Exit from less by pressing ESC key

Question

Can I setup less program to exit from it by pressing ESC key?

Answer 1

To bind Esc+Esc to quit with lesskey, do the following:

1. Create a ~/.lesskey file with the line:

\e\e quit

2. Run lesskey. This will create a binary ~/.less file used by less.

3. Use less as usual. Esc+Esc will do a quit.

If you no longer want your bindings, you can remove the ~/.less file.

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For more details, see man lesskey or lesskey.nro in the less package source.
Debian -- Details of source package less in wheezy

SYNOPSIS
       lesskey [-o output] [--] [input]

The input file is a text file which describes the key bindings.
If the input file is "-", standard input is read.
If no input file is specified, a standard filename is used
as the name of the input file, which depends on the system being used:
On Unix systems, $HOME/.lesskey is used;
on MS-DOS systems, $HOME/_lesskey is used;
and on OS/2 systems $HOME/lesskey.ini is used,
or $INIT/lesskey.ini if $HOME is undefined.

Answer 2

Not really.

less has many functions bound to ESC + something else. See the manpage: ESCv, ESCn, ESCF, many others. You wouldn't be able to type any of those is less exited upon receiving just ESC.

Concievably, you could rebind all those functions to other keystrokes or live with being unable to type them, and rebind ESC to quitting, but it still wouldn't be a good idea.

It's not a good choice of key to use. In VT100 (the terminal emulation used basically everywhere these days) all terminal control sequences begin with the ASCII ESC character. This means that every time you press something like an arrow key, your terminal sends ESC followed by other stuff. When you press the ESC key, your terminal also sends ESC, but it's not followed by anything. How can software tell the difference after having received an ASCII ESC character? It is forced to wait a some time to see if anything follows the ESC. So things bound to ESC alone always incur a delay, a time lag before the software can respond.