Alias commands in linux

Изучаем команды Linux: alias

1. Введение

Команда alias — это очень удобный инструмент для тех, кто часто работает в командной строке. При правильных установках она поможет вам быстрее вводить команды, а также исправлять опечатки. alias — это встроенная команда оболочки, поэтому инсталлировать ее не требуется. В данной статье мы подробно расскажем об использовании команды alias в операционной системе Linux и покажем на примерах.

2. Что представляет собой команда alias в Linux?

alias используется для создания альтернативных версий обычных команд, присваивая им новые названия, а также чтобы избежать необходимости запоминать длинные и сложные команды. Кроме того, вы можете задать опции по умолчанию, которые используются каждый раз при запуске команды alias.

3. Как создавать алиасы в Linux

Сколько раз вам случалось набирать sl вместо ls, получая в результате сообщение об ошибке:

Давайте на базе приведенного выше примера покажем, как создавать алиасы в Linux, чтобы избежать появления этого сообщения об ошибке. Чтобы создать алиас, используется команда alias со следующим синтаксисом:

Мы можем создать новый алиас «sl», который будет являться альтернативной командой для ls.

Из приведенного выше примера вы можете видеть, что мы создали новый алиас «sl», при выполнении которого запускается команда ls. Это простой пример создания алиаса. Вы также можете включать в алиас опции или несколько команд, используя одинарные кавычки. Для примера давайте создадим алиас, который будет показывать наш внешний IP-адрес:

Запустите вышеприведенную команду одной строкой, чтобы создать новый алиас myip, который будет показывать ваш внешний IP:

Необходимо отметить, что с помощью команды alias вы создаете алиас только для текущей сессии командной оболочки. Это значит, что как только вы разлогинитесь, или откроете новый терминал, созданные вами алиасы уже не будут работать. В следующем разделе мы узнаем, как создавать постоянные алиасы.

4. Создание постоянных алиасов

Вы можете сделать все свои алиасы постоянными. Для этого вы можете определить алиасы путем включения их в свой локальный файл

/.bashrc. Здесь мы предполагаем, что в качестве командной оболочки вы используете bash.

Рассмотрим этот пример подробно, строка за строкой.
Мы исполняем команду ls без опции -l показа подробностей. Далее мы вставляем новый алиас ls с опцией -l в файл

/.bashrc (скрытый файл в вашей домашней директории). Вместо команды echo вы можете использовать любой текстовый редактор. Важно отметить, что если вы решите использовать команду echo, как и в приведенном выше примере, убедитесь сначала, что вы сделали резервную копию файла

/.bashrc, и что вы используете оператор >> вместо >.
С помощью оператора «.» мы перегрузили файл

/.bashrc. Это значит, что окружение bash было обновлено с включением в него нашего алиаса. То же самое автоматически происходит при перезагрузке или новой авторизации в оболочке. Теперь наш алиас стал постоянным.
И в последнюю очередь мы выполняем команду ls, которая теперь включает опцию -l.

5. Просмотр списка алиасов

Чтобы просмотреть список всех доступных алиасов, просто выполните команду alias без аргументов (в некоторых системах используется опция -p):

6. Удаление алиасов

Если алиас вам больше не нужен, вы можете удалить его из системы, используя команду unalias. В качестве аргумента вставьте имя алиаса, который вы хотите удалить.

Если вы определили свой алиас в файле

./bashrc, вам также необходимо удалить определение алиаса, иначе он снова будет определен после старта нового сеанса командной оболочки или перезагрузки компьютера.

7. Заключение

Алиасы — удобный инструмент, позволяющий повысить эффективность работы в командной строке Linux. Он прост в настройке и использовании. Большинство систем Linux уже имеют набор предопределенных алиасов. Вы можете проверить их, изменить или добавить нужный вам. Хорошим кандидатом для алиаса будет длинная и скучная команда, которую, тем не менее, вы используете регулярно.

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How to Create and Use Alias Command in Linux

Linux users often need to use one command over and over again. Typing or copying the same command again and again reduces your productivity and distracts you from what you are actually doing.

You can save yourself some time by creating aliases for your most used commands. Aliases are like custom shortcuts used to represent a command (or set of commands) executed with or without custom options. Chances are you are already using aliases on your Linux system.

List Currently Defined Aliases in Linux

You can see a list of defined aliases on your profile by simply executing alias command.

Here you can see the default aliases defined for your user in Ubuntu 18.04.

List Aliases in Linux

As you can see, executing.

Is equivalent to running:

You can create an alias with a single character that will be equivalent to a command of your choice.

How to Create Aliases in Linux

Creating aliases is relatively easy and quick process. You can create two types of aliases – temporary ones and permanent. We will review both types.

Creating Temporary Aliases

What you need to do is type the word alias then use the name you wish to use to execute a command followed by «=» sign and quote the command you wish to alias.

The syntax is as follows:

Here is an actual example:

You can then use «wr» shortcut to go to the webroot directory. The problem with that alias is that it will only be available for your current terminal session.

If you open new terminal session, the alias will no longer be available. If you wish to save your aliases across sessions you will need a permanent alias.

Creating Permanent Aliases

To keep aliases between sessions, you can save them in your user’s shell configuration profile file. This can be:

The syntax you should use is practically the same as creating a temporary alias. The only difference comes from the fact that you will be saving it in a file this time. So for example, in bash, you can open .bashrc file with your favorite editor like this:

Find a place in the file, where you want to keep the aliases. For example, you can add them in the end of the file. For organizations purposes you can leave a comment before your aliases something like this:

Save the file. The file will be automatically loaded in your next session. If you want to use the newly defined alias in the current session, issue the following command:

To remove an alias added via the command line can be unaliased using unalias command.

Conclusion

This was a short example on how to create your own alias and execute frequently used commands without having to type each command again and again. Now you can think about the commands you use the most and create shortcuts for them in your shell.

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Using alias Command in Linux to Improve Your Efficiency

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.

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

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.

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:

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:

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:

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:

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. On Debian/Ubuntu, updating a server in a single command could be done through an alias such as this one:

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:

Conclusion

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.

Источник

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:

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:

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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