disable erase/kill/werase/rprnt keys
If the settings are messed up and we want to reset them all to their default values we can do so with:
root:~> stty sane
For a thorough explanation of all the parameters and options run: “info coreutils ‘stty invocation‘ ” .
The tty command does not have much to talk about, it simply shows us our own terminal device…
… but it can be used from within a script to determine whether or not stdout is a terminal:
root:~> tty -s
root:~> echo $?
Zero means stdout is the terminal and one means it isn’t.
When we have the terminal full of output and we want it totally clean and empty (apart from prompt) we just need to execute clear without any arguments and that will do the trick.
If the terminal is misconfigured or its character set has accidentally changed (cating a binary file sometimes does that…), we can reset all the defaults and get a clean terminal again with the reset command.