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Vim Tips

I collected below some tips on vim that I find helpful.

Configuration

You can configure your vim by putting your configuration options and scripts in the ~/.vimrc file (a hidden file named .vimrc in your home directory). This file will be loaded whenever you starts vim.

Help

In vim, the command :help <topic> shows help about a particular topic in vim. Example, :help backup.

Backup Files

You can ask vim to automatically backup files that you edit. This has been a life saver for me in multiple occasions.

In your ~/.vimrc file,

set backup=on

will cause a copy of your file to be save with suffix ~ appended to its name everytime you save.

I prefer not to clutter my working directory, so I set

set backupdir=~/.backup

and create a directory named ~/.backup to store my backup files.

The settings above are the default in your cs2030-i account. So if you made changes to a file that you regreted on cs2030-i, or if accidentally deleted a file, you can check under ~/.backup to see if the backup can save you.

Undo

Since we are on the topic of correcting mistakes, u in command mode undo your changes. Prefix it with a number $n$ to undo $n$ times. If you regreted your undo, <CTRL-R> will redo.

Syntax Highlighting

If for some reasons, syntax highlighting is not on by default, add this to your ~/.vimrc:

syntax on

Ruler and Numbers

If you prefer to show the line number you are on and the column number you are on, adding the commands to ~/.vimrc

set ruler

will display the line number and the column number on the lower right corner.

You can also add

set number

to label each line with a line number.

Jumping to a Line

If the compiler tells you there is an error on Line $x$, you can issue :<x> to jump to Line $x$. For instance, :40 will go to Line 40.

Navigation

• w jump to the beginning of the next word
• b jump to the beginning of the previous word (reverse of w)
• e jump to the end of the word (or next word when pressed again)
• f + char: search forward in the line and sit on the next matching char
• t + char: search forward in the line and sit on one space before the matching char
• <CTRL-d> jump forward half page
• <CTRL-u> jump backward half page
• $ jump to end of line
• 0 jump to the beginning of the line
• % jump between matching parentheses

Navigation + Editing

vim is powerful because you can combine operations with navigation. For instance c to change, d to delete, y to yank (copy). Since w is the navigation command to move over the current word, combining them we get:

• cw change the current word (delete the current word and enter insert mode)
• dw delete the current word
• yw yank the current word (copy word into buffer)

Can you guess what df), dt), c$, y0 do?

If you repeat the operation c, d, and y, it applies to the whole line, so:

• cc change the whole line
• dd delete the whole line
• yy yank the whole line

You can add a number before an operation to specify how many times you want to repeat an operation. So 5dd deletes 5 lines, 5dw deletes 5 words, etc.

See the article Operator, the True Power of Vim for more details.

Other Editing Operations

• A jump to end of line and enter insert mode
• o open next line and enter insert mode
• O open previous line and enter insert mode

Search and Replace in vim

:%s/oldWord/newWord/gc 

: enters the command mode. % means apply to the whole document, s means substitute, g means global (otherwise, only the first occurance of each line is replaced). c is optional -- adding it cause vim to confirm with you before each replacement

Commenting blocks of code

Sometimes we need to comment out a whole block of code in Java for testing purposes. There are several ways to do it in vim:

• Place the cursor on the first line of the block of code you want to comment.
• 0 to jump to the beginning of the line
• <CTRL-v> enter visual block mode
• Use arrow key to select the block of code you want to comment.
• I to insert at the beginning of the line (here, since we already selected the block, we will insert at the beginning of every selected)
• // to insert the Java comment character (you will see it inserted in the current line, but don't worry)
• <ESC> <ESC> to escape from the visual code and to insert the comment character for the rest of the lines.

To uncomment,

• Place the cursor on the first line of the block of code you want to comment.
• 0 to jump to the beginning of the line
• <CTRL-v> enter block visual mode
• Use arrow key to select the columns of text containing //
• x to delete them

Shell Command

If you need to issue a shell command quickly, you don't have to exit vim, run the command, and launch vim again. You can use !,

:!<command>

will issue the command to shell. E.g.,

:!ls

You can use this to compile your current file, without exiting vim.

:!javac %

Abbreviation

You can use the command ab to abbreviate frequently typed commands. E.g., in your ~/.vimrc,

ab Sop System.out.println("

Now, when you type Sop, it will be expanded into System.out.println("

Auto-Completion

You can <CTRL-P> to auto-complete. By default, the auto-complete dictionary is based on text in your current editing buffers. This is a very useful keystroke saver for long function and variable names.

Auto-Indent the Whole File

You can gg=G in command mode to auto-indent the whole file. gg is the command to go to the beginning of the file. = is the command to indent. G is the command to go to the end of the file.

Swapping Lines

Sometimes you want to swap the order of two lines of code, in command mode, ddp will do the trick. dd deletes the current line, p paste it after the current line, in effect swapping the order of the two lines.

Goto File

Place your cursor on the name of a class (e.g., Event), then in command mode, issue the gf command (goto file). vim will open Event.java. You can set the path to load files from directories other than the current directory. "Ctrl-^" will get out and back to the previous file.

Syntax and Style Checker

I use syntastic to check for style and syntax whenever I save a file. syntastic is a vim plugin.

My .vimrc configuration file contains the following:

"For syntastic
set laststatus=2
set statusline+=%#warningmsg#
set statusline+=%{SyntasticStatuslineFlag()}
set statusline+=%*

let g:syntastic_always_populate_loc_list = 1
let g:syntastic_auto_loc_list = 1
let g:syntastic_check_on_open = 1
let g:syntastic_check_on_wq = 0
let g:syntastic_java_checkers = [ "checkstyle", "javac" ]
let g:syntastic_java_checkstyle_classpath = "~cs2030/bin/checkstyle-8.2-all.jar"
let g:syntastic_java_checkstyle_conf_file = "~cs2030/bin/cs2030_checks.xml"

The last two lines refer to checkstyle tool and its configuration file available from ~cs2030/bin on the host cs2030-i.comp.nus.edu.sg.

Splitting vim's Viewport

• :sp file.java splits the vim window horizontally
• :vsp file.java splits the vim window vertically
• Ctrl-w Ctrl-w moves between the different vim viewports