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11.9 Programming Assistance

vim has extensive facilities for both the edit-compile-debug cycle and syntax highlighting.

11.9.1 Edit-Compile Speedup

The facilities in vim were inspired by the "quick fix" mode of the Manx Aztec C compiler for the Amiga. In fact, the vim documentation refers to this feature as "quick fix" mode. The features are quite flexible, allowing you to tailor them to your programming environment (see Table 11.12 ).


Table 11.12: vim Program Development Commands
Command Function
mak [e ] [arguments ]

Run make , based on the settings of several options as described below, then go to the location of the first error.

cf [ile ][! ] [errorfile ]

Read the error file and jump to the first error. With an errorfile , use that file for errors and set the errorfile option to it. The ! forces vim to move to another buffer if the current one has been modified but not saved.

cl [ist ][! ]

List the errors that include a filename. With ! , list all errors.

[count ]cn [ext ][! ]

Display the count th next error that includes a filename. If there are no filenames at all, go to the count th next error.

[count ]cN [ext ][! ]

Display the count th previous error that includes a filename. If there are no filenames at all, go to the count th previous error.

[count ]cp [revious ][! ]
clast [! ] [n ]

Display error n if supplied. Otherwise, display the last error.

crewind [! ] [n ]

Display error n if supplied. Otherwise, display the first error.

cc [! ] [n ]

Displays error n if supplied, otherwise redisplays the current error.

cq [uit ]

Quit with an error code, so that the compiler will not compile the same file again. This is intended primarily for use with the Amiga compiler.

Like elvis , as you move through the errors vim also compensates for changes in the file, so that when you go to the next error, you end up on the correct line.

The vim options that control the :make command are presented in Table 11.13 .


Table 11.13: vim Program Development Options
Option Value Function
shell /bin/sh

The shell to use to execute the command for rebuilding your program.

makeprg make

The program that will actually handle all the recompilation.

shellpipe 2>&1| tee

Whatever is needed to cause the shell to save both standard output and standard error from the compilation in the error file.

makeef /tmp/vim##.err

The name of a file which will contain the compiler output. The ## causes vim to create unique filenames.

errorformat %f:%l:\ %m

A description of what error messages from the compiler look like. This example value is for GCC, the GNU C compiler.

When you execute :make , vim constructs a command by concatenating the various pieces described above. Any arguments you supply are passed to make in the appropriate place. It then echoes this command to your screen. For example, if you type :make -k , you might see something like this:

:!make -k 2>&1| tee /tmp/vim34215.err
...

By using the tee (1) program, the output from make and the compiler is saved in the error file (/tmp/vim34215.err ), and also sent to standard output, in this case your screen.

When the make finishes, vim reads the error file, and goes to the location of the first error. It uses the value of the errorformat option to parse the contents of the error file, in order to find file names and line numbers. (The format of this variable is described in full in :help errorformat .) You can then use the :cc command to see the error messages, and the :cnext command to move to the next error.

11.9.2 Syntax Highlighting

Highlighting in vim is based primarily on colors. To enable syntax highlighting, put syntax on into your .vimrc file. This will cause vim to read the syntax.vim file, which defines the default highlight coloring and then sets things up to use highlighting appropriate to each language.

vim has a very powerful sub-language for defining syntax highlighting. The syntax.txt help file in vim 5.1 that describes it is over 1,500 lines long. Therefore, we won't attempt to give all the details here. Instead, the sample file below should give you some taste for what vim can do. The example consists of portions of the syntax file for Awk:

" Vim syntax file
" Language:	awk, nawk, gawk, mawk
" Maintainer:	Antonio Colombo <antonio.colombo@jrc.org>
" Last change:	1997 November 29

" Remove any old syntax stuff hanging around
syn clear

" A bunch of useful Awk keywords
syn keyword awkStatement        break continue delete exit
...

syn keyword awkFunction         atan2 close cos exp int log rand sin \
                                sqrt srand
...

syn keyword awkConditional      if else
syn keyword awkRepeat           while for do

syn keyword awkPatterns         BEGIN END
syn keyword awkVariables        ARGC ARGV FILENAME FNR FS NF NR
...

" Octal format character.
syn match   awkSpecialCharacter contained "\\[0-7]\{1,3\}"
" Hex   format character.
syn match   awkSpecialCharacter contained "\\x[0-9A-Fa-f]\+"

syn match   awkFieldVars        "\$[0-9]\+"

syn match   awkCharClass        contained "\[:[^:\]]*:\]"
syn match   awkRegExp	contained "/\^"ms=s+1
syn match   awkRegExp	contained "\$/"me=e-1
syn match   awkRegExp	contained "[?.*{}|+]"
...

" Numbers, allowing signs (both -, and +)
" Integer number.
syn match  awkNumber            "[+-]\=\<[0-9]\+\>"
" Floating point number.
syn match  awkFloat             "[+-]\=\<[0-9]\+\.[0-9]+\>"
...

syn match  awkComment	"#.*" contains=awkTodo

if !exists("did_awk_syntax_inits")
  let did_awk_syntax_inits = 1
  " The default methods for highlighting.  Can be overridden later
  hi link awkConditional        Conditional
  hi link awkFunction           Function
  hi link awkRepeat             Repeat
  hi link awkStatement          Statement
  ...
  hi link awkNumber             Number
  hi link awkFloat              Float
  ...

  hi link awkComment            Comment
  ...
endif

let b:current_syntax = "awk"

The file above uses syntax keyword to give names to certain classes of keywords (such as real Awk keywords and built-in functions), and syntax match to give names to regular expressions that match certain kinds of objects (such as numbers). Then the hi link statements link the named classes of objects to the predefined highlighting conventions.

The syntax.vim file predefines the standard conventions, with a number of lines like these:

hi Comment	term=bold ctermfg=Cyan guifg=#80a0ff
hi Constant	term=underline ctermfg=Magenta guifg=#ffa0a0
hi Special	term=bold ctermfg=LightRed guifg=Orange
hi Identifier	term=underline ctermfg=DarkCyan guifg=#40ffff
...

The first argument defines the class, and the rest define what kind of highlighting to do on what kind of terminal. term is for a normal terminal, cterm is for a color terminal (in this case, the ForeGround color), and gui is for vim 's GUI interface.

In vim , the syntax colors are global attributes. Changing the Comment color changes the color for all comments in all windows, no matter what programming language you're editing.

Since the syntax descriptions use attribute linking, you can make language-specific changes. For example, to change the comment color for Awk, you can define attributes for awkComment , like this:

hi awkComment guifg=Green

vim comes with a large number of syntax descriptions for different languages. The coloring for Awk is slightly psychedelic (lots of red and pink), although the coloring for context diffs is actually rather pleasant, as is the color scheme for UNIX mailbox files. The HTML mode is also pretty interesting. Overall, it's quite a lot of fun to use.


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