You almost certainly have speed dial set up on your home, office and mobile phone. It saves time, ensures against a failing memory and allows you to work smarter.

Devotees of the command line don’t have to be left out in the cold. One of the crown jewels of GNU/Linux is that every user, be he ne’er so base, has at his or her fingertips the kind of power of which even Caligula could not dream. Alright, I’m exaggerating—a little.

GNU/Linux comes with many commands and you use them every time you open a console and interact with it through the shell. The Bash shell (often described as the great grandaddy of all shells or, less flatteringly, as “an historical wart on the Bourne shell”) comes as standard with virtually every version of GNU/Linux and there are others too: Fish, Korn and Zsh. Whether you are listing file contents, configuring your wireless card, copying, deleting or moving files or appending arguments to built-in commands you are utilizing those features.

The built-in command I want to look at is alias. (If you want to be technical, alias has been defined as a “parameterless macro” and is not to be confused with IP aliases, a process for adding more than one IP address to a network interface.) It is a perfect example of a command that is simple yet useful and its use is restricted only by your knowledge of the Unix commands and the capacity of your imagination to exploit it. It is probably at this point that you might want to sit down and think about working faster by working smarter. In short it’s time to get out your pencil and paper and start making a list of all of those commands (and composites thereof) that you use most frequently and see if you can’t make them more compact. In the process you will not only work more efficiently; you will have increased your knowledge of the GNU/Linux commands and file system.

You have mail. You also have aliases

Yes you do. You didn’t install them but they’re there. After you grabbed, burned and booted your chosen distro version they are on your hard drive, but what are they and where they are is the question. So what exactly is an alais? Well, it has exactly the same meaning as it does in the everyday world. If the local bobby (or cop for those in the US) was on your trail you might want to change your name in order to disguise your identity. In the shell world there is no such sinister criminal intent. The purpose is not to deceive but to substitute and shorten.

Where are your default aliases? As ever, it depends on what version of GNU/Linux you are using. It could be in one of three places: .bashrc, .bash_aliases or .profile. Mine is in /etc/bashrc, which means, incidentally, that it is available globally. The default install was fairly spartan and includes only the first four aliases. The rest are my own post-install additions (figure 1).

Figure 1: Location of aliases in .bashrc

Creating an alias

So, when you type ls you are already using a built-in alias and your files in any given directory will be displayed, but you might find this a little underpowered. What if you want to list all your hidden files and file permissions? You could type ls -alp and that will do the trick, but by configuring it as an alias you will save time and typing if it is frequently used. To do this, give your alias a name. Clearly, the name needs to be contextual and meaningful to you and above all, it should be short. If you decide on a long name you have defeated the whole purpose of creating an alais in the first place! If you type: alias long="ls -alp" your alias is created. (Note that you cannot have an equals sign in your alias name.) Two points however: first, you can use single or double quotes when creating an alias. Single quotes will save having to select the Shift key and second, you have just made an alias but as you will see the task is not finished just yet.

Make your aliases stick

If I open up a console and make an alias like the one above, it will be available for immediate use. But, if I log out or power down, when I restart and type that name the console will return the classic error message: command not found. Why is that? Simple. Aliases created in a shell will not survive across a reboot and an alias created in one shell will not work in another shell. Here is what I get when I type alias without arguments in my default Bash shell (see figure 2):

Figure 2: List of aliases in the default shell

If I now open a session of the Korn shell in the console (by typing ksh) and then attempt to list all my aliases, I get what is shown in figure 3.

Figure 3: Aliases in bash and korn

You can see the difference. However, what you are really interested in is persistent aliases across a reboot regardless of the shell you are using. For this you need to add them permanently in one of the three files listed above. You will need to do this a root, so it might be a good idea to back up those files just in case over zealous or careless keying drops you into a whole world of pain and hurt. To make your new aliases reload the easy way just type . .bashrc or . .bash_aliases if that is where they are on your system. Note that this is a dot (“.”) followed by a space and another dot and the file name. The perceptive amongst you will have worked out that hand-knitting aliases one at a time is a rather tedious business and it might be a good idea to make a list of all the shortcuts you want and key them all in at one pass.