Boost Your Command Line Skills with These Secret Commands

We use several commands on different unix-like operating systems but there are some lesser known hidden gems that can make their work easier and faster.

This article will introduce you to some hidden gems or useful Linux commands that can help you perform various tasks more efficiently and effectively which scripting or casually administrating a system.

Shell built-ins

A shell built-in (command) is a command that is part of the shell, i.e. bash, zsh, etc., itself, rather than a separate executable file. They are faster as they don’t require creating a new process and loading a binary file.

You can use a shell built-in or type command to check if a command is a built-in or an external one as follows:

$ type cd
cd is a shell builtin
$ type nano
ls is /usr/bin/nano
$ type ls
ls is aliased to `ls --color=auto'

As you can see, cd is a built-in command, while nano is an external one located in /usr/bin/nano.

Useful shell built-in commands

There are many shell built-in commands available in Bash, the most common Linux shell.

You can use the help command to see a list of all of them and their descriptions.

Here are some of the most useful ones that you should know:

1. export

The export command sets or displays environment variables, used to store configuration settings or preferences for programs. Learn more at the export command tutorial.

You can set an environment variable with the syntax export name=value and display all environment variables using export without any arguments.

export LANG=en_US.UTF-8
export

declare -x HOME="/home/user"
declare -x LANG="en_US.UTF-8"
declare -x PATH="/usr/local/bin:/usr/bin:/bin:/home/user/.local/bin"
...

We can see all environment variables set including LANG which we just updated.

2. alias

The alias command creates or displays aliases for commands. Aliases are shortcuts or alternative names for commands that can save you typing time or make commands more memorable.

To create an alias, you need use the syntax alias name='command'.

alias la='ls -al'

Now we can use la instead of typing ls -al. You can display all aliases with 'alias' command.

unalias

The unalias command removes aliases for commands as shown below:

unalias ll

This removes the ll alias that we created earlier.

3. source

The source command executes commands from a file in the current shell. Here is a complete tutorial on the source command.

source ~/.bashrc

This executes the commands in the .bashrc file, which is a common file that stores settings and preferences for the Bash shell.

4. test

The test command evaluates a conditional expression and returns a true or false value. The expression can be a comparison of strings, numbers, or files, or a logical combination of other expressions. Learn more at how to check if file exists tutorial.

The test command is often used in conjunction with if, while, or case statements to control the flow of a script as shown in the code snippet given below:

$ test 1 -eq 1
$ echo $?
0
$ test 1 -eq 2
$ echo $?
1

It returns 0 (means true) if the expression is true, and 1 (means false) if the expression is false.

Useful hidden commands in Linux and Unix

There are many less known or less frequently used commands, but can be very helpful for certain tasks.

Here is a list of such commands along with their descriptions and example usage:

Top 10 Hardware Information Commands

Some of the complex commands to learn happen to be the hardware ones.

Here are most useful hardware related commands to remeber as a system administrator:

We hope you found this article helpful and informative to learn some of the most useful shell built-in commands and how to use them. Thank you for reading!