bash Cookbook

Doing More with less

"less is more!”

Problem

You’d like to take better advantage of the features of the less pager.

Solution

Read the less manpage and use the $LESS variable with ~/.lessfilter and ~/.lesspipe files.

less takes options from the $LESS variable, so rather than creating an alias with your favorite options, put them in that variable. It takes both long and short options, and any command-line options will override the variable. We recommend using the long options in the $LESS variable since they are easy to read. For example:

export LESS="--LONG-PROMPT --LINE-NUMBERS --ignore-case --QUIET"

But that is just the beginning. less is expandable via input preprocessors, which are simply programs or scripts that pre-process the file that less is about to display. This is handled by setting the $LESSOPEN and $LESSCLOSE environment variables appropriately.

You could build your own, but save yourself some time and look into Wolfgang Friebel’s lesspipe.sh available at http://www-zeuthen.desy.de/~friebel/unix/lesspipe.html (but see the discussion below first). The script works by setting and exporting the $LESSOPEN environment variable when run by itself:

$ ./lesspipe.sh
LESSOPEN="|./lesspipe.sh %s"
export LESSOPEN

So you simply run it in an eval statement, like eval $(/path/to/lessfilter.sh) or eval`/path/to/lessfilter.sh`, and then use less as usual. The list of supported formats for version 1.53 is:

gzip, compress, bzip2, zip, rar, tar, nroff, ar archive, pdf, ps, dvi, shared library, executable, ...