Here is a quick tutorial for people unfamiliar with text editors in UNIX.  If you are just getting started with the Terminal in OS X, you probably need to create your .bash_profile and such, so that you can keep your settings upon logging out of the shell.  I will show you how to create this file in a text editor called vim, which stands for vi IMproved.

Vim is  a very powerful text editor, and if you have any experience in UNIX at all, you probably were shown pico, which is easier to use at first due to some of the commands being shown at the bottom of the screen as you work in pico’s buffer.  In pico, there is no separation from command or input modes, also making it a bit less confusing.  The buffer simply means what is shown on your screen, not yet written to disk.  While a GUI text editor such as Microsoft Word or Apple’s Pages do not tell you that you are working in a buffer input mode, technically it is the same thing.  If they crash, you lose what you changed if it was not saved prior to the crash.

Vim is a little obscure, yet extremely functional.  You start vim by typing vi or vim at the bash prompt in Terminal.  Terminal is located in your ~/Applications/Utilities folder by default on OS X.  When it opens, you are by default in command mode.  Vim shows you this startup screen, which has a bunch of tildes (~) on the left-hand side, and some version information in the center:

vim Startup Screen OS X Snow Leopard

If you type something in, the startup screen goes away and the first tilde also disappears.  The tilde characters simply clarify lines in the buffer.  They will not print, they are just there showing you where the next lines are.  Once started, you are by default in Vim’s command mode.  If you type vim testfile.txt at the bash prompt, vim will open the file testfile.txt in whichever directory you are currently in.  If testfile.txt doesn’t exist, vim will create the file and open into the edit buffer for you, skipping the welcome screen:

Vim Buffer

As shown in the screenshot (click to enlarge it, as with all screenshots on this blog), the buffer is in INSERT mode.  By default, no matter what file you open or create, vim starts in command mode.  It doesn’t ever show —COMMAND— at the bottom of the screen.  Vim lets you know you aren’t in command mode by telling you that you are in INSERT mode.

To get back into command mode, which is where you will end up saving files to disk, changing the contents of vim’s 26 named buffers (consider them like the clipboard in a GUI text editor), moving around the screen, deleting lines, etc.  Anything you want to do with the file besides type in text will generally be done in command mode. Let’s save this file now, so you can see how it works to get in and out of command mode.

First, hit the ESC key.  On almost every keyboard ever, this will be the key  at the very top-left corner of the keyboard.  You should no longer see –INSERT– at the bottom of the Terminal window.  Now type the following command, without the quotes:  ”:w testfile.txt“.  See screenshot below:

Write Command

File Saved

You can see at the bottom of the Terminal window that the write command was successful.  You also see that three lines were written containing a total of 138 characters.  You can verify the file was written by typing (again, without quotes) “:q“, and hit enter.  This quits vim.  At the bash prompt, type “ls” and hit enter.  You should see your new file in the list of the directory.  To remove (delete) the file, type “rm testfile.txt” and hit enter.

Now to create your .bash_profile, so you can save certain settings.  When Terminal starts, it will read this file to load alias information, screen settings and such, if they are explained in this file.  As you become more familiar with the Terminal and start to have preferences for certain things, i.e., showing hidden files when you get a list of a directory, you may want to create an alias for the ls command so it shows them by “default” because of your .bash_profile.

First, navigate to your home directory if you are not there now.  You do this by typing the command “cd ~” at the bash prompt and hitting enter.  Terminal will show your computer name, followed by your present working directory, and yourusername$, which is the bash prompt.  You should see something like this:

Bash Prompt

Create your empty .bash_profile by typing “vim .bash_profile”  and hitting enter.  We will create a simple alias and save the profile.  Then we will quit Terminal, restart it and verify the alias still works.

Alias in Profile

By default, the alias wouldn’t work again after you quit Terminal.  If it is in your profile, it will work when you open a new Terminal, such is the point of having a profile.  To type in what I show above, press the letter “i“ on your keyboard to put you in insert mode.  Then type the following exactly:

dirA=”ls -lia”

Hit the ESC key, and type: “:w” to save the file.  Now type “:q” to exit vim and return to the bash prompt.  You can verify the file was written and it’s contents by typing “cat .bash_profile” and hitting enter:

Verify File Was Written

Now quit and re-open Terminal.  You should now be able to get a detailed list of your directory, showing hidden files, by typing dirA and hitting enter:

Working dirA Alias

Next time I will show you how to navigate through text, delete lines and add or retrieve lines to and from the named buffers.  If there are certain things you would like to learn about Terminal or vim, please leave comments below.  Please also let me know if any of this could be better clarified, as I check my comments often and will respond promptly.  Thanks for reading!