Viewing & editing files

This page concentrates on doing things on the command line. That knowledge makes you more flexible and able to work when no desktop environment is available, such as when logging into a Linux machine remotely with PuTTY.

The basic command to show the contents of a file is cat, e.g.:

cat readme.txt

If the file is long, cat won't be convenient, because it means you need to scroll back to see the start. Viewing a long text file conveniently can be done with less, e.g.:

less readme.txt

It can also be used to scroll through the text output of a previous command by piping it through, e.g.:

ls -lR | less

The basic usage of less is intuitive: the arrows keys and page up/down work to scroll through the text. You only need to learn that the q key is for quitting. It has more tricks up its sleeve though:

For historical reasons different computer systems represent a line break in text with different characters. It is good to be aware of this as it can cause some incompatibilities to this day. All systems use either the Carriage Return (CR) and/or Line Feed (LF).

These different methods exist:

Nano is a nice and simple text editor that even has syntax highlighting. A text file can be opened with:

nano readme.txt

The keys for Nano are shown at the bottom the screen (such as Ctrl+X for exit):

Vim (VIsual editor iMproved) is what the name suggests: an improved version of the older Vi editor. It takes a bit longer to learn this editor, but it has loads of features that can make you really productive. It is my editor of choice. A text file can be opened with:

vim readme.txt

Vim has two modes: the command mode and insert mode. By default it is in command mode and most keys on the keyboards make the editor do something. The x key means delete for example. To enter so-called Ex commands you need to first type : and then the command. Opening a file and quitting are done with Ex commands. You need to use the i key to switch to insert mode. Then you can add/remove/change text as usual. Returning back to command mode is done with the Esc key or Ctrl+[.

The basic keys in command mode are:

You can put settings for Vim in ~/.vimrc. I advice the following:

syntax on           " Enable syntax highlighting
set background=dark " Assume dark background for syntax highlighting
set nowrap          " Don't wrap long lines
set ic              " Ignore case when searching

A screenshot of Vim with syntax highlighting enabled:

Emacs is the other famous advanced editor. A text file can be opened with:

emacs readme.txt

It doesn't have two modes like Vim. You can directly edit text when opened. Commands are given with the Ctrl key. Basic keys are:

Like Vim the colors won't be right be default in case you have a dark background. To fix that put this in ~/.emacs:

;; dark mode
(when (display-graphic-p)
  (invert-face 'default)
)

Screenshot of Emacs:

This is not essential, but a few programs (such as less) make use of either environment variable VISUAL or EDITOR to determine which editor to open. You can customize this to your preferred editor by including this in ~/.bashrc:

export VISUAL=nano
export EDITOR=nano