Monday, 17 May 2010

Going further with environment variables

First of all, I apologise for how long it's taken to get round to this (merely days away from being a full year) but I've been busy! I was frantically busy at work for much of the last year, and have my own web development studies to deal with too, so I've only just gotten around to doing this post. Hopefully I should be able to maintain a better frequency of posts in future!

Last time I explained a bit about how environment variables work. Now we'll get to use them a little. For instance, say you want to set up a shortcut to a specific folder called mystuff to make it easy to get to. Well, you can easily set up an environment variable to hold the path to that folder. Just enter something like this:

export mystuff=/home/user/my/stuff
This will set mystuff up as a local variable that you can call at any time in the same way you'd refer to it normally, like this:

cd $mystuff
Note the dollar sign is only used when calling it, not when setting it.

If you want to set variables permanently, just add them to the .profile file in your home directory. Then, when you next start up a shell, it will automatically load these settings.

There's a number of different settings you can add to customise your bash shell. For instance, the other day I added this to my .profile so that Vim was set as my text editor when using Subversion:

export SVN_EDITOR=/usr/bin/vim

I also added the following to my shell account at (who, incidentally are hands down the best shell account providers I have ever found, and I recommend) so I could use Vim in colour, even over SSH:
export TERM=xterm-256color
There's a huge range of settings you can change to customise your bash shell, so I won't attempt to cover them all. Instead, I'll refer you to the guide in the Ubuntu documentation. A few I will mention, however, are PAGER (typically /usr/bin/less), EDITOR (the default text editor, you can set it to /usr/bin/vim, /usr/bin/emacs, or /usr/bin/nano, or any other CLI editor you want), VISUAL (the visual editor, normally /usr/bin/gedit, although may be different on Kubuntu or Xubuntu), or BROWSER (pretty much what you'd expect).

Now, a related subject to environment variables is aliases. These are handy shortcuts you can write for commonly used commands, and can be a great timesaver. For instance, if you often connect to a specific host via ssh, you can write an alias for it. To set up an alias, just enter something like the following:

alias example="ssh user@server"

Now, just enter example, on its own, into the shell, and it will run the command. But, of course, this is only temporary. To make it permanent, set up a file in your home directory called .bash_aliases and add the alias you want to set up to it. Once you've done that, every time you start a new shell, all the aliases you've defined in the file will be available to you!

I hope this has given you some idea of how to customise your bash shell to your own liking and improve your workflow in the process!

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