Linux creating an alias

Using alias Command in Linux to Improve Your Efficiency

Alias command in Linux saves a lot of your time and improves your efficiency. Learn how to use this command properly and see some of the common aliases I use.

As it is known, Linux and Unix were created as command line based systems, which means having control of the commands typed is basically the most important thing to be a *nix SysOp.

This is where ‘alias’ command comes to the show and can be extremely useful, especially for security purposes and to simplify work for a system administrator.

Linux alias command

The shell alias is simply a way to reference another command. It can be used to avoid repetitive long typing of commands and shell lines and simplify work or to even make things safer or dumb-proof.

Take a simple example where you have to use ls command to show everything in reverse chronological order. You can type ls -lrta all the time or you create an alias (say) ‘ll’ that will be equivalent to ls -lrta. It will save you a few keystrokes.

In a similar fashion, you can substitute long and complicated commands with small and simple commands by using alias in Linux.

Let’s see how to make alias in Linux.

How to create alias in Linux

I’ll continue with the same example I used above.

You must note a few things:

• The substituted command is always used under the inverted commas (‘).
• There must be no spaces before or after the equals sign in the alias command. If you mistakenly put a space, you’ll see an error like alias not found.
• Be careful in choosing the name of the alias. There are no reserved keywords so you may replace an existing command with a totally irrelevant command.

You can check if a certain command is actually an alias with the type command. For example, in Ubuntu, ls is actually an alias to show you colorful output.

type ls ls is aliased to `ls --color=auto'

If you want to use the original command, without its aliased version, use single quotes around it.

Now, the alias you just is temporary. If you exit the shell, you’ll lose the alias. You need to make the alias permanent.

Make alias permanent

In order to add aliases that can work in a system all the time, you need to simply edit your user’s (or any other user’s) .bashrc file. Some distributions might suggest using a dedicated .bash_aliases file for storing aliases.

This file is located in your /home// folder. You can use vim command to edit the file in terminal.

This will immediately open your .bashrc file and you must start adding aliases by the end of the file, just after the last written line of it. You should then source the bashrc file.

I suggest creating either blocks or at least adding commentaries in the file for each of the aliases created so it’s easier in the future to know what is each thing for maintenance purposes.

Creating global aliases for all users

If you want the aliases to be available for all users on your Linux system, you should add the aliases in /etc/bash.bashrc file.

If you don’t have this file, create it.

How to see all the alias set on your Linux system for you

If you want to see all the alias set on the system for you, you can check the configuration file of your shell like ~/.bashrc, ~/.zshrc etc.

However, a much easier way to see all the alias would be to simply run the alias command without any arguments.

A typically Ubuntu system has the following alias set by default.

alias alias alert='notify-send --urgency=low -i "$([ $? = 0 ] && echo terminal || echo error)" "$(history|tail -n1|sed -e '''s/^s5+s//;s/[;&|]s*alert$//''')"' alias egrep='egrep --color=auto' alias fgrep='fgrep --color=auto' alias grep='grep --color=auto' alias l='ls -CF' alias la='ls -A' alias ll='ls -lrt' alias ls='ls --color=auto'

How to remove alias

If you want to remove an alias, you can use the unalias command in this manner:

You can remove all alias at once using the -a option:

As with the alias command, changes by unalias command are also temporary. If you wan to remove an alias permanently, you should delete it from the bashrc file.

My favorite alias in Linux I cannot live without

Let me share some aliases that I always use to work more effectively in Linux.

1. Making ‘rm’ safer

As it is well known, rm command is very commonly used day by day and can be also very destructive and disruptive of a system if not properly used.

This is why, I use the following alias:

#make rm command safer alias rm="rm -i" 

This makes ‘rm’ command safer as whenever you use it, it will always ask if you are sure you want to perform the infamous removal operation before proceeding, giving you a second and last chance to not break things unintentionally.

2. Making ssh to other systems easier and faster

Sometimes, especially if you use private keys instead of credentials to log in to other Linux systems, it can be easier to set up aliases for each of them with mnemonic names.

As a SysOp, I use SSH for logging in to different Linux servers and I have several private keys, depending on my clients, therefore it helps me to have aliases such as:

#alias for servers SSH alias sshserver1='ssh -i ~/Documents/IT/SSH-keys/server1.pem [email protected]' alias sshserver2='ssh -i ~/Documents/SSH-keys/server2.pem [email protected]' alias sshplexserverhome='ssh [email protected]' alias sshclientserver='ssh -i ~/Documents/IT/SSH-keys/client.pem [email protected]'

As you can see, I have all my private keys in a folder named “SSH-keys” inside my own user’s folder and then I simply create aliases to connect each of them, following a standard of “ssh”+”name of the server”.

This way I only have to remember the name of the server I want to connect and not where the key is located, the name of each key (if they are different) or even the username that needs to be used for each server to connect.

3. Show time or date for day to day things

Some people either because they script things that use specific times or need to consult time and/or date and want to have in specific formats, can get some benefit of aliases by doing:

alias nowtime='date +"%T"' #this will show the current time in 24hrs format as HH:MM:SS alias nowdate='date +"%d-%m-%Y"' #this will show the current date in format dd-MM-YY

4. Easily manage your iptables information

Let’s face it: iptables or nftables are not the easiest nor friendly thing in the world and even though it’s not hard, the first time you deal with it is not that easy. This is why using aliases such these ones can make things a lot easier:

#Displaying iptables information the easy way :) alias iptlist='sudo /sbin/iptables -L -n -v --line-numbers' #this will display all lines of your current iptables alias iptlistin='sudo /sbin/iptables -L INPUT -n -v --line-numbers' #this will display all your INCOMING rules in iptables alias iptlistout='sudo /sbin/iptables -L OUTPUT -n -v --line-numbers' #this will display all your OUTGOING rules in iptables

5. Update Debian based servers in one single command

I use Ubuntu myself, but you can adapt this for any Red Hat, CentOS servers and ‘yum’ command. Updating a Debian server in a single command could be done through an alias such as this one:

# update on one command alias update='sudo apt-get update && sudo apt-get upgrade'

6. Add an alias to run alias with sudo

You cannot run an alias with sudo by default. If you want to run an aliased command with root access, you’ll have to create an alias with sudo like this:

As you can see, it all depends on what you do and your creativity, but you can basically take the time to create as many aliases as you need for your day to day tasks and make them easier by using this useful ‘alias’ command in Linux.

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Linux alias command: How to create and use Linux aliases

Unix/Linux aliases FAQ: Can you share some examples of the Linux alias command?

Using Linux aliases

Aliases in Unix and Linux operating systems are cool. They let you define your own commands, or command shortcuts, so you can customize the command line, and make it work the way you want it to work. In this tutorial I’ll share several Linux aliases that I use on a daily basis.

Alias examples

I’ve found it very helpful to create aliases to make my command line life easier. For instance, a lot of people don’t like the name of the grep command, and wish they could change it to search . With the alias command you can do exactly that:

Now you can just type search instead of grep at your Linux command line:

search 'Flinstone' StoryOfBedrock.txt

In another simple alias example, instead of always typing this ls command to get a directory listing:

I’ve created an alias so I only have to type the lowercase letter «L» like this:

Whenever I use this alias, it’s exactly the same as if I had typed out the longer ls -al Linux command.

Using aliases like this you can create anything from simple shortcuts like this to powerful custom commands.

How to define a Linux alias

Creating a Linux alias is very easy. You can either enter them at the command line as you’re working, or more likely, you’ll put them in one of your startup files, like your .bash_profile or .bashrc files, so they will be available every time you log in.

I created the l alias above by entering the following command into my .bash_profile file:

As you can see, the Linux alias syntax is very easy:

1. Start with the alias command
2. Then type the name of the alias you want to create
3. Then an = sign, with no spaces on either side of the =
4. Then type the command (or commands) you want your alias to execute when it is run. This can be a simple command, or can be a powerful combination of commands.

Unix/Linux alias examples and syntax

To get you going, here is a list of sample Linux aliases I use all the time. I’ve pretty much just copied them here from my .bashrc file:

alias dirs="ls -al | grep '^d'" alias l="ls -al" alias lf="ls -aFG" alias lm="ls -al|more" alias h="history" alias html="cd /web/apache/htdocs/devdaily/html" alias logs="cd /web/apache/htdocs/devdaily/logs" alias qp="ps auxwww|more" alias nu="who|wc -l" # GIT alias gpom="git push origin master" alias gs="git status" alias gb="git branch" alias gco="git checkout"

As you can see, you can get as creative as you want, and pipe commands together to do just about anything. In the last alias shown I’ve actually combined three Linux commands in a row into one alias to get the output I want.

Because the Unix shell is very programmable and because the output of commands is very consistent and reliable, you can create your own aliases (or macros if you prefer) to do just about anything.

Have a favorite Linux alias?

If you have a favorite Linux alias command/example you’d like to share, feel free to leave it in the comments section below.

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