Linux.ie :: vi Tutorial 3

20 August 2003

Quick intro
Firstly I'd like to thank everyone who has mailed me words of appreciation for the two preceding tutorials on ViM that I wrote and also those who have mailed me to ask for more.

Which version of ViM
Some of the features that I am going to describe in this tutorial are onlu available in version 5 of ViM - and even then only if those features were enabled at compile time.
To find out what version you are using, and what the active feature set is, use the :version command. By using this command, vim will display its version number and list the set of features that are available with it. Features named with a '+' in front were enabled at compile time, those with a '-' were not.

The vimrc file
I'm going to explain a bit about the 'vimrc' file. If you already know about it you can move on to the next section.
The vimrc file is a plain text file which is looked at when you start ViM. It is hidden under Linux, in that it is called '.vimrc', and kept in your home directory. The file is used to store commands that you would otherwise have to type in each time that you start up the editor. You can only have one command per line, and these commands can be commented out with a double quote ('"').
For example, most vimrc files will have 'set wrapmargin=1' in them somewhere so that wordwrap is turned on automatically. With the abbreviation command that I covered in the last tutorial you can also use the vimrc file so that ViM will correct your more typical spelling mistakes.

Sourcing files
Over time, your vimrc file could grow to be quite big. It could also get a bit complicated to keep it all in synch - especially if you use vim on more than one machine and a portion of one vimrc is machine specific and you don't want to use an exact copy on the other machine.
There is a nice solution to this scenario, break down the vimrc file into smaller files and use the 'source' command in your vimrc file.
The source command takes the form of 'source '. What it does is read that file and execute the commands that are in it.
Though unlikely, you could end up with a small vimrc file such as:

source ~/.specific.vim
source ~/.fixtypos.vim
source ~/.abbrevs.vim

There's no real requirement to use the '.vim' extension, it will come in handy though if you want them colour-coded when they are edited with syntax highlighting turned on.
On another slightly related topic, you might want to move some of your vim files to somewhere such as /usr/local/vim so they can be used from within all accounts on your machine.

Syntax Highlighting (Colour Coding by a different name).
A very nice thing about version 5 of ViM is that you can tell it to colour code or 'syntax highlight' the text that you are editing. And there's really nothing to it.
If you want to use this to colour code for HTML syntax simply add the folowing line (though you may need to change it slightly) to your vimrc file.

source /usr/share/vim/current/syntax/html.vim

I found out where this html.vim file was through the 'locate' shell command. The corresponding file needed for syntax highlighting C code should be in the same directory as html.vim, and is called c.vim.
Just adding this line to your vimrc file isn't really enough, you have to enable this by typing in the ':syntax on' command. If, for some reason, you need to turn this syntax highlighting off then ':syntax off' will do the trick.
You should only have to do this if the global vimrc file in the /etc directory has the line for syntax highlighting commented out. This seems to be the case by default which really is a shame as the disabled line sources syntax.vim.
This file, syntax.vim, sets things up so that a file with any recognized extension or full filename in the case of some files) will be colour coded by default when you load it into ViM. Needless to say if you want to set up syntax highlighting for yourself you really should 'source' syntax.vim rather than any other file.
There is a whole wealth of files for syntax highlighting that come with ViM. If you are a bit curious of what these files look like you'll find them in /usr/share/vim/current/syntax.
Because syntax highlighting in vim revolves around recognising patterns in the text rather than the context of the text don't be suprised if you see the occasional word incorrectly highlighted. For example, with syntax on, the line

ab liek like

in a file with a '.vim' extension the word 'like' will be displayed in yellow, which shouldn't be the case.
Information on syntax highlighting is available within ViM though the :help syntax command.

Key Mappings
Another way of making things easy for yourself in ViM is to set things up so that one or two keypresses equates to typing in a longer phrase, essentially mapping a keypress to something else.
Some key mappings are already set up in ViM when you start it, you can see what these are by using the ':map' command.
Setting these mapping up is really not that difficult to do and can be really worthwhile. For example, to set up macros to turn syntax highlighting on and off again add these two lines to your vimrc file:

map <F2> <Esc>:syntax on<CR>
map <F3> <Esc>:syntax off<CR>

The first line sets up a mapping against F2 so that it equates to escaping to command mode, typing in :syntax on and pressing Enter. Similarly the second line sets up a mapping so that pressing F3 is the equivalent of typing the command to turn off syntax highlighting.
The documentation for the syntax feature describes a mapping for toggling syntax highlighting on and off:

map <F7> :if exists("syntax_on") <Bar>syntax off <Bar> else <Bar> syntax on <Bar> endif <CR>

If you want to set up a mapping to work on only a visual selection of text then you should use vmap (the 'v' means that the mapping works on visual selections). Similarly, nmap and imap apply to normal mode mappings and insert mode mappings respectively.
For more information, type :help map.

Using ViM for editing C and C++ source files
Apart from the syntax highlighting and the ability to indent your C code through the :%!indent command (which relies on the indent utility being present on your machine), ViM has quite a nice selection of inbuilt commands that you can use when you next use ViM to edit your source code.
If you need to go to the other bracket in a pair of brackets, just press %. Another thing you can do in ViM is type gd with the cursor in the middle of a variable to go to the line where the variable is declared. This willonly work with local variables, gD will do the same with global variables.
Again, there is something quite similar to this for editing header files. Let's say for example that you're editing a .C file, to add in a reference to a new header file that's being included with

include "config.h"

And the next thing that you have to do is edit config.h. The quickest way to load that config.h file into ViM is to place the cursor in the middle of the filename and type 'gf'. Much quicker than ":e config.h', if the file can be found in the path.
If you need to move from one end of a comment, or from one comment to the next, then ]/ and [/ may be of interest to you. The first sequence, namely ]/, will move the cursor to the end of the current comment, or the end of the next comment depending on where it already is. Similarly, [/ will move the cursor to the start of the current comment, or the start of the previous comment, again depending on where the cursor is.
If you need to find out more about the syntax of a keyword, try K in command mode.
More information is available from within ViM, by using the :help C-editing command.

Links
ViM website.
ViM reference card. (originally at http://www.math.fu-berlin.de/~guckes/vim/vim-3.0.refcard.html, 'brought back' by web.archive.org)
Tutorial #1
Tutorial #2
Tutorial #3
Tutorial #4