*usr_41.txt* For Vim version 7.0c. Last change: 2006 Mar 24 VIM USER MANUAL - by Bram Moolenaar Write a Vim script The Vim script language is used for the startup vimrc file, syntax files, and many other things. This chapter explains the items that can be used in a Vim script. There are a lot of them, thus this is a long chapter. |41.1| Introduction |41.2| Variables |41.3| Expressions |41.4| Conditionals |41.5| Executing an expression |41.6| Using functions |41.7| Defining a function |41.8| Lists and Dictionaries |41.9| Exceptions |41.10| Various remarks |41.11| Writing a plugin |41.12| Writing a filetype plugin |41.13| Writing a compiler plugin |41.14| Writing a plugin that loads quickly |41.15| Writing library scripts |41.16| Distributing Vim scripts Next chapter: |usr_42.txt| Add new menus Previous chapter: |usr_40.txt| Make new commands Table of contents: |usr_toc.txt| ============================================================================== *41.1* Introduction *vim-script-intro* *script* Your first experience with Vim scripts is the vimrc file. Vim reads it when it starts up and executes the commands. You can set options to values you prefer. And you can use any colon command in it (commands that start with a ":"; these are sometimes referred to as Ex commands or command-line commands). Syntax files are also Vim scripts. As are files that set options for a specific file type. A complicated macro can be defined by a separate Vim script file. You can think of other uses yourself. Let's start with a simple example: > :let i = 1 :while i < 5 : echo "count is" i : let i += 1 :endwhile < Note: The ":" characters are not really needed here. You only need to use them when you type a command. In a Vim script file they can be left out. We will use them here anyway to make clear these are colon commands and make them stand out from Normal mode commands. Note: You can try out the examples by yanking the lines from the text here and executing them with :@" The output of the example code is: count is 1 ~ count is 2 ~ count is 3 ~ count is 4 ~ In the first line the ":let" command assigns a value to a variable. The generic form is: > :let {variable} = {expression} In this case the variable name is "i" and the expression is a simple value, the number one. The ":while" command starts a loop. The generic form is: > :while {condition} : {statements} :endwhile The statements until the matching ":endwhile" are executed for as long as the condition is true. The condition used here is the expression "i < 5". This is true when the variable i is smaller than five. Note: If you happen to write a while loop that keeps on running, you can interrupt it by pressing CTRL-C (CTRL-Break on MS-Windows). The ":echo" command prints its arguments. In this case the string "count is" and the value of the variable i. Since i is one, this will print: count is 1 ~ Then there is the ":let i += 1" command. This does the same thing as ":let i = i + 1". This adds one to the variable i and assigns the new value to the same variable. The example was given to explain the commands, but would you really want to make such a loop it can be written much more compact: > :for i in range(1, 4) : echo "count is" i :endfor We won't explain how |:for| and |range()| work until later. Follow the links if you are impatient. THREE KINDS OF NUMBERS Numbers can be decimal, hexadecimal or octal. A hexadecimal number starts with "0x" or "0X". For example "0x1f" is decimal 31. An octal number starts with a zero. "017" is decimal 15. Careful: don't put a zero before a decimal number, it will be interpreted as an octal number! The ":echo" command always prints decimal numbers. Example: > :echo 0x7f 036 < 127 30 ~ A number is made negative with a minus sign. This also works for hexadecimal and octal numbers. A minus sign is also used for subtraction. Compare this with the previous example: > :echo 0x7f -036 < 97 ~ White space in an expression is ignored. However, it's recommended to use it for separating items, to make the expression easier to read. For example, to avoid the confusion with a negative number above, put a space between the minus sign and the following number: > :echo 0x7f - 036 ============================================================================== *41.2* Variables A variable name consists of ASCII letters, digits and the underscore. It cannot start with a digit. Valid variable names are: counter _aap3 very_long_variable_name_with_underscores FuncLength LENGTH Invalid names are "foo+bar" and "6var". These variables are global. To see a list of currently defined variables use this command: > :let You can use global variables everywhere. This also means that when the variable "count" is used in one script file, it might also be used in another file. This leads to confusion at least, and real problems at worst. To avoid this, you can use a variable local to a script file by prepending "s:". For example, one script contains this code: > :let s:count = 1 :while s:count < 5 : source other.vim : let s:count += 1 :endwhile Since "s:count" is local to this script, you can be sure that sourcing the "other.vim" script will not change this variable. If "other.vim" also uses an "s:count" variable, it will be a different copy, local to that script. More about script-local variables here: |script-variable|. There are more kinds of variables, see |internal-variables|. The most often used ones are: b:name variable local to a buffer w:name variable local to a window g:name global variable (also in a function) v:name variable predefined by Vim DELETING VARIABLES Variables take up memory and show up in the output of the ":let" command. To delete a variable use the ":unlet" command. Example: > :unlet s:count This deletes the script-local variable "s:count" to free up the memory it uses. If you are not sure if the variable exists, and don't want an error message when it doesn't, append !: > :unlet! s:count When a script finishes, the local variables used there will not be automatically freed. The next time the script executes, it can still use the old value. Example: > :if !exists("s:call_count") : let s:call_count = 0 :endif :let s:call_count = s:call_count + 1 :echo "called" s:call_count "times" The "exists()" function checks if a variable has already been defined. Its argument is the name of the variable you want to check. Not the variable itself! If you would do this: > :if !exists(s:call_count) Then the value of s:call_count will be used as the name of the variable that exists() checks. That's not what you want. The exclamation mark ! negates a value. When the value was true, it becomes false. When it was false, it becomes true. You can read it as "not". Thus "if !exists()" can be read as "if not exists()". What Vim calls true is anything that is not zero. Zero is false. Note: Vim automatically converts a string to a number when it is looking for a number. When using a string that doesn't start with a digit the resulting number is zero. Thus look out for this: > :if "true" < The "true" will be interpreted as a zero, thus as false! STRING VARIABLES AND CONSTANTS So far only numbers were used for the variable value. Strings can be used as well. Numbers and strings are the basic types of variables that Vim supports. The type is dynamic, it is set each time when assigning a value to the variable with ":let". More about types in |41.8|. To assign a string value to a variable, you need to use a string constant. There are two types of these. First the string in double quotes: > :let name = "peter" :echo name < peter ~ If you want to include a double quote inside the string, put a backslash in front of it: > :let name = "\"peter\"" :echo name < "peter" ~ To avoid the need for a backslash, you can use a string in single quotes: > :let name = '"peter"' :echo name < "peter" ~ Inside a single-quote string all the characters are as they are. Only the single quote itself is special: you need to use two to get one. A backslash is taken literally, thus you can't use it to change the meaning of the character after it. In double-quote strings it is possible to use special characters. Here are a few useful ones: \t \n , line break \r , \e \b , backspace \" " \\ \, backslash \ \ CTRL-W The last two are just examples. The "\" form can be used to include the special key "name". See |expr-quote| for the full list of special items in a string. ============================================================================== *41.3* Expressions Vim has a rich, yet simple way to handle expressions. You can read the definition here: |expression-syntax|. Here we will show the most common items. The numbers, strings and variables mentioned above are expressions by themselves. Thus everywhere an expression is expected, you can use a number, string or variable. Other basic items in an expression are: $NAME environment variable &name option @r register Examples: > :echo "The value of 'tabstop' is" &ts :echo "Your home directory is" $HOME :if @a > 5 The &name form can be used to save an option value, set it to a new value, do something and restore the old value. Example: > :let save_ic = &ic :set noic :/The Start/,$delete :let &ic = save_ic This makes sure the "The Start" pattern is used with the 'ignorecase' option off. Still, it keeps the value that the user had set. (Another way to do this would be to add "\C" to the pattern, see |/\C|.) MATHEMATICS It becomes more interesting if we combine these basic items. Let's start with mathematics on numbers: a + b add a - b subtract a * b multiply a / b divide a % b modulo The usual precedence is used. Example: > :echo 10 + 5 * 2 < 20 ~ Grouping is done with braces. No surprises here. Example: > :echo (10 + 5) * 2 < 30 ~ Strings can be concatenated with ".". Example: > :echo "foo" . "bar" < foobar ~ When the ":echo" command gets multiple arguments, it separates them with a space. In the example the argument is a single expression, thus no space is inserted. Borrowed from the C language is the conditional expression: a ? b : c If "a" evaluates to true "b" is used, otherwise "c" is used. Example: > :let i = 4 :echo i > 5 ? "i is big" : "i is small" < i is small ~ The three parts of the constructs are always evaluated first, thus you could see it work as: (a) ? (b) : (c) ============================================================================== *41.4* Conditionals The ":if" commands executes the following statements, until the matching ":endif", only when a condition is met. The generic form is: :if {condition} {statements} :endif Only when the expression {condition} evaluates to true (non-zero) will the {statements} be executed. These must still be valid commands. If they contain garbage, Vim won't be able to find the ":endif". You can also use ":else". The generic form for this is: :if {condition} {statements} :else {statements} :endif The second {statements} is only executed if the first one isn't. Finally, there is ":elseif": :if {condition} {statements} :elseif {condition} {statements} :endif This works just like using ":else" and then "if", but without the need for an extra ":endif". A useful example for your vimrc file is checking the 'term' option and doing something depending upon its value: > :if &term == "xterm" : " Do stuff for xterm :elseif &term == "vt100" : " Do stuff for a vt100 terminal :else : " Do something for other terminals :endif LOGIC OPERATIONS We already used some of them in the examples. These are the most often used ones: a == b equal to a != b not equal to a > b greater than a >= b greater than or equal to a < b less than a <= b less than or equal to The result is one if the condition is met and zero otherwise. An example: > :if v:version >= 700 : echo "congratulations" :else : echo "you are using an old version, upgrade!" :endif Here "v:version" is a variable defined by Vim, which has the value of the Vim version. 600 is for version 6.0. Version 6.1 has the value 601. This is very useful to write a script that works with multiple versions of Vim. |v:version| The logic operators work both for numbers and strings. When comparing two strings, the mathematical difference is used. This compares byte values, which may not be right for some languages. When comparing a string with a number, the string is first converted to a number. This is a bit tricky, because when a string doesn't look like a number, the number zero is used. Example: > :if 0 == "one" : echo "yes" :endif This will echo "yes", because "one" doesn't look like a number, thus it is converted to the number zero. For strings there are two more items: a =~ b matches with a !~ b does not match with The left item "a" is used as a string. The right item "b" is used as a pattern, like what's used for searching. Example: > :if str =~ " " : echo "str contains a space" :endif :if str !~ '\.$' : echo "str does not end in a full stop" :endif Notice the use of a single-quote string for the pattern. This is useful, because backslashes would need to be doubled in a double-quote string and patterns tend to contain many backslashes. The 'ignorecase' option is used when comparing strings. When you don't want that, append "#" to match case and "?" to ignore case. Thus "==?" compares two strings to be equal while ignoring case. And "!~#" checks if a pattern doesn't match, also checking the case of letters. For the full table see |expr-==|. MORE LOOPING The ":while" command was already mentioned. Two more statements can be used in between the ":while" and the ":endwhile": :continue Jump back to the start of the while loop; the loop continues. :break Jump forward to the ":endwhile"; the loop is discontinued. Example: > :while counter < 40 : call do_something() : if skip_flag : continue : endif : if finished_flag : break : endif : sleep 50m :endwhile The ":sleep" command makes Vim take a nap. The "50m" specifies fifty milliseconds. Another example is ":sleep 4", which sleeps for four seconds. Even more looping can be done with the ":for" command, see below in |41.8|. ============================================================================== *41.5* Executing an expression So far the commands in the script were executed by Vim directly. The ":execute" command allows executing the result of an expression. This is a very powerful way to build commands and execute them. An example is to jump to a tag, which is contained in a variable: > :execute "tag " . tag_name The "." is used to concatenate the string "tag " with the value of variable "tag_name". Suppose "tag_name" has the value "get_cmd", then the command that will be executed is: > :tag get_cmd The ":execute" command can only execute colon commands. The ":normal" command executes Normal mode commands. However, its argument is not an expression but the literal command characters. Example: > :normal gg=G This jumps to the first line and formats all lines with the "=" operator. To make ":normal" work with an expression, combine ":execute" with it. Example: > :execute "normal " . normal_commands The variable "normal_commands" must contain the Normal mode commands. Make sure that the argument for ":normal" is a complete command. Otherwise Vim will run into the end of the argument and abort the command. For example, if you start Insert mode, you must leave Insert mode as well. This works: > :execute "normal Inew text \" This inserts "new text " in the current line. Notice the use of the special key "\". This avoids having to enter a real character in your script. If you don't want to execute a string but evaluate it to get its expression value, you can use the eval() function: > :let optname = "path" :let optval = eval('&' . optname) A "&" character is prepended to "path", thus the argument to eval() is "&path". The result will then be the value of the 'path' option. The same thing can be done with: > :exe 'let optval = &' . optname ============================================================================== *41.6* Using functions Vim defines many functions and provides a large amount of functionality that way. A few examples will be given in this section. You can find the whole list here: |functions|. A function is called with the ":call" command. The parameters are passed in between braces, separated by commas. Example: > :call search("Date: ", "W") This calls the search() function, with arguments "Date: " and "W". The search() function uses its first argument as a search pattern and the second one as flags. The "W" flag means the search doesn't wrap around the end of the file. A function can be called in an expression. Example: > :let line = getline(".") :let repl = substitute(line, '\a', "*", "g") :call setline(".", repl) The getline() function obtains a line from the current buffer. Its argument is a specification of the line number. In this case "." is used, which means the line where the cursor is. The substitute() function does something similar to the ":substitute" command. The first argument is the string on which to perform the substitution. The second argument is the pattern, the third the replacement string. Finally, the last arguments are the flags. The setline() function sets the line, specified by the first argument, to a new string, the second argument. In this example the line under the cursor is replaced with the result of the substitute(). Thus the effect of the three statements is equal to: > :substitute/\a/*/g Using the functions becomes more interesting when you do more work before and after the substitute() call. FUNCTIONS *function-list* There are many functions. We will mention them here, grouped by what they are used for. You can find an alphabetical list here: |functions|. Use CTRL-] on the function name to jump to detailed help on it. String manipulation: char2nr() get ASCII value of a character nr2char() get a character by its ASCII value escape() escape characters in a string with a '\' strtrans() translate a string to make it printable tolower() turn a string to lowercase toupper() turn a string to uppercase match() position where a pattern matches in a string matchend() position where a pattern match ends in a string matchstr() match of a pattern in a string stridx() first index of a short string in a long string strridx() last index of a short string in a long string strlen() length of a string substitute() substitute a pattern match with a string submatch() get a specific match in a ":substitute" strpart() get part of a string expand() expand special keywords iconv() convert text from one encoding to another List manipulation: get() get an item without error for wrong index len() number of items in a List empty() check if List is empty insert() insert an item somewhere in a List add() append an item to a List extend() append a List to a List remove() remove one or more items from a List copy() make a shallow copy of a List deepcopy() make a full copy of a List filter() remove selected items from a List map() change each List item sort() sort a List reverse() reverse the order of a List split() split a String into a List join() join List items into a String string() String representation of a List call() call a function with List as arguments index() index of a value in a List max() maximum value in a List min() minimum value in a List count() count number of times a value appears in a List Dictionary manipulation: get() get an entry without an error for a wrong key len() number of entries in a Dictionary has_key() check whether a key appears in a Dictionary empty() check if Dictionary is empty remove() remove an entry from a Dictionary extend() add entries from one Dictionary to another filter() remove selected entries from a Dictionary map() change each Dictionary entry keys() get List of Dictionary keys values() get List of Dictionary values items() get List of Dictionary key-value pairs copy() make a shallow copy of a Dictionary deepcopy() make a full copy of a Dictionary string() String representation of a Dictionary max() maximum value in a Dictionary min() minimum value in a Dictionary count() count number of times a value appears Working with text in the current buffer: byte2line() get line number at a specific byte count line2byte() byte count at a specific line col() column number of the cursor or a mark virtcol() screen column of the cursor or a mark line() line number of the cursor or mark wincol() window column number of the cursor winline() window line number of the cursor cursor() position the cursor at a line/column getline() get a line or list of lines from the buffer setline() replace a line in the buffer append() append line or list of lines in the buffer indent() indent of a specific line cindent() indent according to C indenting lispindent() indent according to Lisp indenting nextnonblank() find next non-blank line prevnonblank() find previous non-blank line search() find a match for a pattern searchpos() find a match for a pattern searchpair() find the other end of a start/skip/end searchpairpos() find the other end of a start/skip/end System functions and manipulation of files: browse() put up a file requester glob() expand wildcards globpath() expand wildcards in a number of directories resolve() find out where a shortcut points to fnamemodify() modify a file name executable() check if an executable program exists filereadable() check if a file can be read filewritable() check if a file can be written to mkdir() create a new directory isdirectory() check if a directory exists getcwd() get the current working directory getfsize() get the size of a file getftime() get last modification time of a file localtime() get current time strftime() convert time to a string tempname() get the name of a temporary file delete() delete a file rename() rename a file system() get the result of a shell command hostname() name of the system readfile() read a file into a List of lines writefile() write a List of lines into a file Buffers, windows and the argument list: argc() number of entries in the argument list argidx() current position in the argument list argv() get one entry from the argument list bufexists() check if a buffer exists buflisted() check if a buffer exists and is listed bufloaded() check if a buffer exists and is loaded bufname() get the name of a specific buffer bufnr() get the buffer number of a specific buffer winnr() get the window number for the current window bufwinnr() get the window number of a specific buffer winbufnr() get the buffer number of a specific window getbufline() get a list of lines from the specified buffer getbufvar() get a variable value from a specific buffer setbufvar() set a variable in a specific buffer getwinvar() get a variable value from a specific window setwinvar() set a variable in a specific window Folding: foldclosed() check for a closed fold at a specific line foldclosedend() like foldclosed() but return the last line foldlevel() check for the fold level at a specific line foldtext() generate the line displayed for a closed fold Syntax highlighting: hlexists() check if a highlight group exists hlID() get ID of a highlight group synID() get syntax ID at a specific position synIDattr() get a specific attribute of a syntax ID synIDtrans() get translated syntax ID History: histadd() add an item to a history histdel() delete an item from a history histget() get an item from a history histnr() get highest index of a history list Interactive: confirm() let the user make a choice getchar() get a character from the user getcharmod() get modifiers for the last typed character input() get a line from the user inputsecret() get a line from the user without showing it inputdialog() get a line from the user in a dialog inputsave() save and clear typeahead inputrestore() restore typeahead Vim server: serverlist() return the list of server names remote_send() send command characters to a Vim server remote_expr() evaluate an expression in a Vim server server2client() send a reply to a client of a Vim server remote_peek() check if there is a reply from a Vim server remote_read() read a reply from a Vim server foreground() move the Vim window to the foreground remote_foreground() move the Vim server window to the foreground Various: type() type of a variable mode() get current editing mode visualmode() last visual mode used hasmapto() check if a mapping exists mapcheck() check if a matching mapping exists maparg() get rhs of a mapping exists() check if a variable, function, etc. exists has() check if a feature is supported in Vim getqflist() list of quickfix errors getloclist() list of location list items cscope_connection() check if a cscope connection exists did_filetype() check if a FileType autocommand was used eventhandler() check if invoked by an event handler getwinposx() X position of the GUI Vim window getwinposy() Y position of the GUI Vim window winheight() get height of a specific window winwidth() get width of a specific window libcall() call a function in an external library libcallnr() idem, returning a number getreg() get contents of a register getregtype() get type of a register setqflist() modify a quickfix list setloclist() modify a location list setreg() set contents and type of a register taglist() get list of matching tags ============================================================================== *41.7* Defining a function Vim enables you to define your own functions. The basic function declaration begins as follows: > :function {name}({var1}, {var2}, ...) : {body} :endfunction < Note: Function names must begin with a capital letter. Let's define a short function to return the smaller of two numbers. It starts with this line: > :function Min(num1, num2) This tells Vim that the function is named "Min" and it takes two arguments: "num1" and "num2". The first thing you need to do is to check to see which number is smaller: > : if a:num1 < a:num2 The special prefix "a:" tells Vim that the variable is a function argument. Let's assign the variable "smaller" the value of the smallest number: > : if a:num1 < a:num2 : let smaller = a:num1 : else : let smaller = a:num2 : endif The variable "smaller" is a local variable. Variables used inside a function are local unless prefixed by something like "g:", "a:", or "s:". Note: To access a global variable from inside a function you must prepend "g:" to it. Thus "g:count" inside a function is used for the global variable "count", and "count" is another variable, local to the function. You now use the ":return" statement to return the smallest number to the user. Finally, you end the function: > : return smaller :endfunction The complete function definition is as follows: > :function Min(num1, num2) : if a:num1 < a:num2 : let smaller = a:num1 : else : let smaller = a:num2 : endif : return smaller :endfunction For people who like short functions, this does the same thing: > :function Min(num1, num2) : if a:num1 < a:num2 : return a:num1 : endif : return a:num2 :endfunction A user defined function is called in exactly the same way as a built-in function. Only the name is different. The Min function can be used like this: > :echo Min(5, 8) Only now will the function be executed and the lines be interpreted by Vim. If there are mistakes, like using an undefined variable or function, you will now get an error message. When defining the function these errors are not detected. When a function reaches ":endfunction" or ":return" is used without an argument, the function returns zero. To redefine a function that already exists, use the ! for the ":function" command: > :function! Min(num1, num2, num3) USING A RANGE The ":call" command can be given a line range. This can have one of two meanings. When a function has been defined with the "range" keyword, it will take care of the line range itself. The function will be passed the variables "a:firstline" and "a:lastline". These will have the line numbers from the range the function was called with. Example: > :function Count_words() range : let n = a:firstline : let count = 0 : while n <= a:lastline : let count = count + Wordcount(getline(n)) : let n = n + 1 : endwhile : echo "found " . count . " words" :endfunction You can call this function with: > :10,30call Count_words() It will be executed once and echo the number of words. The other way to use a line range is by defining a function without the "range" keyword. The function will be called once for every line in the range, with the cursor in that line. Example: > :function Number() : echo "line " . line(".") . " contains: " . getline(".") :endfunction If you call this function with: > :10,15call Number() The function will be called six times. VARIABLE NUMBER OF ARGUMENTS Vim enables you to define functions that have a variable number of arguments. The following command, for instance, defines a function that must have 1 argument (start) and can have up to 20 additional arguments: > :function Show(start, ...) The variable "a:1" contains the first optional argument, "a:2" the second, and so on. The variable "a:0" contains the number of extra arguments. For example: > :function Show(start, ...) : echohl Title : echo "Show is " . a:start : echohl None : let index = 1 : while index <= a:0 : echo " Arg " . index . " is " . a:{index} : let index = index + 1 : endwhile : echo "" :endfunction This uses the ":echohl" command to specify the highlighting used for the following ":echo" command. ":echohl None" stops it again. The ":echon" command works like ":echo", but doesn't output a line break. You can also use the a:000 variable, it is a List of all the "..." arguments. See |a:000|. LISTING FUNCTIONS The ":function" command lists the names and arguments of all user-defined functions: > :function < function Show(start, ...) ~ function GetVimIndent() ~ function SetSyn(name) ~ To see what a function does, use its name as an argument for ":function": > :function SetSyn < 1 if &syntax == '' ~ 2 let &syntax = a:name ~ 3 endif ~ endfunction ~ DEBUGGING The line number is useful for when you get an error message or when debugging. See |debug-scripts| about debugging mode. You can also set the 'verbose' option to 12 or higher to see all function calls. Set it to 15 or higher to see every executed line. DELETING A FUNCTION To delete the Show() function: > :delfunction Show You get an error when the function doesn't exist. FUNCTION REFERENCES Sometimes it can be useful to have a variable point to one function or another. You can do it with the function() function. It turns the name of a function into a reference: > :let result = 0 " or 1 :function! Right() : return 'Right!' :endfunc :function! Wrong() : return 'Wrong!' :endfunc : :if result == 1 : let Afunc = function('Right') :else : let Afunc = function('Wrong') :endif :echo call(Afunc, []) < Wrong! ~ Note that the name of a variable that holds a function reference must start with a capital. Otherwise it could be confused with the name of a builtin function. The way to invoke a function that a variable refers to is with the call() function. Its first argument is the function reference, the second argument is a List with arguments. Function references are most useful in combination with a Dictionary, as is explained in the next section. ============================================================================== *41.8* Lists and Dictionaries So far we have used the basic types String and Number. Vim also supports two composite types: List and Dictionary. A List is an ordered sequence of things. The things can be any kind of value, thus you can make a List of numbers, a List of Lists and even a List of mixed items. To create a List with three strings: > :let alist = ['aap', 'mies', 'noot'] The List items are enclosed in square brackets and separated by commas. To create an empty List: > :let alist = [] You can add items to a List with the add() function: > :let alist = [] :call add(alist, 'foo') :call add(alist, 'bar') :echo alist < ['foo', 'bar'] ~ List concatenation is done with +: > :echo alist + ['foo', 'bar'] < ['foo', 'bar', 'foo', 'bar'] ~ Or, if you want to extend a List directly: > :let alist = ['one'] :call extend(alist, ['two', 'three']) :echo alist < ['one', 'two', 'three'] ~ Notice that using add() will have a different effect: > :let alist = ['one'] :call add(alist, ['two', 'three']) :echo alist < ['one', ['two', 'three']] ~ The second argument of add() is added as a single item. FOR LOOP One of the nice things you can do with a List is iterate over it: > :let alist = ['one', 'two', 'three'] :for n in alist : echo n :endfor < one ~ two ~ three ~ This will loop over each element in List "alist", assigning the value to variable "n". The generic form of a for loop is: > :for {varname} in {listexpression} : {commands} :endfor To loop a certain number of times you need a List of a specific length. The range() function creates one for you: > :for a in range(3) : echo a :endfor < 0 ~ 1 ~ 2 ~ Notice that the first item of the List that range() produces is zero, thus the last item is one less than the length of the list. You can also specify the maximum value, the stride and even go backwards: > :for a in range(8, 4, -2) : echo a :endfor < 8 ~ 6 ~ 4 ~ A more useful example, looping over lines in the buffer: > :for line in getline(1, 20) : if line =~ "Date: " : echo matchstr(line, 'Date: \zs.*') : endif :endfor This looks into lines 1 to 20 (inclusive) and echoes any date found in there. DICTIONARIES A Dictionary stores key-value pairs. You can quickly lookup a value if you know the key. A Dictionary is created with curly braces: > :let uk2nl = {'one': 'een', 'two': 'twee', 'three': 'drie'} Now you can lookup words by putting the key in square brackets: > :echo uk2nl['two'] < twee ~ The generic form for defining a Dictionary is: > { : , ...} An empty Dictionary is one without any keys: > {} The possibilities with Dictionaries are numerous. There are various functions for them as well. For example, you can obtain a list of the keys and loop over them: > :for key in keys(uk2nl) : echo key :endfor < three ~ one ~ two ~ The will notice the keys are not ordered. You can sort the list to get a specific order: > :for key in sort(keys(uk2nl)) : echo key :endfor < one ~ three ~ two ~ But you can never get back the order in which items are defined. For that you need to use a List, it stores items in an ordered sequence. DICTIONARY FUNCTIONS The items in a Dictionary can normally be obtained with an index in square brackets: > :echo uk2nl['one'] < een ~ A method that does the same, but without so many punctuation characters: > :echo uk2nl.one < een ~ This only works for a key that is made of ASCII letters, digits and the underscore. You can also assign a new value this way: > :let uk2nl.four = 'vier' :echo uk2nl < {'three': 'drie', 'four': 'vier', 'one': 'een', 'two': 'twee'} ~ And now for something special: you can directly define a function and store a reference to it in the dictionary: > :function uk2nl.translate(line) dict : return join(map(split(a:line), 'get(self, v:val, "???")')) :endfunction Let's first try it out: > :echo uk2nl.translate('three two five one') < drie twee ??? een ~ The first special thing you notice is the "dict" at the end of the ":function" line. This marks the function as being used from a Dictionary. The "self" local variable will then refer to that Dictionary. Now let's break up the complicated return command: > split(a:line) The split() function takes a string, chops it into white separated words and returns a list with these words. Thus in the example it returns: > :echo split('three two five one') < ['three', 'two', 'five', 'one'] ~ This list is the first argument to the map() function. This will go through the list, evaluating its second argument with "v:val" set to the value of each item. This is a shortcut to using a for loop. This command: > :let alist = map(split(a:line), 'get(self, v:val, "???")') Is equivalent to: > :let alist = split(a:line) :for idx in range(len(alist)) : let alist[idx] = get(self, alist[idx], "???") :endfor The get() function checks if a key is present in a Dictionary. If it is, then the value is retrieved. If it isn't, then the default value is returned, in the example it's '???'. This is a convenient way to handle situations where a key may not be present and you don't want an error message. The join() function does the opposite of split(): it joins together a list of words, putting a space in between. This combination of split(), map() and join() is a nice way to filter a line of words in a very compact way. OBJECT ORIENTED PROGRAMMING Now that you can put both values and functions in a Dictionary, you can actually use a Dictionary like an object. Above we used a Dictionary for translating Dutch to English. We might want to do the same for other languages. Let's first make an object (aka Dictionary) that has the translate function, but no words to translate: > :let transdict = {} :function transdict.translate(line) dict : return join(map(split(a:line), 'get(self.words, v:val, "???")')) :endfunction It's slightly different from the function above, using 'self.words' to lookup word translations. But we don't have a self.words. Thus you could call this an abstract class. Now we can instantiate a Dutch translation object: > :let uk2nl = copy(transdict) :let uk2nl.words = {'one': 'een', 'two': 'twee', 'three': 'drie'} :echo uk2nl.translate('three one') < drie een ~ And a German translator: > :let uk2de = copy(transdict) :let uk2de.words = {'one': 'ein', 'two': 'zwei', 'three': 'drei'} :echo uk2de.translate('three one') < drei ein ~ You see that the copy() function is used to make a copy of the "transdict" Dictionary and then the copy is changed to add the words. The original remains the same, of course. Now you can go one step further, and use your preferred translator: > :if $LANG =~ "de" : let trans = uk2de :else : let trans = uk2nl :endif :echo trans.translate('one two three') < een twee drie ~ Here "trans" refers to one of the two objects (Dictionaries). No copy is made. More about List and Dictionary identity can be found at |list-identity| and |dict-identity|. Now you might use a language that isn't supported. You can overrule the translate() function to do nothing: > :let uk2uk = copy(transdict) :function! uk2uk.translate(line) : return a:line :endfunction :echo uk2uk.translate('three one wladiwostok') < three one wladiwostok ~ Notice that a ! was used to overwrite the existing function reference. Now use "uk2uk" when no recognized language is found: > :if $LANG =~ "de" : let trans = uk2de :elseif $LANG =~ "nl" : let trans = uk2nl :else : let trans = uk2uk :endif :echo trans.translate('one two three') < one two three ~ For further reading see |Lists| and |Dictionaries|. ============================================================================== *41.9* Exceptions Let's start with an example: > :try : read ~/templates/pascal.tmpl :catch /E484:/ : echo "Sorry, the Pascal template file cannot be found." :endtry The ":read" command will fail if the file does not exist. Instead of generating an error message, this code catches the error and gives the user a nice message instead. For the commands in between ":try" and ":endtry" errors are turned into exceptions. An exception is a string. In the case of an error the string contains the error message. And every error message has a number. In this case, the error we catch contains "E484:". This number is guaranteed to stay the same (the text may change, e.g., it may be translated). When the ":read" command causes another error, the pattern "E484:" will not match in it. Thus this exception will not be caught and result in the usual error message. You might be tempted to do this: > :try : read ~/templates/pascal.tmpl :catch : echo "Sorry, the Pascal template file cannot be found." :endtry This means all errors are caught. But then you will not see errors that are useful, such as "E21: Cannot make changes, 'modifiable' is off". Another useful mechanism is the ":finally" command: > :let tmp = tempname() :try : exe ".,$write " . tmp : exe "!filter " . tmp : .,$delete : exe "$read " . tmp :finally : call delete(tmp) :endtry This filters the lines from the cursor until the end of the file through the "filter" command, which takes a file name argument. No matter if the filtering works, something goes wrong in between ":try" and ":finally" or the user cancels the filtering by pressing CTRL-C, the "call delete(tmp)" is always executed. This makes sure you don't leave the temporary file behind. More information about exception handling can be found in the reference manual: |exception-handling|. ============================================================================== *41.10* Various remarks Here is a summary of items that apply to Vim scripts. They are also mentioned elsewhere, but form a nice checklist. The end-of-line character depends on the system. For Unix a single character is used. For MS-DOS, Windows, OS/2 and the like, is used. This is important when using mappings that end in a . See |:source_crnl|. WHITE SPACE Blank lines are allowed and ignored. Leading whitespace characters (blanks and TABs) are always ignored. The whitespaces between parameters (e.g. between the 'set' and the 'cpoptions' in the example below) are reduced to one blank character and plays the role of a separator, the whitespaces after the last (visible) character may or may not be ignored depending on the situation, see below. For a ":set" command involving the "=" (equal) sign, such as in: > :set cpoptions =aABceFst the whitespace immediately before the "=" sign is ignored. But there can be no whitespace after the "=" sign! To include a whitespace character in the value of an option, it must be escaped by a "\" (backslash) as in the following example: > :set tags=my\ nice\ file The same example written as > :set tags=my nice file will issue an error, because it is interpreted as: > :set tags=my :set nice :set file COMMENTS The character " (the double quote mark) starts a comment. Everything after and including this character until the end-of-line is considered a comment and is ignored, except for commands that don't consider comments, as shown in examples below. A comment can start on any character position on the line. There is a little "catch" with comments for some commands. Examples: > :abbrev dev development " shorthand :map o#include " insert include :execute cmd " do it :!ls *.c " list C files The abbreviation 'dev' will be expanded to 'development " shorthand'. The mapping of will actually be the whole line after the 'o# ....' including the '" insert include'. The "execute" command will give an error. The "!" command will send everything after it to the shell, causing an error for an unmatched '"' character. There can be no comment after ":map", ":abbreviate", ":execute" and "!" commands (there are a few more commands with this restriction). For the ":map", ":abbreviate" and ":execute" commands there is a trick: > :abbrev dev development|" shorthand :map o#include|" insert include :execute cmd |" do it With the '|' character the command is separated from the next one. And that next command is only a comment. Notice that there is no white space before the '|' in the abbreviation and mapping. For these commands, any character until the end-of-line or '|' is included. As a consequence of this behavior, you don't always see that trailing whitespace is included: > :map o#include To avoid these problems, you can set the 'list' option when editing vimrc files. PITFALLS Even bigger problem arises in the following example: > :map ,ab o#include :unmap ,ab Here the unmap command will not work, because it tries to unmap ",ab ". This does not exist as a mapped sequence. An error will be issued, which is very hard to identify, because the ending whitespace character in ":unmap ,ab " is not visible. And this is the same as what happens when one uses a comment after an 'unmap' command: > :unmap ,ab " comment Here the comment part will be ignored. However, Vim will try to unmap ',ab ', which does not exist. Rewrite it as: > :unmap ,ab| " comment RESTORING THE VIEW Sometimes you want to make a change and go back to where cursor was. Restoring the relative position would also be nice, so that the same line appears at the top of the window. This example yanks the current line, puts it above the first line in the file and then restores the view: > map ,p ma"aYHmbgg"aP`bzt`a What this does: > ma"aYHmbgg"aP`bzt`a < ma set mark a at cursor position "aY yank current line into register a Hmb go to top line in window and set mark b there gg go to first line in file "aP put the yanked line above it `b go back to top line in display zt position the text in the window as before `a go back to saved cursor position PACKAGING To avoid your function names to interfere with functions that you get from others, use this scheme: - Prepend a unique string before each function name. I often use an abbreviation. For example, "OW_" is used for the option window functions. - Put the definition of your functions together in a file. Set a global variable to indicate that the functions have been loaded. When sourcing the file again, first unload the functions. Example: > " This is the XXX package if exists("XXX_loaded") delfun XXX_one delfun XXX_two endif function XXX_one(a) ... body of function ... endfun function XXX_two(b) ... body of function ... endfun let XXX_loaded = 1 ============================================================================== *41.11* Writing a plugin *write-plugin* You can write a Vim script in such a way that many people can use it. This is called a plugin. Vim users can drop your script in their plugin directory and use its features right away |add-plugin|. There are actually two types of plugins: global plugins: For all types of files. filetype plugins: Only for files of a specific type. In this section the first type is explained. Most items are also relevant for writing filetype plugins. The specifics for filetype plugins are in the next section |write-filetype-plugin|. NAME First of all you must choose a name for your plugin. The features provided by the plugin should be clear from its name. And it should be unlikely that someone else writes a plugin with the same name but which does something different. And please limit the name to 8 characters, to avoid problems on old Windows systems. A script that corrects typing mistakes could be called "typecorr.vim". We will use it here as an example. For the plugin to work for everybody, it should follow a few guidelines. This will be explained step-by-step. The complete example plugin is at the end. BODY Let's start with the body of the plugin, the lines that do the actual work: > 14 iabbrev teh the 15 iabbrev otehr other 16 iabbrev wnat want 17 iabbrev synchronisation 18 \ synchronization 19 let s:count = 4 The actual list should be much longer, of course. The line numbers have only been added to explain a few things, don't put them in your plugin file! HEADER You will probably add new corrections to the plugin and soon have several versions laying around. And when distributing this file, people will want to know who wrote this wonderful plugin and where they can send remarks. Therefore, put a header at the top of your plugin: > 1 " Vim global plugin for correcting typing mistakes 2 " Last Change: 2000 Oct 15 3 " Maintainer: Bram Moolenaar About copyright and licensing: Since plugins are very useful and it's hardly worth restricting their distribution, please consider making your plugin either public domain or use the Vim |license|. A short note about this near the top of the plugin should be sufficient. Example: > 4 " License: This file is placed in the public domain. LINE CONTINUATION, AVOIDING SIDE EFFECTS *use-cpo-save* In line 18 above, the line-continuation mechanism is used |line-continuation|. Users with 'compatible' set will run into trouble here, they will get an error message. We can't just reset 'compatible', because that has a lot of side effects. To avoid this, we will set the 'cpoptions' option to its Vim default value and restore it later. That will allow the use of line-continuation and make the script work for most people. It is done like this: > 11 let s:save_cpo = &cpo 12 set cpo&vim .. 42 let &cpo = s:save_cpo We first store the old value of 'cpoptions' in the s:save_cpo variable. At the end of the plugin this value is restored. Notice that a script-local variable is used |s:var|. A global variable could already be in use for something else. Always use script-local variables for things that are only used in the script. NOT LOADING It's possible that a user doesn't always want to load this plugin. Or the system administrator has dropped it in the system-wide plugin directory, but a user has his own plugin he wants to use. Then the user must have a chance to disable loading this specific plugin. This will make it possible: > 6 if exists("loaded_typecorr") 7 finish 8 endif 9 let loaded_typecorr = 1 This also avoids that when the script is loaded twice it would cause error messages for redefining functions and cause trouble for autocommands that are added twice. MAPPING Now let's make the plugin more interesting: We will add a mapping that adds a correction for the word under the cursor. We could just pick a key sequence for this mapping, but the user might already use it for something else. To allow the user to define which keys a mapping in a plugin uses, the item can be used: > 22 map a TypecorrAdd The "TypecorrAdd" thing will do the work, more about that further on. The user can set the "mapleader" variable to the key sequence that he wants this mapping to start with. Thus if the user has done: > let mapleader = "_" the mapping will define "_a". If the user didn't do this, the default value will be used, which is a backslash. Then a map for "\a" will be defined. Note that is used, this will cause an error message if the mapping already happened to exist. |:map-| But what if the user wants to define his own key sequence? We can allow that with this mechanism: > 21 if !hasmapto('TypecorrAdd') 22 map a TypecorrAdd 23 endif This checks if a mapping to "TypecorrAdd" already exists, and only defines the mapping from "a" if it doesn't. The user then has a chance of putting this in his vimrc file: > map ,c TypecorrAdd Then the mapped key sequence will be ",c" instead of "_a" or "\a". PIECES If a script gets longer, you often want to break up the work in pieces. You can use functions or mappings for this. But you don't want these functions and mappings to interfere with the ones from other scripts. For example, you could define a function Add(), but another script could try to define the same function. To avoid this, we define the function local to the script by prepending it with "s:". We will define a function that adds a new typing correction: > 30 function s:Add(from, correct) 31 let to = input("type the correction for " . a:from . ": ") 32 exe ":iabbrev " . a:from . " " . to .. 36 endfunction Now we can call the function s:Add() from within this script. If another script also defines s:Add(), it will be local to that script and can only be called from the script it was defined in. There can also be a global Add() function (without the "s:"), which is again another function. can be used with mappings. It generates a script ID, which identifies the current script. In our typing correction plugin we use it like this: > 24 noremap