Less Tricks For The Command Line

Less tricks for more productivity on the command line. Pun intended.

Introduction

less is a command line program that lets you display the contents of files in the Linux terminal.

I have been a user of cat and grep combination (cat file.txt | grep foo) for a long time, but we can do better.

less doesn’t have to load the whole file in memory and can search and do other small things that might help you.

less is also used when you read man pages, i.e.: man less will open a less process :-).

What follows are just basic features of less that I use on a daily basis, for more advanced usage see its man page.

Searching

After having opened a file in less less file.txt you can start searching for keywords by pressing / and typing the search term. Like so: /foobar

There can be no results or several, to navigate backwards and forwards press N (Shift + n) and n.

Filtering

Apart from searching we can also only display data that we’re interested in or we can hide data that we’re not interested in.

This is done similarly to searching:

&foobar

This will only display lines from your file that contain the term, all other will be hidden.

In order to exclude lines containing a term, just negate it using !, like this:

&!foobar

Will hide all lines that do contain the “foobar” term.

Note: Both the filtering and the searching features have a history of terms, after typing either / or & use the up arrow to see term previously used.

Line numbers

You can also display line numbers and they will also be filtered in/out so you can see which lines match your criteria.

For this you’ll have to type -N and press Enter.

In order to turn off the line numbers, repeat the sequence.

Follow

If you ever used tail -f file.txt to see the contents of a log file while they are changing, well… less provides a similar functionality, you either have to start it with the -F flag:

less +F file.txt

Or you can use this functionality by pressing F (Shift + f) in order to make it watch for content changes.

In order to stop watching for changes, press Ctrl + c.

Very handy feature when you want to follow a log file.

Colored output

If you have colordiff installed, a little thing I like to do and use almost daily is:

svn diff | colordiff | less -R

This will simulate for SVN what git diff does out of the box.

This demonstrates that less can output colors as well and the pagination comes in handy so your terminal stays clean after viewing the diff.

Thumbnail image from https://pixabay.com/