Vim

Introduction

Vim is a mode-based editor, meaning it has different modes with different behaviors. To use Vim, you switch between modes depending on what you want to do.

It often takes time to get used to this feature. You might ask why we bother having modes in the first place. However, you'll find that, with practice, switching between and using different modes becomes effortless and makes coding much faster.

One note before we begin: when first learning Vim, you'll be tempted to use your mouse and/or the arrow keys. Don't do it. The whole point of using Vim is to "throw away the mouse" — you'll find that, after some practice, using Vim's shortcuts will be more productive.

Getting Vim

Vim is already installed on the instructional machines (i.e. your class account), but it behaves strangely by default. To fix this, type

echo "set nocompatible" > ~/.vimrc

This creates a file in your home directory called .vimrc, which is Vim's configuration file. The .vimrc will contain one line that says set nocompatible, which tells Vim not to be compatible with Vi, Vim's predecessor.

You can also get Vim on your own machines. The download site is here.

Linux

You can use your package manager to install Vim. For Ubuntu, use the apt-get package manager:

sudo apt-get install vim

Macs

OS X comes pre-installed with Vim. If you want the graphical user interface (GUI) version, you can also install MacVim.

Windows

You can find the files to download here. I personally haven't used Vim on Windows before — I suspect it won't be as satisfactory as using it on a UNIX-based machine.

Basics

You can start Vim from the command line just by typing

vim

You can also open a file with Vim:

vim myfile.py

If you are using the text-based version, Vim will take up your entire terminal.

Try typing some words. You'll notice what you type is not rendered on the screen. Vim uses different modes — the mode Vim starts in is called normal mode.

We'll talk more about normal mode in a bit. Students usually find it reassuring to know how to type text first. The mode for regular editing is called insert mode. To switch from normal mode to insert mode, press the letter i. Now try typing — text should be showing up.

To save the file, we need to return to normal mode. To do so, just press the ESC button. Next, type the following:

:w

that is, a colon followed by the letter w (for write). After pressing Enter, your file will be saved.

To exit Vim, go to normal mode and type in

:q

If there are unsaved changes, Vim will prevent you from exiting. You can either save the changes, or if you want to quit without saving, add an exclamation mark after the command:

:q!

And there you have it — a (very, very, very) basic work cycle in Vim!

Note: you might have noticed that pressing the ESC key every time you want to switch back to normal mode takes quite a bit of work, since the ESC key is all the way in the top-left corner of your keyboard. Most people who use Vim remap their ESC key to something else (such as CAPS lock).

Vim Tutor

Vim provides a great built-in tutor to teach you the basics. From the terminal, type

vimtutor

vimtutor is interactive, and gives you a feel for how to use the commands.

Modes

You've already seen insert mode and normal mode. Here is a full list of modes:

There's also an Ex-mode, but we won't talk about it here.

Insert mode

There's not much to say about insert mode. This is where you type like you would with any other text editor.

Most of the time, you'll be switching between normal mode and insert mode. To go from insert to normal, just press ESC.

There are more options to go the other way, to switch from normal to insert:

  • i: start inserting text where the cursor is
  • a: start inserting text right after the cursor
  • I: insert text at the beginning of the line
  • A: insert text at the end of the line
  • o: insert a newline after this line and enter insert mode
  • O: same as lower-case o, but inserts a newline above this line
  • s: deletes the character under the cursor and enters insert mode
  • S: deletes the entire line and enters insert mode

Experiment with each one — I personally use i, A, I, and o the most.

Normal mode

Normal mode is used for navigation and manipulating text. There is a wide variety of commands — the most frequently used are described here.

Remember, to enter normal mode, just press ESC.

In normal mode, the four basic navigation keys are h, j, k, l.

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

While you can use the arrow keys, you'll find (with time) that using hjkl is much faster. Trust me, take the time to learn how to use them — it'll pay off.

There are lots of other navigation keys:

  • words:

    • w: moves forward to the beginning of the next word
    • e: moves forward to the end of the next word
    • b: moves backward to the beginning of the previous word

  • sentences (if applicable)

    • (: moves backward to the beginning of the previous sentence
    • ): moves forward to the beginning of the next sentence

  • paragraphs (if applicable)

    • {: moves backward to the previous paragraph
    • }: moves foward to the next paragraph

  • lines

    • 0: moves to the beginning of the line
    • $: moves to the end of the line

  • screen:

    • CTRL-f: moves an entire "page" down
    • CTRL-b: moves an entire "page" up
    • CTRL-d: moves half a "page" down
    • CTRL-u: moves half a "page" up

  • document-level

    • gg: moves to the top of the document
    • G: moves to the bottom of the document

Undoing changes

The undo key is u — it undoes any modifications to the text. Vim remembers several levels of modifications, so you can keep pressing u to undo further and futher back. You can configure Vim to remember a certain number of levels.

There is also a redo functionality — to undo an undo, press CTRL-r. Again, Vim will remember multiple levels, so you can redo multiple times.

Deleting text

The x command deletes a single character:

  • x: deletes the character right underneath the cursor
  • X: (i.e. SHIFT-x) deletes the character right before the cursor

Using d provides more flexibility and range:

  • dd: deletes the entire line
  • dw: deletes the rest of the current word, starting from the cursor
  • db: deletes the beginning of the current word, starting from cursor
  • dj: deletes this line and the next (2 lines)
  • dk: deletes this line and the previous one (2 lines)
  • D: deletes from the cursor to the end of the line

I use x, dd, dw, and D the most. Of course, play around with the commands and see which ones you're comfortable with.

Note: Vim's delete functionality acts like cut — Vim remembers what you deleted, and you can immediately paste the deleted text.

Yanking text

Yanking is the same as copying text. The primary operator to do so is y:

  • yy: copy the entire line (Y works too)
  • yw: copy the rest of the current word, starting from the cursor
  • yj: copy this line and the next

Note: Yanking and deleting use the same buffer to store text, so they will overwrite each other.

Putting text

In Vim, pasting is called putting text. The primary key to do so is p:

  • p: puts copied text right after the cursor
  • P: (i.e. SHIFT-p) puts copied text right before the cursor

Note that, if you had deleted or yanked an entire line, p will place the line after the current one, and P will place the line before the current one.

Searching

You can initiate a search from normal mode in the following ways:

  • /: starts a forward search — moving to the "next" match will go down the document
  • ?: starts a backward search — moving to the "next" match will go up the document

To search for a string, press one of the keys above, and type in the pattern you want to look for. For example, to search the pattern "class", type

/class

and press enter. To move through matches:

  • n: move to the next match (down if /, up if ?)
  • N: move to the previous match (up if /, down if ?)

Vim's search uses regular expressions, which can come in handy.

Vim has a find-and-replace functionality that you can use in Command mode.

Replacing text

There are two ways to replace text from normal mode:

  • r: replaces the character under the cursor. After pressing r, type the new character, and it will take the place of the old one.
  • R: enters replace mode, which is like pressing the Insert key — it allows you type text, but replaces existing text.

There are lots of other commands in normal mode — look for them on the internet.

Visual mode

Visual mode is used for selecting and highlighting text. There are several ways to switch from normal mode to visual mode:

  • v: enters regular visual mode.
  • V: (i.e. SHIFT-v) highlights entire lines at a time.
  • CTRL-v: "block" visual mode

In each visual mode, you can use normal mode commands for various things:

  • navigation (hjkl, w, etc.)
  • deleting and yanking: d will delete all highlighted text; y will yank the highlighted text. Both then return to normal mode
  • replacing (r): replaces all highlighted characters with a new character (R just deletes the lines of the highlighted text)

In this way, visual mode is useful for moving large bodies of text around. I usually use line-visual mode (V) instead of regular visual mode.

Block visual mode

You'll notice that in regular visual mode, navigating up and down will highlight all text on the line. "Block" visual mode highlights a block of text. The best way to understand it is to try it: from normal mode, type CTRL-v, and then press k to go up — notice that it literally highlights the character above the cursor, without any of the other characters on the line!

Command mode

Vim supports a command line similar to your terminal, except the commands are specific to Vim. To enter command mode from normal mode, press : (the colon). At the bottom of your screen you should see a : appear. Now you can type in a Vim command.

There are tons of Vim commands out there, so we'll only cover a few of the most frequently used ones.

  • :w saves the file. You can also save the file with a name by typing :w filename
  • :q quits Vim. If you have unsaved work, Vim will warn you. To ignore the warning, following the command with a !, like :q!
  • :x saves and quits Vim in one command.

There are commands for doing terminal work:

  • :sh switches to the terminal. This is useful if you need to naviagte through your filesystem or execute some UNIX commands. (Note: :sh opens up a new process)
  • :!unix command executes a single UNIX command (for example, to ls your current directory, type :!ls)

These two commands come in handy; for example, if you want to run a doctest, you can type

:!python3 -m doctest %

and it will run the doctests for the file you are currently working on (the % is a special character in Vim that stands for the name of the current file).

Finally, there's the help utility:

  • :help feature brings up Vim's help documentation on the specified feature

As you use Vim more, you can look up different features and how they work.

Find and replace

As mentioned above, Vim also has a find-and-replace utility. It behaves like the UNIX program sed, so it has regular expression capabilities. To get the full benefit of Vim's sed-like utility, you should take the time to learn both regular expressions and sed.

However, for a simple find-and-replace job, the following command will suffice:

:%s/search pattern/replace pattern/g

The : indicates that this is a Command mode utility. There are a couple of characters to be aware of:

  • %: tells Vim to search the entire document. You can also specify a range of lines. You can even highlight text in Visual mode, and press :s to begin find-and-replace for just the highlighted text
  • s: stands for "substitute." The s should follow the range.
  • /: the forward slashes are delimiters that separate the different fields. Technically, you can replace the / with any character you want, as long as you are consistent — for example, you can do :%s_search pattern_replace pattern_g, but then any unescaped _s in the search and replace patterns will be interpreted as delimeters.
  • g: an optional argument, g stands for "global" and tells Vim to find-and-replace all instances on a line. If you omit the g, Vim will only find-and-replace the first instance of the search pattern on each line.

Some example usage:

# finds all instances of "def" and replaces them with "class"
:%s/def/class/g

# finds all instances of "TODO" and deletes them
:%s/TODO//g

# finds "foo" between lines 403 and 411 and replaces with "bar"
:403,411s/foo/bar/g

Multiple Windows

When working on large projects, it is useful to have multiple files open at the same time. You can always open multiple terminals, but that can get annoying. Vim supports multiple windows.

There are two ways to open windows from command mode:

  • :split opens up a horizontal window. By default, the window contains the same file you are editing, so you can view the same file from different places at the same time.
  • :vsplit is the same as :split, but opens a vertical window

Both split and vsplit can also open up a new file by following the command with the file name

:split filename
:vsplit filename

To navigate between windows, type CTRL-w, followed by one of the hjkl keys.

To close a window, move to that window and quit (type :q).

.vimrc

To configure Vim, you can create a file called a .vimrc (the . hides the file from a normal ls command, but it is still there). Learn more here.