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---
language: Vimscript
filename: learnvimscript.md
contributors:
- ["HiPhish", "http://hiphish.github.io/"]
---
## Introduction
Vim script (also called VimL) is the subset of Vim's ex-commands which supplies
a number of features one one would expect from a scripting language, such as
values, variables, functions or loops. Always keep in the back of your mind
that a Vim script file is just a sequence of ex-commands. It is very common for
a script to mix programming-language features and raw ex-commands.
You can run Vim script directly by entering the commands in command-mode (press
`:` to enter command-mode), or you can write them to a file (without the
leading `:`) and source it in a running Vim instance (`:source path/to/file`).
Some files are sourced automatically as part of your configuration (see `:h
startup`). This guide assumes that you are familiar with ex-commands and will
only cover the scripting. Help topics to the relevant manual sections are
included.
See `:h usr_41.txt` for the official introduction to Vim script. A comment is
anything following an unmatched `"` until the end of the line, and `|`
separates instructions (what `;` does in most other languages).
```vim
" This is a comment
" The vertical line '|' (pipe) separates commands
echo 'Hello' | echo 'world!'
" Putting a comment after a command usually works
pwd " Displays the current working directory
" Except for some commands it does not; use the command delemiter before the
" comment (echo assumes that the quotation mark begins a string)
echo 'Hello world!' |" Displays a message
" Line breaks can be escaped by pacing a backslash as the first non-whitespace
" character on the *following* line. Only works in script files, not on the
" command line
echo " Hello
\ world "
echo [1,
\ 2]
echo {
\ 'a': 1,
\ 'b': 2
\}
```
## Types
For an overview of types see `:h E712`. For an overview of operators see
`:h expression-syntax`
### Numbers
See `:h expr-number`
```vim
echo 123 |" Decimal
echo 0b1111011 |" Binary
echo 0173 |" Octal
echo 0x7B |" Hexadecimal
echo 123.0 |" Floating-point
echo 1.23e2 |" Floating-point (scientific notation)
```
Note that an *integer* number with a leading `0` is in octal notation. The
usual arithmetic operations are supported.
```vim
echo 1 + 2 |" Addition
echo 1 - 2 |" Subtraction
echo - 1 |" Negation (unary minus)
echo + 1 |" Unary plus (does nothing really, but still legal)
echo 1 * 2 |" Multiplication
echo 1 / 2 |" Division
echo 1 % 2 |" Modulo (remainder)
```
### Booleans
See `:h Boolean`
The number 0 is false, every other number is true. Strings are implicitly
converted to numbers (see below). There are two pre-defined semantic constants.
```vim
echo v:true |" Evaluates to 1 or the string 'v:true'
echo v:false |" Evaluates to 0 or the string 'v:false'
```
Boolean values can result from comparison of two objects.
```vim
echo x == y |" Equality by value
echo x != y |" Unequality
echo x > y |" Greater than
echo x >= y |" Greater than or equal
echo x < y |" Smaller than
echo x <= y |" Smaller than or equal
echo x is y |" Instance identity (lists and dictionaries)
echo x isnot y |" Instance non-identity (lists and dictionaries)
" Strings are compared based on their alphanumerical ordering
" echo 'a' < 'b'. Case sensitivity depends on the setting of 'ignorecase'
" Explicit case-sensitivity is specified by appending '#' (match case) or '?'
" (ignore case) to the operator. Prefer explicity case sensitivity when writing
" portable scripts.
echo 'a' < 'B' | " True or false depending on 'ignorecase'
echo 'a' <? 'B' | " True
echo 'a' <# 'B' | " False
" Regular expression matching
echo "hi" =~ "hello" |" Regular expression match, uses 'ignorecase'
echo "hi" =~# "hello" |" Regular expression match, case sensitive
echo "hi" =~? "hello" |" Regular expression match, case insensitive
echo "hi" !~ "hello" |" Regular expression unmatch, use 'ignorecase'
echo "hi" !~# "hello" |" Regular expression unmatch, case sensitive
echo "hi" !~? "hello" |" Regular expression unmatch, case insensitive
```
Boolean operations are possible.
```vim
echo v:true && v:false |" Logical AND
echo v:true || v:false |" Logical OR
echo ! v:true |" Logical NOT
echo v:true ? 'yes' : 'no' |" Ternary operator
```
### Strings
See `:h String`
An ordered zero-indexed sequence of bytes. The encoding of text into bytes
depends on the option `:h 'encoding'`.
```vim
" Literal constructors
echo "Hello world\n" |" The last two characters stand for newline
echo 'Hello world\n' |" The last two characters are literal
echo 'Let''s go!' |" Two single quotes become one quote character
```
Single-quote strings take all characters are literal, except two single quotes,
which are taken to be a single quote in the string itself. See `:h expr-quote`
for all possible escape sequences.
```
" String concatenation
" The .. operator is preferred, but only supported in since Vim 8.1.1114
echo 'Hello ' . 'world' |" String concatenation
echo 'Hello ' .. 'world' |" String concatenation (new variant)
" String indexing
echo 'Hello'[0] |" First byte
echo 'Hello'[1] |" Second byte
echo 'Hellö'[4] |" Returns a byte, not the character 'ö'
" Substrings (second index is inclusive)
echo 'Hello'[:] |" Copy of entire string
echo 'Hello'[1:3] |" Substring, second to fourth byte
echo 'Hello'[1:-2] |" Substring until second to last byte
echo 'Hello'[1:] |" Substring with starting index
echo 'Hello'[:2] |" Substring with ending index
echo 'Hello'[-2:] |" Substring relative to end of string
```
A negative index is relative to the end of the string. See `:h
string-functions` for all string-related functions.
### Lists
See `:h List`
An ordered zero-indexed heterogeneous sequence of arbitrary Vim script objects.
```vim
" Literal constructor
echo [] |" Empty list
echo [1, 2, 'Hello'] |" List with elements
echo [1, 2, 'Hello', ] |" Trailing comma permitted
echo [[1, 2], 'Hello'] |" Lists can be nested arbitrarily
" List concatenation
echo [1, 2] + [3, 4] |" Creates a new list
" List indexing, negative is relative to end of list (:h list-index)
echo [1, 2, 3, 4][2] |" Third element
echo [1, 2, 3, 4][-1] |" Last element
" List slicing (:h sublist)
echo [1, 2, 3, 4][:] |" Shallow copy of entire list
echo [1, 2, 3, 4][:2] |" Sublist until third item (inclusive)
echo [1, 2, 3, 4][2:] |" Sublist from third item (inclusive)
echo [1, 2, 3, 4][:-2] |" Sublist until second-to-last item (inclusive)
```
All slicing operations create new lists. To modify a list in-place use list
functions (`:h list-functions`) or assign directly to an item (see below about
variables).
### Dictionaries
See `:h Dictionary`
An unordered sequence of key-value pairs, keys are always strings (numbers are
implicitly converted to strings).
```vim
" Dictionary literal
echo {} |" Empty dictionary
echo {'a': 1, 'b': 2} |" Dictionary literal
echo {'a': 1, 'b': 2, } |" Trailing comma permitted
echo {'x': {'a': 1, 'b': 2}} |" Nested dictionary
" Indexing a dictionary
echo {'a': 1, 'b': 2}['a'] |" Literal index
echo {'a': 1, 'b': 2}.a |" Syntactic sugar for simple keys
```
See `:h dict-functions` for dictionary manipulation functions.
### Funcref
See `:h Funcref`
Reference to a function, uses the function name as a string for construction.
When stored in a variable the name of the variable has the same restrictions
as a function name (see below).
```vim
echo function('type') |" Reference to function type()
echo funcref('type') |" Reference by identity, not name
echo {x -> x * x} |" Anonymous function
echo function('substitute', ['hello']) |" Partial function
```
A lambda (`:h lambda`) is an anonymous function; it can only contain one
expression in its body, which is also its implicit return value.
### Regular expression
See `:h regular-expression`
A regular expression pattern is generally a string, but in some cases you can
also use a regular expression between a pair of delimiters (usually `/`, but
you can choose anything).
```vim
" Substitute 'hello' for 'Hello'
substitute/hello/Hello/
```
## Implicit type conversions
Strings are converted to numbers, and numbers to strings when necessary. A
number becomes its decimal notation as a string. A string becomes its numerical
value if it can be parsed to a number, otherwise it becomes zero.
```vim
echo "1" + 1 |" Number
echo "1" .. 1 |" String
echo "0xA" + 1 |" Number
" Strings are treated like numbers when used as booleans
echo "true" ? 1 : 0 |" This string is parsed to 0, which is false
```
## Variables
Variables are bound within a scope; if no scope is provided a default is chosen
by Vim. Use `:let` and `:const` to bind a value and `:unlet` to unbind it.
```vim
let b:my_var = 1 |" Local to current buffer
let w:my_var = 1 |" Local to current window
let t:my_var = 1 |" Local to current tab page
let g:my_var = 1 |" Global variable
let l:my_var = 1 |" Local to current function (see functions below)
let s:my_var = 1 |" Local to current script file
let a:my_arg = 1 |" Function argument (see functions below)
" The Vim scope is read-only
echo v:true |" Special built-in Vim variables (:h v:var)
" Access special Vim memory like variables
let @a = 'Hello' |" Register
let $PATH='' |" Environment variable
let &textwidth = 79 |" Option
let &l:textwidth = 79 |" Local option
let &g:textwidth = 79 |" Global option
" Access scopes as dictionaries (can be modified like all dictionaries)
" See the :h dict-functions, especially get(), for access and manipulation
echo b: |" All buffer variables
echo w: |" All window variables
echo t: |" All tab page variables
echo g: |" All global variables
echo l: |" All local variables
echo s: |" All script variables
echo a: |" All function arguments
echo v: |" All Vim variables
" Constant variables
const x = 10 |" See :h :const, :h :lockvar
" Function reference variables have the same restrictions as function names
let IsString = {x -> type(x) == type('')} |" Global: capital letter
let s:isNumber = {x -> type(x) == type(0)} |" Local: any name allowed
```
When omitted the scope `g:` is implied, except in functions, there `l:` is
implied.
### Multiple value binding (list unpacking)
```vim
" Assign values of list to multiple variables (number of items must match)
let [x, y] = [1, 2]
" Assign the remainer to a rest variable (note the semicolon)
let [mother, father; children] = ['Alice', 'Bob', 'Carol', 'Dennis', 'Emily']
```
## Flow control
### Conditional
Conditions are set between `if` and `endif`. They can be nested.
```vim
if condition
echo 'First condition'
elseif another_condition
echo 'Second condition'
else
echo 'Fail'
endif
```
### Loops
Two types of loops: `:for` and `:while`. Use `:continue` to skip to the next
iteration, `:break` to break out of the loop.
#### For-loop
For-loops iterate over lists and nothing else. If you want to iterate over
another sequence you need to use a function which will create a list.
```vim
" Iterate over a list
for person in ['Alice', 'Bob', 'Carol', 'Dennis', 'Emily']
echo 'Hello ' .. person
endfor
" Iterate over a nested list by unpacking it
for [x, y] in [[1, 0], [0, 1], [-1, 0], [0, -1]]
echo 'Position: x =' .. x .. ', y = ' .. y
endfor
" Iterate over a range of numbers
for i in range(10, 0, -1) " Count down from 10
echo 'T minus' .. i
endfor
" Iterate over the keys of a dictionary
for symbol in keys({'π': 3.14, 'e': 2.71})
echo 'The constant ' .. symbol .. ' is a transcendent number'
endfor
" Iterate over the values of a dictionary
for value in values({'π': 3.14, 'e': 2.71})
echo 'The value ' .. value .. ' approximates a transcendent number'
endfor
" Iterate over the keys and values of a dictionary
for [symbol, value] in items({'π': 3.14, 'e': 2.71})
echo 'The number ' .. symbol .. ' is approximately ' .. value
endfor
```
#### While-loops
```vim
while !there_yet
echo 'Are we there yet?'
endwhile
```
### Exception handling
See `:h exception-handling`
Throw new exceptions as strings, catch them by pattern-matching a regular
expression against the string
```vim
" Throw new exception
throw "Wrong arguments"
" Guard against an exception (the second catch matches any exception)
try
source path/to/file
catch /Cannot open/
echo 'Looks like that file does not exist'
catch /.*/
echo 'Something went wrong, but I don't know what'
finally
echo 'I'm done trying'
endtry
```
## Functions
### Defining functions
```vim
" Unscoped function names have to start with a capital letter
function! AddNumbersLoudly(x, y)
" Use a: scope to access arguments
echo 'Adding' .. a:x .. 'and' .. a:y |" A side effect
return a:x + a:y |" A return value
endfunction
" Scoped function names may start with a lower-case letter
function! s:addNumbersLoudly(x, y)
echo 'Adding' .. a:x .. 'and' .. a:y
return a:x + a:y
endfunction
```
Without the exclamation mark it would be an error to re-define a function, with
the exclamation mark the new definition can replace the old one. Since Vim
script files can be reloaded several times over the course of a session it is
best to use the exclamation mark unless you really know what you are doing.
Function definitions can have special qualifiers following the argument list.
```vim
" Range functions define two implicit arguments, which will be set to the range
" of the ex-command
function! FirstAndLastLine() range
echo [a:firstline, a:lastline]
endfunction
" Prints the first and last line that match a pattern (:h cmdline-ranges)
/^#!/,/!#$/call FirstAndLastLine()
" Aborting functions, abort once error occurs (:h :func-abort)
function! SourceMyFile() abort
source my-file.vim |" Try sourcing non-existing file
echo 'This will never be printed'
endfunction
" Closures, functions carrying values from outer scope (:h :func-closure)
function! MakeAdder(x)
function! Adder(n) closure
return a:n + a:x
endfunction
return funcref('Adder')
endfunction
let AddFive = MakeAdder(5)
echo AddFive(3) |" Prints 8
" Dictionary functions, poor man's OOP methods (:h Dictionary-function)
function! Mylen() dict
return len(self.data) |" Implicit variable self
endfunction
let mydict = {'data': [0, 1, 2, 3], 'len': function("Mylen")}
echo mydict.len()
" Alternatively, more concise
let mydict = {'data': [0, 1, 2, 3]}
function! mydict.len()
return len(self.data)
endfunction
```
### Calling functions
```vim
" Call a function for its return value, and possibly for its side effects
let animals = keys({'cow': 'moo', 'dog': 'woof', 'cat': 'meow'})
" Call a function for its side effects only, ignore potential result
call sign_undefine()
" The call() function calls a function reference and passes parameters as a
" list, and returns the function's result.
echo call(function('get'), [{'a': 1, 'b': 2}, 'c', 3]) |" Prints 3
```
Recall that Vim script is embedded within the ex-commands, that is why we
cannot just call a function directly, we have to use the `:call` ex-command.
### Function namespaces
See `:h write-library-script`, `:h autoload`
```vim
" Must be defined in autoload/foo/bar.vim
" Namspaced function names do not have to start with a capital letter
function! foo#bar#log(value)
echomsg value
endfunction
call foo#bar#log('Hello')
```
## Frequently used ex-commands
### Sourcing runtime files
See `:h 'runtimepath'`
```vim
" Source first match among runtime paths
runtime plugin/my-plugin.vim
```
### Defining new ex-commands
See `:h 40.2`, `:h :command`
```vim
" First argument here is the name of the command, rest is the command body
command! SwapAdjacentLines normal! ddp
```
The exclamation mark works the same as with `:function`. User-defined commands
must start with a capital letter. The `:command` command can take a number of
attributes (some of which have their own parameters with `=`), such as
`-nargs`, all of them start with a dash to set them apart from the command
name.
```vim
:command -nargs=1 Error echoerr <args>
```
### Defining auto-commands
See `:h 40.3`, `:h autocmd`, `:h autocommand-events`
```vim
" The arguments are "events", "patterns", rest is "commands"
autocmd BufWritePost $MYVIMRC source $MYVIMRC
```
Events and patterns are separated by commas with no space between. See `:h
autocmd-events` for standard events, `:h User` for custom events. Everything
else are the ex-commands which will be executed.
#### Auto groups
When a file is sourced multiple times the auto-commands are defined anew,
without deleting the old ones, causing auto-commands to pile up over time. Use
auto-groups and the following ritual to guard against this.
```vim
augroup auto-source |" The name of the group is arbitrary
autocmd! |" Deletes all auto-commands in the current group
autocmd BufWritePost $MYVIMRC source $MYVIMRC
augroup END |" Switch back to default auto-group
```
It is also possible to assign a group directly. This is useful if the
definition of the group is in one script and the definition of the auto-command
is in another script.
```vim
" In one file
augroup auto-source
autocmd!
augroup END
" In another file
autocmd auto-source BufWritePost $MYVIMRC source $MYVIMRC
```
### Executing (run-time macros of sorts)
Sometimes we need to construct an ex-command where part of the command is not
known until runtime.
```vim
let line = 3 |" Line number determined at runtime
execute line .. 'delete' |" Delete a line
```
### Executing normal-mode commands
Use `:normal` to play back a sequence of normal mode commands from the
command-line. Add an exclamation mark to ignore user mappings.
```vim
normal! ggddGp |" Transplant first line to end of buffer
" Window commands can be used with :normal, or with :wincmd if :normal would
" not work
wincmd L |" Move current window all the way to the right
```
## Frequently used functions
```vim
" Feature check
echo has('nvim') |" Running Neovim
echo has('python3') |" Support for Python 3 plugins
echo has('unix') |" Running on a Unix system
echo has('win32') |" Running on a Windows system
" Test if something exists
echo exists('&mouse') |" Option (exists only)
echo exists('+mouse') |" Option (exists and works)
echo exists('$HOSTNAME') |" Environment variable
echo exists('*strftime') |" Built-in function
echo exists('**s:MyFunc') |" User-defined function
echo exists('bufcount') |" Variable (scope optional)
echo exists('my_dict["foo"]') |" Variable (dictionary entry)
echo exists('my_dict["foo"]') |" Variable (dictionary entry)
echo exists(':Make') |" Command
echo exists("#CursorHold") |" Auto-command defined for event
echo exists("#BufReadPre#*.gz") |" Event and pattern
echo exists("#filetypeindent") |" Auto-command group
echo exists("##ColorScheme") |" Auto-commnand supported for event
" Various dynamic values (see :h expand())
echo expand('%') |" Current file name
echo expand('<cword>') |" Current word under cursor
echo expand('%:p') |" Modifier are possible
" Type tests
echo type(my_var) == type(0) |" Number
echo type(my_var) == type('') |" String
echo type(my_var) == type([]) |" List
echo type(my_var) == type({}) |" Dictionary
echo type(my_var) == type(function('type')) |" Funcref
" Format strings
echo printf('%d in hexadecimal is %X', 123, 123)
```
## Tricks of the trade
### Source guard
```vim
" Prevent a file from being source multiple times; users can set the variable
" in their configuration to prevent the plugin from loading at all.
if exists('g:loaded_my_plugin')
finish
endif
let g:loaded_my_plugin = v:true
```
### Default values
```vim
" Get a default value: if the user defines a variable use it, otherwise use a
" hard-coded default. Uses the fact that a scope is also a dictionary.
let s:greeting = get(g:, 'my_plugin_greeting', 'Hello')
```