text_editing_101.rst

Text Editing 101

As a sysadmin, and especially as a Linux/Unix sysadmin, you're going to have to get used to not only editing text files, but also efficiently making your way around the command line. Both of these tasks require you to get familiarized and comfortable with the two most common text editors in this space: vi and emacs

A little history

Back when UNIX was just starting to appear on computers that had actual input/output systems (e.g. teletype), interaction with the computer was strictly a text-based affair. The computer would send some data in the form of ASCII characters over a slow telephone link. The user would then hit some keys on the keyboard, which would send back more ASCII characters to the computer, again over the slow telephone link.

Because communication was so slow, UNIX programmers and users wrote their internal tools to be as efficient as possible. Early editors, such as ed, would only let you see one line of text in the file at a time, since the commonly used interface at the time, a teletype, printed on paper and thus there was no concept of "redrawing" or even of a "screen". These early tools later evolved into the more advanced editors like vi and emacs in use today. But these tools retain their UNIX heritage of lean efficiency. Commands are sent usually in single characters, there's no "toolbar", and the editor provides powerful tools to quickly shuttle the cursor around the file quickly, without having to display unrelated text/context in the file.

vi basics

vi was created as an extension to ed. When "modern" terminals (e.g. electronic displays, not teletypes) became common, it made sense to use a "visual" editing mode, where you could see the context of the line you were editing. From ed, you would enter "visual" mode by running :vi -- thus VI was born.

Since then, vi has been written and re-written many many times. But inside, you will still find good ol' ed. In Text Edting 201, you will see how you can still access the very powerful ed features by using the colon (:) command.

There are many versions of vi out there, but the most popular is vim (VI iMproved). Virtually every Linux distribution out there provides vim either by default, or as an easily installable package. vim extends the feature set provided by the POSIX-compliant vi utility in many ways. In the examples below, features that are only present in vim will be noted.

Command and Insert mode

The first thing to understand about how vi works is that it operates in two modes.

Insert mode is when you are actually typing in text. The keys you type while in insert mode are simply dumped into the editor. You exit insert mode by pressing the Esc key.

Command mode is when vi is not in insert mode. When in command mode, the keys you type are interpreted by vi as commands, not as text you wish to put into the file. For example, moving the cursor around the screen is a series of commands, as is writing to a file.

Hello, world!

Before learning anything else, you'll need to know how to do two basic operations, which are best described by working through these steps.

Start vi and edit a new file:

vi helloworld.txt

The editor will start up in command mode. The first thing we want to do is add some text to the file. Press i to enter "insert" mode. You will notice that the editor begins to let you start typing text into the file. Enter some text into the file:

Hello, World!

Now you want to save the contents, so follow these steps:

1. Press Esc to exit insert mode and enter command mode
2. Press : and then w, then Enter. This will write out to the file.
3. The editor remains in command mode, waiting for your next command.

Now you want to exit the editor:

1. Press Esc to exit insert mode (hitting Esc while in command mode does nothing, so it's safe to just hit it for good measure)
2. Press : and then q (quit), then Enter. You will exit vi.

Cursor motion

Now that you know how to open a file, put some text into it, and then exit the editor. The next most important thing to learn is how to move around in the file. While using the arrow keys might work, it's far from optimal, and may not be implemented in strictly POSIX-compliant versions of vi.

When in command mode, you use the h, j, k, and l (ell) keys to move the cursor around:

• h - left
• j - down
• k - up
• l - right

Seems confusing and awkward at first, right? It's actually not. You will quickly learn the motions without having to think about it, and you will be able to move around very fast in the file, without ever having to move your hands from the home row of the keyboard.

In addition to the simple cursor motion commands, there are a few other cursor motion commands that are extremely helpful to know:

• w - move forward one word
• b - move back one word
• 0 - move to the beginning of the line
• $ - move to the end of the line
• /some text - move forward to the next instance of some text
• ?some text - move backward to the next instance of some text
• n - repeat the previous search operation
• :number - Go directly to line number (example: :20 goes to line 20, :0 goes to the top of the file)
• G - Go directly to the bottom of the file

Text insertion commands

vi gives you several options for how you actually want to insert text when you enter insert mode.

• i - insert text at the position of the cursor. The first character you type will appear to the left of where the cursor is
• a - append text at the position of the cursor. The first character you type will appear to the right of where the cursor is
• I - Same as insert, but first moves the cursor to the beginning of the line (equivalent to 0i.
• A - Same as append, but first moves the cursor to the end of the line (equivalent to $a.
• o - Open a new line under the cursor and begin inserting text there
• O - Open a new line above the cursor and begin inserting text there

Text removal commands

When you delete text in vi, you are actually performing a "cut" operation into a buffer. But you don't need to know that at the moment. You will notice that while in insert mode, you can use the backspace and delete keys as expected. This makes insert mode easiy to use, but it's not particularly efficient if you're trying to eliminate a whole paragraph or something from your document. When in command mode, you can issue some commands that remove whole chunks of text:

• x - Delete the character under the cursor
• dd - Delete the line under the cursor
• dG - Delete the current line, and everything else to the bottom of the file
• d:0 - Delete the current line, and everything else to the top of the file
• dw - Delete from the character under the cursor to the beginning of the next word
• NUMdd - Delete NUM lines of text, ex: 10dd deletes 10 lines

Undo and Redo

Now that you know how to add and remove text, you'll inevitably end up making a mistake. Luckily, vi lets you undo the last command or insertion, by going back to command mode and hitting the u key.

In vim (but not strict POSIX vi), you can also press R to redo the last thing you un-did.

Professional Fonts (vim?)

Syntax Highlighting (vim)

Directory navigation (NERDtree)

Edit/Open/Close Files

Edit/Open/Close Buffers (vim)