Eval

Nvim:help pages,generated fromsource using thetree-sitter-vimdoc parser.

Expression evaluationexpressionexprE15eval

Using expressions is introduced in chapter 41 of the user manualusr_41.txt.

1. Variablesvariables

1.1 Variable types

E712E896E897E899There are seven types of variables:

NumberIntegerNumberA 32 or 64 bit signed number.expr-numberThe number of bits is available inv:numbersize.Examples: -123 0x10 0177 0o177 0b1011

FloatA floating point number.floating-point-formatFloatExamples: 123.456 1.15e-6 -1.1e3

StringA NUL terminated string of 8-bit unsigned characters (bytes).expr-string Examples: "ab\txx\"--" 'x-z''a,c'

FuncrefA reference to a functionFuncref.Example: function("strlen")It can be bound to a dictionary and arguments, it then workslike a Partial.Example: function("Callback", [arg], myDict)

ListAn ordered sequence of items, seeList for details.Example: [1, 2, ['a', 'b']]

DictionaryAn associative, unordered array: Each entry has a key and avalue.DictionaryExamples:

{"blue": "#0000ff", "red": "#ff0000"}#{blue: "#0000ff", red: "#ff0000"}

BlobBinary Large Object. Stores any sequence of bytes. SeeBlobfor details.Example: 0zFF00ED015DAF0z is an empty Blob.

The Number and String types are converted automatically, depending on how theyare used.

Conversion from a Number to a String is by making the ASCII representation ofthe Number. Examples:

Number 123-->String "123"

Number 0-->String "0"

Number -1-->String "-1"

octal
Conversion from a String to a Number is done by converting the first digits toa number. Hexadecimal "0xf9", Octal "017" or "0o17", and Binary "0b10"numbers are recognized. If the String doesn't start with digits, the resultis zero. Examples:

String "456"-->Number 456

String "6bar"-->Number 6

String "foo"-->Number 0

String "0xf1"-->Number 241

String "0100"-->Number 64

String "0o100"-->Number 64

String "0b101"-->Number 5

String "-8"-->Number -8

String "+8"-->Number 0

To force conversion from String to Number, add zero to it:

:echo "0100" + 0

To avoid a leading zero to cause octal conversion, or for using a differentbase, usestr2nr().

TRUEFALSEBooleanFor boolean operators Numbers are used. Zero is FALSE, non-zero is TRUE.You can also usev:false andv:true.When TRUE is returned from a function it is the Number one, FALSE is thenumber zero.

Note that in the command:

:if "foo":" NOT executed

"foo" is converted to 0, which means FALSE. If the string starts with anon-zero number it means TRUE:

:if "8foo":" executed

To test for a non-empty string, use empty():

:if !empty("foo")

falsytruthyAn expression can be used as a condition, ignoring the type and only usingwhether the value is "sort of true" or "sort of false". Falsy is:the number zeroempty string, blob, list or dictionaryOther values are truthy. Examples:0falsy1truthy-1truthy0.0falsy0.1truthy''falsy'x'truthy[]falsy[0]truthy{}falsy#{x: 1} truthy0zfalsy0z00truthy

non-zero-arg
Function arguments often behave slightly different fromTRUE: If theargument is present and it evaluates to a non-zero Number,v:true or anon-empty String, then the value is considered to be TRUE.Note that " " and "0" are also non-empty strings, thus considered to be TRUE.A List, Dictionary or Float is not a Number or String, thus evaluate to FALSE.

E745E728E703E729E730E731E974E975E976List,Dictionary,Funcref, andBlob types are not automaticallyconverted.

E805E806E808When mixing Number and Float the Number is converted to Float. Otherwisethere is no automatic conversion of Float. You can use str2float() for Stringto Float, printf() for Float to String and float2nr() for Float to Number.

E362E891E892E893E894E907When expecting a Float a Number can also be used, but nothing else.

no-type-checking
You will not get an error if you try to change the type of a variable.

1.2 Function references

FuncrefE695E718E1192A Funcref variable is obtained with thefunction() function, thefuncref()function or created with the lambda expressionexpr-lambda. It can be usedin an expression in the place of a function name, before the parenthesisaround the arguments, to invoke the function it refers to. Example:

:let Fn = function("MyFunc"):echo Fn()

E704E705E707A Funcref variable must start with a capital, "s:", "w:", "t:" or "b:". Youcan use "g:" but the following name must still start with a capital. Youcannot have both a Funcref variable and a function with the same name.

A special case is defining a function and directly assigning its Funcref to aDictionary entry. Example:

:function dict.init() dict:   let self.val = 0:endfunction

The key of the Dictionary can start with a lower case letter. The actualfunction name is not used here. Also seenumbered-function.

A Funcref can also be used with the:call command:

:call Fn():call dict.init()

The name of the referenced function can be obtained withstring().

:let func = string(Fn)

You can usecall() to invoke a Funcref and use a list variable for thearguments:

:let r = call(Fn, mylist)

Partial
A Funcref optionally binds a Dictionary and/or arguments. This is also calleda Partial. This is created by passing the Dictionary and/or arguments tofunction() or funcref(). When calling the function the Dictionary and/orarguments will be passed to the function. Example:

let Cb = function('Callback', ['foo'], myDict)call Cb('bar')

This will invoke the function as if using:

call myDict.Callback('foo', 'bar')

Note that binding a function to a Dictionary also happens when the function isa member of the Dictionary:

let myDict.myFunction = MyFunctioncall myDict.myFunction()

Here MyFunction() will get myDict passed as "self". This happens when the"myFunction" member is accessed. When assigning "myFunction" to otherDictand calling it, it will be bound to otherDict:

let otherDict.myFunction = myDict.myFunctioncall otherDict.myFunction()

Now "self" will be "otherDict". But when the dictionary was bound explicitlythis won't happen:

let myDict.myFunction = function(MyFunction, myDict)let otherDict.myFunction = myDict.myFunctioncall otherDict.myFunction()

Here "self" will be "myDict", because it was bound explicitly.

1.3 Lists

listListListsE686A List is an ordered sequence of items. An item can be of any type. Itemscan be accessed by their index number. Items can be added and removed at anyposition in the sequence.

List creation

E696E697A List is created with a comma-separated list of items in square brackets.Examples:

:let mylist = [1, two, 3, "four"]:let emptylist = []

An item can be any expression. Using a List for an item creates aList of Lists:

:let nestlist = [[11, 12], [21, 22], [31, 32]]

An extra comma after the last item is ignored.

List index

list-indexE684An item in the List can be accessed by putting the index in square bracketsafter the List. Indexes are zero-based, thus the first item has index zero.

:let item = mylist[0]" get the first item: 1:let item = mylist[2]" get the third item: 3

When the resulting item is a list this can be repeated:

:let item = nestlist[0][1]" get the first list, second item: 12

A negative index is counted from the end. Index -1 refers to the last item inthe List, -2 to the last but one item, etc.

:let last = mylist[-1]" get the last item: "four"

To avoid an error for an invalid index use theget() function. When an itemis not available it returns zero or the default value you specify:

:echo get(mylist, idx):echo get(mylist, idx, "NONE")

List concatenation

list-concatenation
Two lists can be concatenated with the "+" operator:

:let longlist = mylist + [5, 6]:let longlist = [5, 6] + mylist

To prepend or append an item, turn it into a list by putting [] around it.

A list can be concatenated with another one in-place using:let+= orextend():

:let mylist += [7, 8]:call extend(mylist, [7, 8])

Seelist-modification below for more about changing a list in-place.

Sublist

sublist
A part of the List can be obtained by specifying the first and last index,separated by a colon in square brackets:

:let shortlist = mylist[2:-1]" get List [3, "four"]

Omitting the first index is similar to zero. Omitting the last index issimilar to -1.

:let endlist = mylist[2:]" from item 2 to the end: [3, "four"]:let shortlist = mylist[2:2]" List with one item: [3]:let otherlist = mylist[:]" make a copy of the List

Notice that the last index is inclusive. If you prefer using an exclusiveindex use theslice() method.

If the first index is beyond the last item of the List or the second item isbefore the first item, the result is an empty list. There is no errormessage.

If the second index is equal to or greater than the length of the list thelength minus one is used:

:let mylist = [0, 1, 2, 3]:echo mylist[2:8]" result: [2, 3]

NOTE: mylist[s:e] means using the variable "s:e" as index. Watch out forusing a single letter variable before the ":". Insert a space when needed:mylist[s : e].

List identity

list-identity
When variable "aa" is a list and you assign it to another variable "bb", bothvariables refer to the same list. Thus changing the list "aa" will alsochange "bb":

:let aa = [1, 2, 3]:let bb = aa:call add(aa, 4):echo bb

[1, 2, 3, 4]

Making a copy of a list is done with thecopy() function. Using [:] alsoworks, as explained above. This creates a shallow copy of the list: Changinga list item in the list will also change the item in the copied list:

:let aa = [[1, 'a'], 2, 3]:let bb = copy(aa):call add(aa, 4):let aa[0][1] = 'aaa':echo aa

[[1, aaa], 2, 3, 4]

:echo bb

[[1, aaa], 2, 3]

To make a completely independent list usedeepcopy(). This also makes acopy of the values in the list, recursively. Up to a hundred levels deep.

The operator "is" can be used to check if two variables refer to the sameList. "isnot" does the opposite. In contrast "==" compares if two lists havethe same value.

:let alist = [1, 2, 3]:let blist = [1, 2, 3]:echo alist is blist

:echo alist == blist

Note about comparing lists: Two lists are considered equal if they have thesame length and all items compare equal, as with using "==". There is oneexception: When comparing a number with a string they are considereddifferent. There is no automatic type conversion, as with using "==" onvariables. Example:

echo 4 == "4"

echo [4] == ["4"]

Thus comparing Lists is more strict than comparing numbers and strings. Youcan compare simple values this way too by putting them in a list:

:let a = 5:let b = "5":echo a == b

:echo [a] == [b]

List unpack

To unpack the items in a list to individual variables, put the variables insquare brackets, like list items:

:let [var1, var2] = mylist

When the number of variables does not match the number of items in the listthis produces an error. To handle any extra items from the list append ";"and a variable name:

:let [var1, var2; rest] = mylist

This works like:

:let var1 = mylist[0]:let var2 = mylist[1]:let rest = mylist[2:]

Except that there is no error if there are only two items. "rest" will be anempty list then.

List modification

list-modification
To change a specific item of a list use:let this way:

:let list[4] = "four":let listlist[0][3] = item

To change part of a list you can specify the first and last item to bemodified. The value must at least have the number of items in the range:

:let list[3:5] = [3, 4, 5]

To add items to a List in-place, you can use:let+= (list-concatenation):

:let listA = [1, 2]:let listA += [3, 4]

When two variables refer to the same List, changing one List in-place willcause the referenced List to be changed in-place:

:let listA = [1, 2]:let listB = listA:let listB += [3, 4]:echo listA[1, 2, 3, 4]

Adding and removing items from a list is done with functions. Here are a fewexamples:

:call insert(list, 'a')" prepend item 'a':call insert(list, 'a', 3)" insert item 'a' before list[3]:call add(list, "new")" append String item:call add(list, [1, 2])" append a List as one new item:call extend(list, [1, 2])" extend the list with two more items:let i = remove(list, 3)" remove item 3:unlet list[3]" idem:let l = remove(list, 3, -1)" remove items 3 to last item:unlet list[3 : ]" idem:call filter(list, 'v:val !~ "x"')  " remove items with an 'x'

Changing the order of items in a list:

:call sort(list)" sort a list alphabetically:call reverse(list)" reverse the order of items:call uniq(sort(list))" sort and remove duplicates

For loop

The:for loop executes commands for each item in aList,String orBlob.A variable is set to each item in sequence. Example with a List:

:for item in mylist:   call Doit(item):endfor

This works like:

:let index = 0:while index < len(mylist):   let item = mylist[index]:   :call Doit(item):   let index = index + 1:endwhile

If all you want to do is modify each item in the list then themap()function will be a simpler method than a for loop.

Just like the:let command,:for also accepts a list of variables. Thisrequires the argument to be a List of Lists.

:for [lnum, col] in [[1, 3], [2, 8], [3, 0]]:   call Doit(lnum, col):endfor

This works like a:let command is done for each list item. Again, the typesmust remain the same to avoid an error.

It is also possible to put remaining items in a List variable:

:for [i, j; rest] in listlist:   call Doit(i, j):   if !empty(rest):      echo "remainder: " .. string(rest):   endif:endfor

For a Blob one byte at a time is used.

For a String one character, including any composing characters, is used as aString. Example:

for c in text  echo 'This character is ' .. cendfor

List functions

E714
Functions that are useful with a List:

:let r = call(funcname, list)" call a function with an argument list:if empty(list)" check if list is empty:let l = len(list)" number of items in list:let big = max(list)" maximum value in list:let small = min(list)" minimum value in list:let xs = count(list, 'x')" count nr of times 'x' appears in list:let i = index(list, 'x')" index of first 'x' in list:let lines = getline(1, 10)" get ten text lines from buffer:call append('$', lines)" append text lines in buffer:let list = split("a b c")" create list from items in a string:let string = join(list, ', ')" create string from list items:let s = string(list)" String representation of list:call map(list, '">> " .. v:val')  " prepend ">> " to each item

Don't forget that a combination of features can make things simple. Forexample, to add up all the numbers in a list:

:exe 'let sum = ' .. join(nrlist, '+')

1.4 Dictionaries

DictdictDictionariesDictionaryA Dictionary is an associative array: Each entry has a key and a value. Theentry can be located with the key. The entries are stored without a specificordering.

Dictionary creation

E720E721E722E723A Dictionary is created with a comma-separated list of entries in curlybraces. Each entry has a key and a value, separated by a colon. Each key canonly appear once. Examples:

:let mydict = {1: 'one', 2: 'two', 3: 'three'}:let emptydict = {}

E713E716E717A key is always a String. You can use a Number, it will be converted to aString automatically. Thus the String '4' and the number 4 will find the sameentry. Note that the String '04' and the Number 04 are different, since theNumber will be converted to the String '4', leading zeros are dropped. Theempty string can also be used as a key.literal-Dict#{}To avoid having to put quotes around every key the #{} form can be used. Thisdoes require the key to consist only of ASCII letters, digits, '-' and '_'.Example:

:let mydict = #{zero: 0, one_key: 1, two-key: 2, 333: 3}

Note that 333 here is the string "333". Empty keys are not possible with #{}.

A value can be any expression. Using a Dictionary for a value creates anested Dictionary:

:let nestdict = {1: {11: 'a', 12: 'b'}, 2: {21: 'c'}}

An extra comma after the last entry is ignored.

Accessing entries

The normal way to access an entry is by putting the key in square brackets:

:let val = mydict["one"]:let mydict["four"] = 4

You can add new entries to an existing Dictionary this way, unlike Lists.

For keys that consist entirely of letters, digits and underscore the followingform can be usedexpr-entry:

:let val = mydict.one:let mydict.four = 4

Since an entry can be any type, also a List and a Dictionary, the indexing andkey lookup can be repeated:

:echo dict.key[idx].key

Dictionary to List conversion

You may want to loop over the entries in a dictionary. For this you need toturn the Dictionary into a List and pass it to:for.

Most often you want to loop over the keys, using thekeys() function:

:for key in keys(mydict):   echo key .. ': ' .. mydict[key]:endfor

The List of keys is unsorted. You may want to sort them first:

:for key in sort(keys(mydict))

To loop over the values use thevalues() function:

:for v in values(mydict):   echo "value: " .. v:endfor

If you want both the key and the value use theitems() function. It returnsa List in which each item is a List with two items, the key and the value:

:for [key, value] in items(mydict):   echo key .. ': ' .. value:endfor

Dictionary identity

dict-identity
Just like Lists you need to usecopy() anddeepcopy() to make a copy of aDictionary. Otherwise, assignment results in referring to the sameDictionary:

:let onedict = {'a': 1, 'b': 2}:let adict = onedict:let adict['a'] = 11:echo onedict['a']11

Two Dictionaries compare equal if all the key-value pairs compare equal. Formore info seelist-identity.

Dictionary modification

dict-modification
To change an already existing entry of a Dictionary, or to add a new entry,use:let this way:

:let dict[4] = "four":let dict['one'] = item

Removing an entry from a Dictionary is done withremove() or:unlet.Three ways to remove the entry with key "aaa" from dict:

:let i = remove(dict, 'aaa'):unlet dict.aaa:unlet dict['aaa']

Merging a Dictionary with another is done withextend():

:call extend(adict, bdict)

This extends adict with all entries from bdict. Duplicate keys cause entriesin adict to be overwritten. An optional third argument can change this.Note that the order of entries in a Dictionary is irrelevant, thus don'texpect ":echo adict" to show the items from bdict after the older entries inadict.

Weeding out entries from a Dictionary can be done withfilter():

:call filter(dict, 'v:val =~ "x"')

This removes all entries from "dict" with a value not matching 'x'.This can also be used to remove all entries:

call filter(dict, 0)

Dictionary function

Dictionary-functionselfE725E862When a function is defined with the "dict" attribute it can be used in aspecial way with a dictionary. Example:

:function Mylen() dict:   return len(self.data):endfunction:let mydict = {'data': [0, 1, 2, 3], 'len': function("Mylen")}:echo mydict.len()

This is like a method in object oriented programming. The entry in theDictionary is aFuncref. The local variable "self" refers to the dictionarythe function was invoked from.

It is also possible to add a function without the "dict" attribute as aFuncref to a Dictionary, but the "self" variable is not available then.

numbered-functionanonymous-functionTo avoid the extra name for the function it can be defined and directlyassigned to a Dictionary in this way:

:let mydict = {'data': [0, 1, 2, 3]}:function mydict.len():   return len(self.data):endfunction:echo mydict.len()

The function will then get a number and the value of dict.len is aFuncrefthat references this function. The function can only be used through aFuncref. It will automatically be deleted when there is noFuncrefremaining that refers to it.

It is not necessary to use the "dict" attribute for a numbered function.

If you get an error for a numbered function, you can find out what it is witha trick. Assuming the function is 42, the command is:

:function g:42

Functions for Dictionaries

E715
Functions that can be used with a Dictionary:

:if has_key(dict, 'foo')" TRUE if dict has entry with key "foo":if empty(dict)" TRUE if dict is empty:let l = len(dict)" number of items in dict:let big = max(dict)" maximum value in dict:let small = min(dict)" minimum value in dict:let xs = count(dict, 'x')" count nr of times 'x' appears in dict:let s = string(dict)" String representation of dict:call map(dict, '">> " .. v:val')  " prepend ">> " to each item

1.5 Blobs

blobBlobBlobsE978A Blob is a binary object. It can be used to read an image from a file andsend it over a channel, for example.

A Blob mostly behaves like aList of numbers, where each number has thevalue of an 8-bit byte, from 0 to 255.

Blob creation

A Blob can be created with ablob-literal:

:let b = 0zFF00ED015DAF

Dots can be inserted between bytes (pair of hex characters) for readability,they don't change the value:

:let b = 0zFF00.ED01.5DAF

A blob can be read from a file withreadfile() passing the{type} argumentset to "B", for example:

:let b = readfile('image.png', 'B')

Blob index

blob-indexE979A byte in the Blob can be accessed by putting the index in square bracketsafter the Blob. Indexes are zero-based, thus the first byte has index zero.

:let myblob = 0z00112233:let byte = myblob[0]" get the first byte: 0x00:let byte = myblob[2]" get the third byte: 0x22

A negative index is counted from the end. Index -1 refers to the last byte inthe Blob, -2 to the last but one byte, etc.

:let last = myblob[-1]" get the last byte: 0x33

To avoid an error for an invalid index use theget() function. When an itemis not available it returns -1 or the default value you specify:

:echo get(myblob, idx):echo get(myblob, idx, 999)

Blob iteration

The:for loop executes commands for each byte of a Blob. The loop variable isset to each byte in the Blob. Example:

:for byte in 0z112233:   call Doit(byte):endfor

This calls Doit() with 0x11, 0x22 and 0x33.

Blob concatenation

blob-concatenation
Two blobs can be concatenated with the "+" operator:

:let longblob = myblob + 0z4455:let longblob = 0z4455 + myblob

A blob can be concatenated with another one in-place using:let+=:

:let myblob += 0z6677

Seeblob-modification below for more about changing a blob in-place.

Part of a blob

A part of the Blob can be obtained by specifying the first and last index,separated by a colon in square brackets:

:let myblob = 0z00112233:let shortblob = myblob[1:2]" get 0z1122:let shortblob = myblob[2:-1]" get 0z2233

Omitting the first index is similar to zero. Omitting the last index issimilar to -1.

:let endblob = myblob[2:]" from item 2 to the end: 0z2233:let shortblob = myblob[2:2]" Blob with one byte: 0z22:let otherblob = myblob[:]" make a copy of the Blob

If the first index is beyond the last byte of the Blob or the second index isbefore the first index, the result is an empty Blob. There is no errormessage.

If the second index is equal to or greater than the length of the Blob thelength minus one is used:

:echo myblob[2:8]" result: 0z2233

Blob modification

blob-modification
To change a specific byte of a blob use:let this way:

:let blob[4] = 0x44

When the index is just one beyond the end of the Blob, it is appended. Anyhigher index is an error.

To change a sequence of bytes the [:] notation can be used:

let blob[1:3] = 0z445566

The length of the replaced bytes must be exactly the same as the valueprovided.E972

To change part of a blob you can specify the first and last byte to bemodified. The value must have the same number of bytes in the range:

:let blob[3:5] = 0z334455

To add items to a Blob in-place, you can use:let+= (blob-concatenation):

:let blobA = 0z1122:let blobA += 0z3344

When two variables refer to the same Blob, changing one Blob in-place willcause the referenced Blob to be changed in-place:

:let blobA = 0z1122:let blobB = blobA:let blobB += 0z3344:echo blobA0z11223344

You can also use the functionsadd(),remove() andinsert().

Blob identity

Blobs can be compared for equality:

if blob == 0z001122

And for equal identity:

if blob is otherblob

blob-identityE977When variable "aa" is a Blob and you assign it to another variable "bb", bothvariables refer to the same Blob. Then the "is" operator returns true.

When making a copy using [:] orcopy() the values are the same, but theidentity is different:

:let blob = 0z112233:let blob2 = blob:echo blob == blob2

:echo blob is blob2

:let blob3 = blob[:]:echo blob == blob3

:echo blob is blob3

Making a copy of a Blob is done with thecopy() function. Using [:] alsoworks, as explained above.

1.6 More about variables

more-variables
If you need to know the type of a variable or expression, use thetype()function.

When the '!' flag is included in the'shada' option, global variables thatstart with an uppercase letter, and don't contain a lowercase letter, arestored in the shada fileshada-file.

When the'sessionoptions' option contains "global", global variables thatstart with an uppercase letter and contain at least one lowercase letter arestored in the session filesession-file.

variable namecan be stored where

my_var_6notMy_Var_6session fileMY_VAR_6shada file

It's possible to form a variable name with curly braces, seecurly-braces-names.

2. Expression syntaxexpression-syntax

Expression syntax summary, from least to most significant:

expr1 expr2expr2 ? expr1 : expr1if-then-else

expr2 expr3expr3 || expr3 ...logical OR

expr3 expr4expr4 && expr4 ...logical AND

expr4 expr5expr5 == expr5equalexpr5 != expr5not equalexpr5 > expr5greater thanexpr5 >= expr5greater than or equalexpr5 < expr5smaller thanexpr5 <= expr5smaller than or equalexpr5 =~ expr5regexp matchesexpr5 !~ expr5regexp doesn't match

expr5 ==? expr5equal, ignoring caseexpr5 ==# expr5equal, match caseetc.As above, append ? for ignoring case, # formatching case

expr5 is expr5sameList,Dictionary orBlob instanceexpr5 isnot expr5differentList,Dictionary orBlobinstance

expr5 expr6expr6 + expr6 ...number addition, list or blob concatenationexpr6 - expr6 ...number subtractionexpr6 . expr6 ...string concatenationexpr6 .. expr6 ...string concatenation

expr6 expr7expr7 * expr7 ...number multiplicationexpr7 / expr7 ...number divisionexpr7 % expr7 ...number modulo

expr7 expr8! expr7logical NOT

expr7unary minus+ expr7unary plus

expr8 expr9expr8[expr1]byte of a String or item of aListexpr8[expr1 : expr1]substring of a String or sublist of aListexpr8.nameentry in aDictionaryexpr8(expr1, ...)function call withFuncref variableexpr8->name(expr1, ...)method call

expr9 numbernumber constant"string"string constant, backslash is special'string' string constant, ' is doubled[expr1, ...]List{expr1: expr1, ...}Dictionary #{key: expr1, ...}Dictionary &optionoption value(expr1)nested expressionvariableinternal variableva{ria}bleinternal variable with curly braces$VARenvironment variable@rcontents of register "r"function(expr1, ...)function callfunc{ti}on(expr1, ...)function call with curly braces{args -> expr1} lambda expression

"..." indicates that the operations in this level can be concatenated.Example:

&nu || &list && &shell == "csh"

All expressions within one level are parsed from left to right.

Expression nesting is limited to 1000 levels deep (300 when build with MSVC)to avoid running out of stack and crashing.E1169

expr1expr1ternaryfalsy-operator??E109

The ternary operator: expr2 ? expr1 : expr1The falsy operator: expr2 ?? expr1

Ternary operator

The expression before the '?' is evaluated to a number. If it evaluates toTRUE, the result is the value of the expression between the '?' and ':',otherwise the result is the value of the expression after the ':'.Example:

:echo lnum == 1 ? "top" : lnum

Since the first expression is an "expr2", it cannot contain another ?:. Theother two expressions can, thus allow for recursive use of ?:.Example:

:echo lnum == 1 ? "top" : lnum == 1000 ? "last" : lnum

To keep this readable, usingline-continuation is suggested:

:echo lnum == 1:\? "top":\: lnum == 1000:\? "last":\: lnum

You should always put a space before the ':', otherwise it can be mistaken foruse in a variable such as "a:1".

Falsy operator

This is also known as the "null coalescing operator", but that's toocomplicated, thus we just call it the falsy operator.

The expression before the '??' is evaluated. If it evaluates totruthy, this is used as the result. Otherwise the expression after the '??'is evaluated and used as the result. This is most useful to have a defaultvalue for an expression that may result in zero or empty:

echo theList ?? 'list is empty'echo GetName() ?? 'unknown'

These are similar, but not equal:

expr2 ?? expr1expr2 ? expr2 : expr1

In the second line "expr2" is evaluated twice.

expr2 and expr3expr2expr3

expr3 || expr3 ..logical ORexpr-barbar
expr4 && expr4 ..logical ANDexpr-&&

The "||" and "&&" operators take one argument on each side. The argumentsare (converted to) Numbers. The result is:

input output

n1n2n1 || n2n1 && n2

FALSE FALSE FALSE FALSE FALSE TRUE TRUE FALSE TRUE FALSE TRUE FALSE TRUE TRUE TRUE TRUE

The operators can be concatenated, for example:

&nu || &list && &shell == "csh"

Note that "&&" takes precedence over "||", so this has the meaning of:

&nu || (&list && &shell == "csh")

Once the result is known, the expression "short-circuits", that is, furtherarguments are not evaluated. This is like what happens in C. For example:

let a = 1echo a || b

This is valid even if there is no variable called "b" because "a" isTRUE,so the result must beTRUE. Similarly below:

echo exists("b") && b == "yes"

This is valid whether "b" has been defined or not. The second clause willonly be evaluated if "b" has been defined.

expr4expr4

expr5{cmp} expr5

Compare two expr5 expressions, resulting in a 0 if it evaluates to false, or 1if it evaluates to true.

expr-==expr-!=expr->expr->=
expr-<expr-<=expr-=~expr-!~expr-==#expr-!=#expr->#expr->=#expr-<#expr-<=#expr-=~#expr-!~#expr-==?expr-!=?expr->?expr->=?expr-<?expr-<=?expr-=~?expr-!~?expr-isexpr-isnotexpr-is#expr-isnot#expr-is?expr-isnot?

use'ignorecase' match case ignore case

equal====#==?not equal!=!=#!=?greater than>>#>?greater than or equal>=>=#>=?smaller than<<#<?smaller than or equal<=<=#<=?regexp matches=~=~#=~?regexp doesn't match!~!~#!~?same instanceisis#is?different instanceisnotisnot#isnot?

Examples:"abc" ==# "Abc" evaluates to 0"abc" ==? "Abc" evaluates to 1"abc" == "Abc" evaluates to 1 if'ignorecase' is set, 0 otherwise

E691E692AList can only be compared with aList and only "equal", "not equal","is" and "isnot" can be used. This compares the values of the list,recursively. Ignoring case means case is ignored when comparing item values.

E735E736ADictionary can only be compared with aDictionary and only "equal", "notequal", "is" and "isnot" can be used. This compares the key/values of theDictionary recursively. Ignoring case means case is ignored when comparingitem values.

E694
AFuncref can only be compared with aFuncref and only "equal", "notequal", "is" and "isnot" can be used. Case is never ignored. Whetherarguments or a Dictionary are bound (with a partial) matters. TheDictionaries must also be equal (or the same, in case of "is") and thearguments must be equal (or the same).

To compare Funcrefs to see if they refer to the same function, ignoring boundDictionary and arguments, useget() to get the function name:

if get(Part1, 'name') == get(Part2, 'name')   " Part1 and Part2 refer to the same function

Using "is" or "isnot" with aList,Dictionary orBlob checks whetherthe expressions are referring to the sameList,Dictionary orBlobinstance. A copy of aList is different from the originalList. Whenusing "is" without aList,Dictionary orBlob, it is equivalent tousing "equal", using "isnot" is equivalent to using "not equal". Except thata different type means the values are different:

echo 4 == '4'1echo 4 is '4'0echo 0 is []0

"is#"/"isnot#" and "is?"/"isnot?" can be used to match and ignore case.

When comparing a String with a Number, the String is converted to a Number,and the comparison is done on Numbers. This means that:

echo 0 == 'x'1

because 'x' converted to a Number is zero. However:

echo [0] == ['x']0

Inside a List or Dictionary this conversion is not used.

When comparing two Strings, this is done with strcmp() or stricmp(). Thisresults in the mathematical difference (comparing byte values), notnecessarily the alphabetical difference in the local language.

When using the operators with a trailing '#', or the short version and'ignorecase' is off, the comparing is done with strcmp(): case matters.

When using the operators with a trailing '?', or the short version and'ignorecase' is set, the comparing is done with stricmp(): case is ignored.

'smartcase' is not used.

The "=~" and "!~" operators match the lefthand argument with the righthandargument, which is used as a pattern. Seepattern for what a pattern is.This matching is always done like'magic' was set and'cpoptions' is empty, nomatter what the actual value of'magic' or'cpoptions' is. This makes scriptsportable. To avoid backslashes in the regexp pattern to be doubled, use asingle-quote string, seeliteral-string.Since a string is considered to be a single line, a multi-line pattern(containing \n, backslash-n) will not match. However, a literal NL charactercan be matched like an ordinary character. Examples:"foo\nbar" =~ "\n"evaluates to 1"foo\nbar" =~ "\\n"evaluates to 0

expr5 and expr6expr5expr6

expr6 + expr6 Number addition,List orBlob concatenationexpr-+ expr6 - expr6 Number subtractionexpr--
expr6 . expr6 String concatenationexpr-.
expr6 .. expr6 String concatenationexpr-..

ForLists only "+" is possible and then both expr6 must be a list. Theresult is a new list with the two lists Concatenated.

For String concatenation ".." is preferred, since "." is ambiguous, it is alsoused forDict member access and floating point numbers.

expr7 * expr7 Number multiplicationexpr-star
expr7 / expr7 Number divisionexpr-/
expr7 % expr7 Number moduloexpr-%

For all, except "." and "..", Strings are converted to Numbers.For bitwise operators seeand(),or() andxor().

Note the difference between "+" and ".":"123" + "456" = 579"123" . "456" = "123456"

Since '.' has the same precedence as '+' and '-', you need to read:

1 . 90 + 90.0

As:

(1 . 90) + 90.0

That works, since the String "190" is automatically converted to the Number190, which can be added to the Float 90.0. However:

1 . 90 * 90.0

Should be read as:

1 . (90 * 90.0)

Since '.' has lower precedence than "*". This does NOT work, since thisattempts to concatenate a Float and a String.

When dividing a Number by zero the result depends on the value: 0 / 0 = -0x80000000(like NaN for Float) >0 / 0 = 0x7fffffff(like positive infinity) <0 / 0 = -0x7fffffff(like negative infinity)(before Vim 7.2 it was always 0x7fffffff)

When 64-bit Number support is enabled: 0 / 0 = -0x8000000000000000(like NaN for Float) >0 / 0 = 0x7fffffffffffffff(like positive infinity) <0 / 0 = -0x7fffffffffffffff(like negative infinity)

When the righthand side of '%' is zero, the result is 0.

None of these work forFuncrefs.

. and % do not work for Float.E804

expr7expr7

! expr7logical NOTexpr-!

expr7unary minusexpr-unary--
+ expr7unary plusexpr-unary-+

For '!'TRUE becomesFALSE,FALSE becomesTRUE (one).For '-' the sign of the number is changed.For '+' the number is unchanged. Note: "++" has no effect.

A String will be converted to a Number first.

These three can be repeated and mixed. Examples:!-1 == 0!!8 == 1--9 == 9

expr8expr8

This expression is eitherexpr9 or a sequence of the alternatives below,in any order. E.g., these are all possible:expr8[expr1].nameexpr8.name[expr1]expr8(expr1, ...)[expr1].nameexpr8->(expr1, ...)[expr1]Evaluation is always from left to right.

expr8[expr1]item of String orListexpr-[]E111subscript
In legacy Vim script:If expr8 is a Number or String this results in a String that contains theexpr1'th single byte from expr8. expr8 is used as a String (a number isautomatically converted to a String), expr1 as a Number. This doesn'trecognize multibyte encodings, seebyteidx() for an alternative, or usesplit() to turn the string into a list of characters. Example, to get thebyte under the cursor:

:let c = getline(".")[col(".") - 1]

Index zero gives the first byte. This is like it works in C. Careful:text column numbers start with one! Example, to get the byte under thecursor:

:let c = getline(".")[col(".") - 1]

Index zero gives the first byte. Careful: text column numbers start with one!

If the length of the String is less than the index, the result is an emptyString. A negative index always results in an empty string (reason: backwardcompatibility). Use [-1:] to get the last byte.

If expr8 is aList then it results the item at index expr1. Seelist-indexfor possible index values. If the index is out of range this results in anerror. Example:

:let item = mylist[-1]" get last item

Generally, if aList index is equal to or higher than the length of theList, or more negative than the length of theList, this results in anerror.

expr8[expr1a : expr1b]substring orsublistexpr-[:]substring

If expr8 is a String this results in the substring with the bytes orcharacters from expr1a to and including expr1b. expr8 is used as a String,expr1a and expr1b are used as a Number.

In legacy Vim script the indexes are byte indexes. This doesn't recognizemultibyte encodings, seebyteidx() for computing the indexes. If expr8 isa Number it is first converted to a String.

The item at index expr1b is included, it is inclusive. For an exclusive indexuse theslice() function.

If expr1a is omitted zero is used. If expr1b is omitted the length of thestring minus one is used.

A negative number can be used to measure from the end of the string. -1 isthe last character, -2 the last but one, etc.

If an index goes out of range for the string characters are omitted. Ifexpr1b is smaller than expr1a the result is an empty string.

Examples:

:let c = name[-1:]" last byte of a string:let c = name[0:-1]" the whole string:let c = name[-2:-2]" last but one byte of a string:let s = line(".")[4:]" from the fifth byte to the end:let s = s[:-3]" remove last two bytes

slice
If expr8 is aList this results in a newList with the items indicated bythe indexes expr1a and expr1b. This works like with a String, as explainedjust above. Also seesublist below. Examples:

:let l = mylist[:3]" first four items:let l = mylist[4:4]" List with one item:let l = mylist[:]" shallow copy of a List

If expr8 is aBlob this results in a newBlob with the bytes in theindexes expr1a and expr1b, inclusive. Examples:

:let b = 0zDEADBEEF:let bs = b[1:2]" 0zADBE:let bs = b[]" copy of 0zDEADBEEF

Using expr8[expr1] or expr8[expr1a : expr1b] on aFuncref results in anerror.

Watch out for confusion between a namespace and a variable followed by a colonfor a sublist:

mylist[n:]     " uses variable nmylist[s:]     " uses namespace s:, error!

expr8.nameentry in aDictionaryexpr-entry

If expr8 is aDictionary and it is followed by a dot, then the followingname will be used as a key in theDictionary. This is just like:expr8[name].

The name must consist of alphanumeric characters, just like a variable name,but it may start with a number. Curly braces cannot be used.

There must not be white space before or after the dot.

Examples:

:let dict = {"one": 1, 2: "two"}:echo dict.one" shows "1":echo dict.2" shows "two":echo dict .2" error because of space before the dot

Note that the dot is also used for String concatenation. To avoid confusionalways put spaces around the dot for String concatenation.

expr8(expr1, ...)Funcref function callE1085

When expr8 is aFuncref type variable, invoke the function it refers to.

expr8->name([args])method callmethod->expr8->{lambda}([args])

E260E276For methods that are also available as global functions this is the same as:

name(expr8 [, args])

There can also be methods specifically for the type of "expr8".

This allows for chaining, passing the value that one method returns to thenext method:

mylist->filter(filterexpr)->map(mapexpr)->sort()->join()

Example of using a lambda:

GetPercentage()->{x -> x * 100}()->printf('%d%%')

When using -> theexpr7 operators will be applied first, thus:

-1.234->string()

Is equivalent to:

(-1.234)->string()

And NOT:

-(1.234->string())

E274
"->name(" must not contain white space. There can be white space before the"->" and after the "(", thus you can split the lines like this:

mylist\ ->filter(filterexpr)\ ->map(mapexpr)\ ->sort()\ ->join()

When using the lambda form there must be no white space between the } and the

(.

expr9

number

numbernumber constantexpr-number

0xhex-number0ooctal-numberbinary-numberDecimal, Hexadecimal (starting with 0x or 0X), Binary (starting with 0b or 0B)and Octal (starting with 0, 0o or 0O).

floating-point-format
Floating point numbers can be written in two forms:

[-+]{N}.{M}[-+]{N}.{M}[eE][-+]{exp}

{N} and{M} are numbers. Both{N} and{M} must be present and can onlycontain digits.[-+] means there is an optional plus or minus sign.{exp} is the exponent, power of 10.Only a decimal point is accepted, not a comma. No matter what the currentlocale is.

Examples:123.456+0.000155.0-0.1231.234e031.0E-6-3.1416e+88

These are INVALID:3.empty{M}1e40missing .{M}

Rationale:Before floating point was introduced, the text "123.456" was interpreted asthe two numbers "123" and "456", both converted to a string and concatenated,resulting in the string "123456". Since this was considered pointless, and wecould not find it intentionally being used in Vim scripts, this backwardsincompatibility was accepted in favor of being able to use the normal notationfor floating point numbers.

float-pifloat-eA few useful values to copy&paste:

:let pi = 3.14159265359:let e  = 2.71828182846

Or, if you don't want to write them in as floating-point literals, you canalso use functions, like the following:

:let pi = acos(-1.0):let e  = exp(1.0)

floating-point-precision
The precision and range of floating points numbers depends on what "double"means in the library Vim was compiled with. There is no way to change this atruntime.

The default for displaying aFloat is to use 6 decimal places, like usingprintf("%g", f). You can select something else when using theprintf()function. Example:

:echo printf('%.15e', atan(1))

7.853981633974483e-01

stringstringStringexpr-stringE114

"string"string constantexpr-quote

Note that double quotes are used.

A string constant accepts these special characters:\...three-digit octal number (e.g., "\316")\..two-digit octal number (must be followed by non-digit)\.one-digit octal number (must be followed by non-digit)\x..byte specified with two hex numbers (e.g., "\x1f")\x.byte specified with one hex number (must be followed by non-hex char)\X..same as \x..\X.same as \x.\u....character specified with up to 4 hex numbers, stored as UTF-8(e.g., "\u02a4")\U....same as \u but allows up to 8 hex numbers.\bbackspace<BS>\eescape<Esc>\fformfeed 0x0C\nnewline<NL>\rreturn<CR>\ttab<Tab>\\backslash\"double quote\<xxx>Special key named "xxx". e.g. "\<C-W>" forCTRL-W. This is for usein mappings, the 0x80 byte is escaped.To use the double quote character it must be escaped: "<M-\">".Don't use<Char-xxxx> to get a UTF-8 character, use \uxxxx asmentioned above.\<*xxx>Like \<xxx> but prepends a modifier instead of including it in thecharacter. E.g. "\<C-w>" is one character 0x17 while "\<*C-w>" is fourbytes: 3 for the CTRL modifier and then character "W".

Note that "\xff" is stored as the byte 255, which may be invalid in someencodings. Use "\u00ff" to store character 255 correctly as UTF-8.

Note that "\000" and "\x00" force the end of the string.

blob-literalblob-literalE973

Hexadecimal starting with 0z or 0Z, with an arbitrary number of bytes.The sequence must be an even number of hex characters. Example:

:let b = 0zFF00ED015DAF

literal-stringliteral-stringE115

stringstring constantexpr-'

Note that single quotes are used.

This string is taken as it is. No backslashes are removed or have a specialmeaning. The only exception is that two quotes stand for one quote.

Single quoted strings are useful for patterns, so that backslashes do not needto be doubled. These two commands are equivalent:

if a =~ "\\s*"if a =~ '\s*'

interpolated-string$quoteinterpolated-string

$"string"interpolated string constantexpr-$quote
$'string'interpolated literal string constantexpr-$'

Interpolated strings are an extension of thestring andliteral-string,allowing the inclusion of Vim script expressions (seeexpr1). Anyexpression returning a value can be enclosed between curly braces. The valueis converted to a string. All the text and results of the expressionsare concatenated to make a new string.E1278
To include an opening brace '{' or closing brace '}' in the string contentdouble it. For double quoted strings using a backslash also works. A singleclosing brace '}' will result in an error.

Examples:

let your_name = input("What's your name? ")

What's your name? Peter

echoecho $"Hello, {your_name}!"

Hello, Peter!

echo $"The square root of {{9}} is {sqrt(9)}"

The square root of{9} is 3.0

string-offset-encoding
A string consists of multiple characters. UTF-8 uses one byte for ASCIIcharacters, two bytes for other latin characters and more bytes for othercharacters.

A string offset can count characters or bytes. Other programs may useUTF-16 encoding (16-bit words) and an offset of UTF-16 words. Some functionsuse byte offsets, usually for UTF-8 encoding. Other functions use characteroffsets, in which case the encoding doesn't matter.

The different offsets for the string "a©😊" are below:

UTF-8 offsets: [0]: 61, [1]: C2, [2]: A9, [3]: F0, [4]: 9F, [5]: 98, [6]: 8A UTF-16 offsets: [0]: 0061, [1]: 00A9, [2]: D83D, [3]: DE0A UTF-32 (character) offsets: [0]: 00000061, [1]: 000000A9, [2]: 0001F60A

You can use the "g8" and "ga" commands on a character to see thedecimal/hex/octal values.

The functionsbyteidx(),utf16idx() andcharidx() can be used to convertbetween these indices. The functionsstrlen(),strutf16len() andstrcharlen() return the number of bytes, UTF-16 code units and characters ina string respectively.

optionexpr-optionE112E113

&optionoption value, local value if possible&g:optionglobal option value&l:optionlocal option value

Examples:

echo "tabstop is " .. &tabstopif &expandtab

Any option name can be used here. Seeoptions. When using the local valueand there is no buffer-local or window-local value, the global value is usedanyway.

registerexpr-register@r

@rcontents of register 'r'

The result is the contents of the named register, as a single string.Newlines are inserted where required. To get the contents of the unnamedregister use @" or @@. Seeregisters for an explanation of the availableregisters.

When using the '=' register you get the expression itself, not what itevaluates to. Useeval() to evaluate it.

nestingexpr-nestingE110-------(expr1)nested expression

environment variableexpr-env

$VARenvironment variable

The String value of any environment variable. When it is not defined, theresult is an empty string.

The functionsgetenv() andsetenv() can also be used and work forenvironment variables with non-alphanumeric names.The functionenviron() can be used to get a Dict with all environmentvariables.

expr-env-expand
Note that there is a difference between using $VAR directly and usingexpand("$VAR"). Using it directly will only expand environment variables thatare known inside the current Vim session. Using expand() will first try usingthe environment variables known inside the current Vim session. If thatfails, a shell will be used to expand the variable. This can be slow, but itdoes expand all variables that the shell knows about. Example:

:echo $shell:echo expand("$shell")

The first one probably doesn't echo anything, the second echoes the $shellvariable (if your shell supports it).

internal variableexpr-variable

variableinternal variableSee belowinternal-variables.

function callexpr-functionE116E118E119E120

function(expr1, ...)function callSee belowfunctions.

lambda expressionexpr-lambdalambda

{args -> expr1} lambda expressionE451

A lambda expression creates a new unnamed function which returns the result ofevaluatingexpr1. Lambda expressions differ fromuser-functions inthe following ways:

1. The body of the lambda expression is anexpr1 and not a sequence ofEx commands.2. The prefix "a:" should not be used for arguments. E.g.:

:let F = {arg1, arg2 -> arg1 - arg2}:echo F(5, 2)

The arguments are optional. Example:

:let F = {-> 'error function'}:echo F('ignored')

error functionclosure
Lambda expressions can access outer scope variables and arguments. This isoften called a closure. Example where "i" and "a:arg" are used in a lambdawhile they already exist in the function scope. They remain valid even afterthe function returns:

:function Foo(arg):  let i = 3:  return {x -> x + i - a:arg}:endfunction:let Bar = Foo(4):echo Bar(6)

5Note that the variables must exist in the outer scope before the lambda isdefined for this to work. See also:func-closure.

Lambda and closure support can be checked with:

if has('lambda')

Examples for using a lambda expression withsort(),map() andfilter():

:echo map([1, 2, 3], {idx, val -> val + 1})

[2, 3, 4]

:echo sort([3,7,2,1,4], {a, b -> a - b})

[1, 2, 3, 4, 7]

The lambda expression is also useful for jobs and timers:

:let timer = timer_start(500,                \ {-> execute("echo 'Handler called'", "")},                \ {'repeat': 3})

Handler calledHandler calledHandler called

Note that it is possible to cause memory to be used and not freed if theclosure is referenced by the context it depends on:

function Function()   let x = 0   let F = {-> x} endfunction

The closure uses "x" from the function scope, and "F" in that same scoperefers to the closure. This cycle results in the memory not being freed.Recommendation: don't do this.

Notice how execute() is used to execute an Ex command. That's ugly though.

Lambda expressions have internal names like '<lambda>42'. If you get an errorfor a lambda expression, you can find what it is with the following command:

:function <lambda>42

3. Internal variableinternal-variablesE461

An internal variable name can be made up of letters, digits and '_'. But itcannot start with a digit. It's also possible to use curly braces, seecurly-braces-names.

An internal variable is created with the ":let" command:let.An internal variable is explicitly destroyed with the ":unlet" command:unlet.Using a name that is not an internal variable or refers to a variable that hasbeen destroyed results in an error.

variable-scope
There are several name spaces for variables. Which one is to be used isspecified by what is prepended:

(nothing) In a function: local to a function; otherwise: globalbuffer-variable b: Local to the current buffer.window-variable w: Local to the current window.tabpage-variable t: Local to the current tab page.global-variable g: Global.local-variable l: Local to a function.script-variable s: Local to a:sourced Vim script.function-argument a: Function argument (only inside a function).vim-variable v: Global, predefined by Vim.

The scope name by itself can be used as aDictionary. For example, todelete all script-local variables:

:for k in keys(s:):    unlet s:[k]:endfor

buffer-variableb:varb:A variable name that is preceded with "b:" is local to the current buffer.Thus you can have several "b:foo" variables, one for each buffer.This kind of variable is deleted when the buffer is wiped out or deleted with:bdelete.

One local buffer variable is predefined:b:changedtickchangetickb:changedtickThe total number of changes to the current buffer. It isincremented for each change. An undo command is also a changein this case. Resetting'modified' when writing the buffer isalso counted.This can be used to perform an action only when the buffer haschanged. Example:

:if my_changedtick != b:changedtick:let my_changedtick = b:changedtick:call My_Update():endif

You cannot change or delete the b:changedtick variable.

window-variablew:varw:A variable name that is preceded with "w:" is local to the current window. Itis deleted when the window is closed.

tabpage-variablet:vart:A variable name that is preceded with "t:" is local to the current tab page,It is deleted when the tab page is closed.

global-variableg:varg:Inside functions global variables are accessed with "g:". Omitting this willaccess a variable local to a function. But "g:" can also be used in any otherplace if you like.

local-variablel:varl:Inside functions local variables are accessed without prepending anything.But you can also prepend "l:" if you like. However, without prepending "l:"you may run into reserved variable names. For example "count". By itself itrefers to "v:count". Using "l:count" you can have a local variable with thesame name.

script-variables:varIn a Vim script variables starting with "s:" can be used. They cannot beaccessed from outside of the scripts, thus are local to the script.

They can be used in:

commands executed while the script is sourced

functions defined in the script

autocommands defined in the script

functions and autocommands defined in functions and autocommands which were defined in the script (recursively)

user defined commands defined in the scriptThus not in:

other scripts sourced from this one

mappings

menus

etc.

Script variables can be used to avoid conflicts with global variable names.Take this example:

let s:counter = 0function MyCounter()  let s:counter = s:counter + 1  echo s:counterendfunctioncommand Tick call MyCounter()

You can now invoke "Tick" from any script, and the "s:counter" variable inthat script will not be changed, only the "s:counter" in the script where"Tick" was defined is used.

Another example that does the same:

let s:counter = 0command Tick let s:counter = s:counter + 1 | echo s:counter

When calling a function and invoking a user-defined command, the context forscript variables is set to the script where the function or command wasdefined.

The script variables are also available when a function is defined inside afunction that is defined in a script. Example:

let s:counter = 0function StartCounting(incr)  if a:incr    function MyCounter()      let s:counter = s:counter + 1    endfunction  else    function MyCounter()      let s:counter = s:counter - 1    endfunction  endifendfunction

This defines the MyCounter() function either for counting up or counting downwhen calling StartCounting(). It doesn't matter from where StartCounting() iscalled, the s:counter variable will be accessible in MyCounter().

When the same script is sourced again it will use the same script variables.They will remain valid as long as Vim is running. This can be used tomaintain a counter:

if !exists("s:counter")  let s:counter = 1  echo "script executed for the first time"else  let s:counter = s:counter + 1  echo "script executed " .. s:counter .. " times now"endif

Note that this means that filetype plugins don't get a different set of scriptvariables for each buffer. Use local buffer variables insteadb:var.

PREDEFINED VIM VARIABLESvim-variablev:varv:

E963

The alphabetic list of all builtin variables and details are in a separatehelp file:vvars.

4. Builtin Functionsvim-functionfunctions

The Vimscript subsystem (referred to as "eval" internally) provides builtinfunctions. Scripts can also defineuser-functions.

Seefunction-list to browse functions by topic.

The alphabetic list of all builtin functions and details are in a separatehelp file:builtin-functions.

5. Defining functionsuser-function

New functions can be defined. These can be called just like builtinfunctions. The function takes arguments, executes a sequence of Ex commandsand can return a value.

You can find most information about defining functions inuserfunc.txt.

6. Curly braces namescurly-braces-names

In most places where you can use a variable, you can use a "curly braces name"variable. This is a regular variable name with one or more expressionswrapped in braces {} like this:

my_{adjective}_variable

When Vim encounters this, it evaluates the expression inside the braces, putsthat in place of the expression, and re-interprets the whole as a variablename. So in the above example, if the variable "adjective" was set to"noisy", then the reference would be to "my_noisy_variable", whereas if"adjective" was set to "quiet", then it would be to "my_quiet_variable".

One application for this is to create a set of variables governed by an optionvalue. For example, the statement

echo my_{&background}_message

would output the contents of "my_dark_message" or "my_light_message" dependingon the current value of'background'.

You can use multiple brace pairs:

echo my_{adverb}_{adjective}_message

..or even nest them:

echo my_{ad{end_of_word}}_message

where "end_of_word" is either "verb" or "jective".

However, the expression inside the braces must evaluate to a valid singlevariable name, e.g. this is invalid:

:let foo='a + b':echo c{foo}d

.. since the result of expansion is "ca + bd", which is not a variable name.

curly-braces-function-names
You can call and define functions by an evaluated name in a similar way.Example:

:let func_end='whizz':call my_func_{func_end}(parameter)

This would call the function "my_func_whizz(parameter)".

This does NOT work:

:let i = 3:let @{i} = ''  " error:echo @{i}      " error

7. Commandsexpression-commands

:let{var-name} ={expr1}:letE18Set internal variable{var-name} to the result of theexpression{expr1}. The variable will get the typefrom the{expr}. If{var-name} didn't exist yet, itis created.

:let{var-name}[{idx}] ={expr1}E689
Set a list item to the result of the expression{expr1}.{var-name} must refer to a list and{idx}must be a valid index in that list. For nested listthe index can be repeated.This cannot be used to add an item to aList.This cannot be used to set a byte in a String. Youcan do that like this:

:let var = var[0:2] .. 'X' .. var[4:]

When{var-name} is aBlob then{idx} can be thelength of the blob, in which case one byte isappended.

E711E719:let{var-name}[{idx1}:{idx2}] ={expr1}E708E709E710Set a sequence of items in aList to the result ofthe expression{expr1}, which must be a list with thecorrect number of items.{idx1} can be omitted, zero is used instead.{idx2} can be omitted, meaning the end of the list.When the selected range of items is partly past theend of the list, items will be added.

:let+=:let-=:letstar=:let/=:let%=:let.=:let..=E734:let{var} +={expr1}Like ":let{var} ={var} +{expr1}".:let{var} -={expr1}Like ":let{var} ={var} -{expr1}".:let {var} *= {expr1} Like ":let{var} ={var} *{expr1}".:let{var} /={expr1}Like ":let{var} ={var} /{expr1}".:let{var} %={expr1}Like ":let{var} ={var} %{expr1}".:let{var} .={expr1}Like ":let{var} ={var} .{expr1}".:let{var} ..={expr1}Like ":let{var} ={var} ..{expr1}".These fail if{var} was not set yet and when the typeof{var} and{expr1} don't fit the operator.+= modifies aList or aBlob in-place instead ofcreating a new one.

:let ${env-name} ={expr1}:let-environment:let-$Set environment variable{env-name} to the result ofthe expression{expr1}. The type is always String.:let ${env-name} .={expr1}Append{expr1} to the environment variable{env-name}.If the environment variable didn't exist yet thisworks like "=".

:let @{reg-name} ={expr1}:let-register:let-@Write the result of the expression{expr1} in register{reg-name}.{reg-name} must be a single letter, andmust be the name of a writable register (seeregisters). "@@" can be used for the unnamedregister, "@/" for the search pattern.If the result of{expr1} ends in a<CR> or<NL>, theregister will be linewise, otherwise it will be set tocharwise.This can be used to clear the last search pattern:

:let @/ = ""

This is different from searching for an empty string,that would match everywhere.

:let @{reg-name} .={expr1}Append{expr1} to register{reg-name}. If theregister was empty it's like setting it to{expr1}.

:let &{option-name} ={expr1}:let-option:let-&Set option{option-name} to the result of theexpression{expr1}. A String or Number value isalways converted to the type of the option.For an option local to a window or buffer the effectis just like using the:set command: both the localvalue and the global value are changed.Example:

:let &path = &path .. ',/usr/local/include'

:let &{option-name} .={expr1}For a string option: Append{expr1} to the value.Does not insert a comma like:set+=.

:let &{option-name} +={expr1}:let &{option-name} -={expr1}For a number or boolean option: Add or subtract{expr1}.

:let &l:{option-name} ={expr1}:let &l:{option-name} .={expr1}:let &l:{option-name} +={expr1}:let &l:{option-name} -={expr1}Like above, but only set the local value of an option(if there is one). Works like:setlocal.

:let &g:{option-name} ={expr1}:let &g:{option-name} .={expr1}:let &g:{option-name} +={expr1}:let &g:{option-name} -={expr1}Like above, but only set the global value of an option(if there is one). Works like:setglobal.

:let [{name1},{name2}, ...] ={expr1}:let-unpackE687E688{expr1} must evaluate to aList. The first item inthe list is assigned to{name1}, the second item to{name2}, etc.The number of names must match the number of items intheList.Each name can be one of the items of the ":let"command as mentioned above.Example:

:let [s, item] = GetItem(s)

Detail:{expr1} is evaluated first, then theassignments are done in sequence. This matters if{name2} depends on{name1}. Example:

:let x = [0, 1]:let i = 0:let [i, x[i]] = [1, 2]:echo x

The result is [0, 2].

:let [{name1},{name2}, ...] .={expr1}:let [{name1},{name2}, ...] +={expr1}:let [{name1},{name2}, ...] -={expr1}Like above, but append/add/subtract the value for eachList item.

:let [{name}, ..., ;{lastname}] ={expr1}E452
Like:let-unpack above, but theList may have moreitems than there are names. A list of the remainingitems is assigned to{lastname}. If there are noremaining items{lastname} is set to an empty list.Example:

:let [a, b; rest] = ["aval", "bval", 3, 4]

:let [{name}, ..., ;{lastname}] .={expr1}:let [{name}, ..., ;{lastname}] +={expr1}:let [{name}, ..., ;{lastname}] -={expr1}Like above, but append/add/subtract the value for eachList item.

:let=<<:let-heredocE990E991E172E221E1145:let{var-name} =<< [trim] [eval]{endmarker}text...text...{endmarker}Set internal variable{var-name} to aListcontaining the lines of text bounded by the string{endmarker}.

If "eval" is not specified, then each line of text isused as aliteral-string, except that single quotesdoes not need to be doubled.If "eval" is specified, then any Vim expression in theform{expr} is evaluated and the result replaces theexpression, like withinterpolated-string.Example where $HOME is expanded:

let lines =<< trim eval END  some text  See the file {$HOME}/.vimrc  more textEND

There can be multiple Vim expressions in a single linebut an expression cannot span multiple lines. If anyexpression evaluation fails, then the assignment fails.

{endmarker} must not contain white space.{endmarker} cannot start with a lower case character.The last line should end only with the{endmarker}string without any other character. Watch out forwhite space after{endmarker}!

Without "trim" any white space characters in the linesof text are preserved. If "trim" is specified before{endmarker}, then indentation is stripped so you cando:

let text =<< trim END   if ok     echo 'done'   endifEND

Results in:["if ok", " echo 'done'", "endif"]The marker must line up with "let" and the indentationof the first line is removed from all the text lines.Specifically: all the leading indentation exactlymatching the leading indentation of the firstnon-empty text line is stripped from the input lines.All leading indentation exactly matching the leadingindentation beforelet is stripped from the linecontaining{endmarker}. Note that the differencebetween space and tab matters here.

If{var-name} didn't exist yet, it is created.Cannot be followed by another command, but can befollowed by a comment.

To avoid line continuation to be applied, consideradding 'C' to'cpoptions':

set cpo+=Clet var =<< END   \ leading backslashENDset cpo-=C

Examples:

let var1 =<< ENDSample text 1    Sample text 2Sample text 3ENDlet data =<< trim DATA        1 2 3 4        5 6 7 8DATAlet code =<< trim eval CODE   let v = {10 + 20}   let h = "{$HOME}"   let s = "{Str1()} abc {Str2()}"   let n = {MyFunc(3, 4)}CODE

E121
:let{var-name}..List the value of variable{var-name}. Multiplevariable names may be given. Special names recognizedhere:E738
g:global variables b:local buffer variables w:local window variables t:local tab page variables s:script-local variables l:local function variables v:Vim variables.

:letList the values of all variables. The type of thevariable is indicated before the value:<nothing>String#Number*Funcref

:unl[et][!]{name} ...:unlet:unlE108E795Remove the internal variable{name}. Several variablenames can be given, they are all removed. The namemay also be aList orDictionary item.With [!] no error message is given for non-existingvariables.One or more items from aList can be removed:

:unlet list[3]  " remove fourth item:unlet list[3:]   " remove fourth item to last

One item from aDictionary can be removed at a time:

:unlet dict['two']:unlet dict.two

This is especially useful to clean up used globalvariables and script-local variables (these are notdeleted when the script ends). Function-localvariables are automatically deleted when the functionends.

:unl[et] ${env-name} ...:unlet-environment:unlet-$Remove environment variable{env-name}.Can mix{name} and ${env-name} in one :unlet command.No error message is given for a non-existingvariable, also without !.If the system does not support deleting an environmentvariable, it is made empty.

:cons:const:cons[t]{var-name} ={expr1}:cons[t] [{name1},{name2}, ...] ={expr1}:cons[t] [{name}, ..., ;{lastname}] ={expr1}:cons[t]{var-name} =<< [trim] [eval]{marker}text...text...{marker}Similar to:let, but additionally lock the variableafter setting the value. This is the same as lockingthe variable with:lockvar just after:let, thus:

:const x = 1

is equivalent to:

:let x = 1:lockvar! x

This is useful if you want to make sure the variableis not modified. If the value is a List or Dictionaryliteral then the items also cannot be changed:

const ll = [1, 2, 3]let ll[1] = 5  " Error!

Nested references are not locked:

let lvar = ['a']const lconst = [0, lvar]let lconst[0] = 2  " Error!let lconst[1][0] = 'b'  " OK

E995
It is an error to specify an existing variable with:const.

:let x = 1:const x = 1  " Error!

E996
Note that environment variables, option values andregister values cannot be used here, since they cannotbe locked.

:cons[t]:cons[t]{var-name}If no argument is given or only{var-name} is given,the behavior is the same as:let.

:lockv[ar][!] [depth]{name} ...:lockvar:lockvLock the internal variable{name}. Locking means thatit can no longer be changed (until it is unlocked).A locked variable can be deleted:

:lockvar v:let v = 'asdf'  " fails!:unlet v  " works

E741E940E1122If you try to change a locked variable you get anerror message: "E741: Value is locked:{name}".If you try to lock or unlock a built-in variable youwill get an error message "E940: Cannot lock or unlockvariable{name}".

[depth] is relevant when locking aList orDictionary. It specifies how deep the locking goes:0Lock the variable{name} but not itsvalue.1Lock theList orDictionary itself,cannot add or remove items, but canstill change their values.2Also lock the values, cannot changethe items. If an item is aList orDictionary, cannot add or removeitems, but can still change thevalues.3Like 2 but for theList /Dictionary in theList /Dictionary, one level deeper.The default [depth] is 2, thus when{name} is aListorDictionary the values cannot be changed.

Example with [depth] 0:

let mylist = [1, 2, 3]lockvar 0 mylistlet mylist[0] = 77" OKcall add(mylist, 4)" OKlet mylist = [7, 8, 9]  " Error!

E743
For unlimited depth use [!] and omit [depth].However, there is a maximum depth of 100 to catchloops.

Note that when two variables refer to the sameListand you lock one of them, theList will also belocked when used through the other variable.Example:

:let l = [0, 1, 2, 3]:let cl = l:lockvar l:let cl[1] = 99" won't work!

You may want to make a copy of a list to avoid this.Seedeepcopy().

:unlo[ckvar][!] [depth]{name} ...:unlockvar:unloUnlock the internal variable{name}. Does theopposite of:lockvar.

No error is given if{name} does not exist.

:if{expr1}:if:end:endif:enE171E579E580:en[dif]Execute the commands until the next matching:elseor:endif if{expr1} evaluates to non-zero.Although the short forms work, it is recommended toalways use:endif to avoid confusion and to makeauto-indenting work properly.

From Vim version 4.5 until 5.0, every Ex command inbetween the:if and:endif is ignored. These twocommands were just to allow for future expansions in abackward compatible way. Nesting was allowed. Notethat any:else or:elseif was ignored, theelsepart was not executed either.

You can use this to remain compatible with olderversions:

:if version >= 500:  version-5-specific-commands:endif

The commands still need to be parsed to find theendif. Sometimes an older Vim has a problem with anew command. For example,:silent is recognized asa:substitute command. In that case:execute canavoid problems:

:if version >= 600:  execute "silent 1,$delete":endif

NOTE: The:append and:insert commands don't workproperly in between:if and:endif.

:else:elE581E583:el[se]Execute the commands until the next matching:elseor:endif if they previously were not beingexecuted.

:elseif:elseiE582E584:elsei[f]{expr1}Short for:else:if, with the addition that thereis no extra:endif.

:wh[ile]{expr1}:while:endwhile:wh:endwE170E585E588E733:endw[hile]Repeat the commands between:while and:endwhile,as long as{expr1} evaluates to non-zero.When an error is detected from a command inside theloop, execution continues after theendwhile.Example:

:let lnum = 1:while lnum <= line("$")   :call FixLine(lnum)   :let lnum = lnum + 1:endwhile

NOTE: The:append and:insert commands don't workproperly inside a:while and:for loop.

:for{var} in{object}:forE690E732:endfo[r]:endfo:endforRepeat the commands between:for and:endfor foreach item in{object}.{object} can be aList,aBlob or aString.

Variable{var} is set to the value of each item.

When an error is detected for a command inside theloop, execution continues after theendfor.Changing{object} inside the loop affects what itemsare used. Make a copy if this is unwanted:

:for item in copy(mylist)

When{object} is aList and not making a copy, Vimstores a reference to the next item in theListbefore executing the commands with the current item.Thus the current item can be removed without effect.Removing any later item means it will not be found.Thus the following example works (an inefficient wayto make aList empty):

for item in mylist   call remove(mylist, 0)endfor

Note that reordering theList (e.g., with sort() orreverse()) may have unexpected effects.

When{object} is aBlob, Vim always makes a copy toiterate over. Unlike withList, modifying theBlob does not affect the iteration.

When{object} is aString each item is a string withone character, plus any combining characters.

:for [{var1},{var2}, ...] in{listlist}:endfo[r]Like:for above, but each item in{listlist} must bea list, of which each item is assigned to{var1},{var2}, etc. Example:

:for [lnum, col] in [[1, 3], [2, 5], [3, 8]]   :echo getline(lnum)[col]:endfor

:continue:conE586:con[tinue]When used inside a:while or:for loop, jumps backto the start of the loop.

If it is used after a:try inside the loop butbefore the matching:finally (if present), thecommands following the:finally up to the matching:endtry are executed first. This process applies toall nested:trys inside the loop. The outermost:endtry then jumps back to the start of the loop.

:break:breaE587:brea[k]When used inside a:while or:for loop, skips tothe command after the matching:endwhile or:endfor.If it is used after a:try inside the loop butbefore the matching:finally (if present), thecommands following the:finally up to the matching:endtry are executed first. This process applies toall nested:trys inside the loop. The outermost:endtry then jumps to the command after the loop.

:try:try:endt:endtryE600E601E602:endt[ry]Change the error handling for the commands between:try and:endtry including everything beingexecuted across:source commands, function calls,or autocommand invocations.

When an error or interrupt is detected and there isa:finally command following, execution continuesafter the:finally. Otherwise, or when the:endtry is reached thereafter, the next(dynamically) surrounding:try is checked fora corresponding:finally etc. Then the scriptprocessing is terminated. Whether a functiondefinition has an "abort" argument does not matter.Example:

try | call Unknown() | finally | echomsg "cleanup" | endtryechomsg "not reached"

Moreover, an error or interrupt (dynamically) inside:try and:endtry is converted to an exception. Itcan be caught as if it were thrown by a:throwcommand (see:catch). In this case, the scriptprocessing is not terminated.

The value "Vim:Interrupt" is used for an interruptexception. An error in a Vim command is convertedto a value of the form "Vim({command}):{errmsg}",other errors are converted to a value of the form"Vim:{errmsg}".{command} is the full command name,and{errmsg} is the message that is displayed if theerror exception is not caught, always beginning withthe error number.Examples:

try | sleep 100 | catch /^Vim:Interrupt$/ | endtrytry | edit | catch /^Vim(edit):E\d\+/ | echo "error" | endtry

:cat:catchE603E604E605:cat[ch] /{pattern}/The following commands until the next:catch,:finally, or:endtry that belongs to the same:try as the:catch are executed when an exceptionmatching{pattern} is being thrown and has not yetbeen caught by a previous:catch. Otherwise, thesecommands are skipped.When{pattern} is omitted all errors are caught.Examples:

:catch /^Vim:Interrupt$/ " catch interrupts (CTRL-C):catch /^Vim\%((\a\+)\)\=:E/ " catch all Vim errors:catch /^Vim\%((\a\+)\)\=:/ " catch errors and interrupts:catch /^Vim(write):/ " catch all errors in :write:catch /^Vim\%((\a\+)\)\=:E123:/ " catch error E123:catch /my-exception/ " catch user exception:catch /.*/ " catch everything:catch " same as /.*/

Another character can be used instead of / around the{pattern}, so long as it does not have a specialmeaning (e.g., '|' or '"') and doesn't occur inside{pattern}.Information about the exception is available inv:exception. Also seethrow-variables.NOTE: It is not reliable to ":catch" the TEXT ofan error message because it may vary in differentlocales.

:fina:finallyE606E607:fina[lly]The following commands until the matching:endtryare executed whenever the part between the matching:try and the:finally is left: either by fallingthrough to the:finally or by a:continue,:break,:finish, or:return, or by an error orinterrupt or exception (see:throw).

:th:throwE608:th[row]{expr1}The{expr1} is evaluated and thrown as an exception.If the:throw is used after a:try but before thefirst corresponding:catch, commands are skippeduntil the first:catch matching{expr1} is reached.If there is no such:catch or if the:throw isused after a:catch but before the:finally, thecommands following the:finally (if present) up tothe matching:endtry are executed. If the:throwis after the:finally, commands up to the:endtryare skipped. At the:endtry, this process appliesagain for the next dynamically surrounding:try(which may be found in a calling function or sourcingscript), until a matching:catch has been found.If the exception is not caught, the command processingis terminated.Example:

:try | throw "oops" | catch /^oo/ | echo "caught" | endtry

Note that "catch" may need to be on a separate linefor when an error causes the parsing to skip the wholeline and not see the "|" that separates the commands.

:ec:echo:ec[ho]{expr1} ..Echoes each{expr1}, with a space in between. Thefirst{expr1} starts on a new line.Also see:comment.Use "\n" to start a new line. Use "\r" to move thecursor to the first column.Uses the highlighting set by the:echohl command.Cannot be followed by a comment.Example:

:echo "the value of 'shell' is" &shell

:echo-redraw
A later redraw may make the message disappear again.And since Vim mostly postpones redrawing until it'sfinished with a sequence of commands this happensquite often. To avoid that a command from before the:echo causes a redraw afterwards (redraws are oftenpostponed until you type something), force a redrawwith the:redraw command. Example:

:new | redraw | echo "there is a new window"

:echo-self-refer
When printing nested containers echo prints secondoccurrence of the self-referencing container using"[...@level]" (self-referencingList) or"{...@level}" (self-referencingDict):

:let l = []:call add(l, l):let l2 = []:call add(l2, [l2]):echo l l2

echoes "[[...@0]] [[[...@0]]]". Echoing "[l]" willecho "[[[...@1]]]" because l first occurs at secondlevel.

:echon
:echon{expr1} ..Echoes each{expr1}, without anything added. Also see:comment.Uses the highlighting set by the:echohl command.Cannot be followed by a comment.Example:

:echon "the value of 'shell' is " &shell

Note the difference between using:echo, which is aVim command, and:!echo, which is an external shellcommand:

:!echo %--> filename

The arguments of ":!" are expanded, see:_%.

:!echo "%"--> filename or "filename"

Like the previous example. Whether you see the doublequotes or not depends on your'shell'.

:echo %--> nothing

The '%' is an illegal character in an expression.

:echo "%"--> %

This just echoes the '%' character.

:echo expand("%")--> filename

This calls the expand() function to expand the '%'.

:echoh:echohl:echoh[l]{name}Use the highlight group{name} for the following:echo,:echon and:echomsg commands. Also usedfor theinput() prompt. Example:

:echohl WarningMsg | echo "Don't panic!" | echohl None

Don't forget to set the group back to "None",otherwise all following echo's will be highlighted.

:echom:echomsg:echom[sg]{expr1} ..Echo the expression(s) as a true message, saving themessage in themessage-history.Spaces are placed between the arguments as with the:echo command. But unprintable characters aredisplayed, not interpreted.The parsing works slightly different from:echo,more like:execute. All the expressions are firstevaluated and concatenated before echoing anything.If expressions does not evaluate to a Number orString, string() is used to turn it into a string.Uses the highlighting set by the:echohl command.Example:

:echomsg "It's a Zizzer Zazzer Zuzz, as you can plainly see."

See:echo-redraw to avoid the message disappearingwhen the screen is redrawn.:echoe:echoerr:echoe[rr]{expr1} ..Echo the expression(s) as an error message, saving themessage in themessage-history. When used in ascript or function the line number will be added.Spaces are placed between the arguments as with the:echomsg command. When used inside a try conditional,the message is raised as an error exception instead(seetry-echoerr).Example:

:echoerr "This script just failed!"

If you just want a highlighted message use:echohl.And to get a beep:

:exe "normal \<Esc>"

:eval
:eval{expr}Evaluate{expr} and discard the result. Example:

:eval Getlist()->Filter()->append('$')

The expression is supposed to have a side effect,since the resulting value is not used. In the exampletheappend() call appends the List with text to thebuffer. This is similar to:call but works with anyexpression.

The command can be shortened to:ev or:eva, butthese are hard to recognize and therefore not to beused.

The command cannot be followed by "|" and anothercommand, since "|" is seen as part of the expression.

:exe:execute:exe[cute]{expr1} ..Executes the string that results from the evaluationof{expr1} as an Ex command.Multiple arguments are concatenated, with a space inbetween. To avoid the extra space use the ".."operator to concatenate strings into one argument.{expr1} is used as the processed command, command lineediting keys are not recognized.Cannot be followed by a comment.Examples:

:execute "buffer" nextbuf:execute "normal" count .. "w"

":execute" can be used to append a command to commandsthat don't accept a '|'. Example:

:execute '!ls' | echo "theend"

":execute" is also a nice way to avoid having to typecontrol characters in a Vim script for a ":normal"command:

:execute "normal ixxx\<Esc>"

This has an<Esc> character, seeexpr-string.

Be careful to correctly escape special characters infile names. Thefnameescape() function can be usedfor Vim commands,shellescape() for:! commands.Examples:

:execute "e " .. fnameescape(filename):execute "!ls " .. shellescape(filename, 1)

Note: The executed string may be any command-line, butstarting or ending "if", "while" and "for" does notalways work, because when commands are skipped the":execute" is not evaluated and Vim loses track ofwhere blocks start and end. Also "break" and"continue" should not be inside ":execute".This example does not work, because the ":execute" isnot evaluated and Vim does not see the "while", andgives an error for finding an ":endwhile":

:if 0: execute 'while i > 5':  echo "test": endwhile:endif

It is allowed to have a "while" or "if" commandcompletely in the executed string:

:execute 'while i < 5 | echo i | let i = i + 1 | endwhile'

:exe-comment
":execute", ":echo" and ":echon" cannot be followed bya comment directly, because they see the '"' as thestart of a string. But, you can use '|' followed by acomment. Example:

:echo "foo" | "this is a comment

8. Exception handlingexception-handling

The Vim script language comprises an exception handling feature. This sectionexplains how it can be used in a Vim script.

Exceptions may be raised by Vim on an error or on interrupt, seecatch-errors andcatch-interrupt. You can also explicitly throw anexception by using the ":throw" command, seethrow-catch.

TRY CONDITIONALStry-conditionals

Exceptions can be caught or can cause cleanup code to be executed. You canuse a try conditional to specify catch clauses (that catch exceptions) and/ora finally clause (to be executed for cleanup). A try conditional begins with a:try command and ends at the matching:endtry command. In between, you can use a:catch command to starta catch clause, or a:finally command to start a finally clause. There maybe none or multiple catch clauses, but there is at most one finally clause,which must not be followed by any catch clauses. The lines before the catchclauses and the finally clause is called a try block.

:try:...:...TRY BLOCK:...:catch /{pattern}/:...:...CATCH CLAUSE:...:catch /{pattern}/:...:...CATCH CLAUSE:...:finally:...:...FINALLY CLAUSE:...:endtry

The try conditional allows to watch code for exceptions and to take theappropriate actions. Exceptions from the try block may be caught. Exceptionsfrom the try block and also the catch clauses may cause cleanup actions. When no exception is thrown during execution of the try block, the controlis transferred to the finally clause, if present. After its execution, thescript continues with the line following the ":endtry". When an exception occurs during execution of the try block, the remaininglines in the try block are skipped. The exception is matched against thepatterns specified as arguments to the ":catch" commands. The catch clauseafter the first matching ":catch" is taken, other catch clauses are notexecuted. The catch clause ends when the next ":catch", ":finally", or":endtry" command is reached - whatever is first. Then, the finally clause(if present) is executed. When the ":endtry" is reached, the script executioncontinues in the following line as usual. When an exception that does not match any of the patterns specified by the":catch" commands is thrown in the try block, the exception is not caught bythat try conditional and none of the catch clauses is executed. Only thefinally clause, if present, is taken. The exception pends during execution ofthe finally clause. It is resumed at the ":endtry", so that commands afterthe ":endtry" are not executed and the exception might be caught elsewhere,seetry-nesting. When during execution of a catch clause another exception is thrown, theremaining lines in that catch clause are not executed. The new exception isnot matched against the patterns in any of the ":catch" commands of the sametry conditional and none of its catch clauses is taken. If there is, however,a finally clause, it is executed, and the exception pends during itsexecution. The commands following the ":endtry" are not executed. The newexception might, however, be caught elsewhere, seetry-nesting. When during execution of the finally clause (if present) an exception isthrown, the remaining lines in the finally clause are skipped. If the finallyclause has been taken because of an exception from the try block or one of thecatch clauses, the original (pending) exception is discarded. The commandsfollowing the ":endtry" are not executed, and the exception from the finallyclause is propagated and can be caught elsewhere, seetry-nesting.

The finally clause is also executed, when a ":break" or ":continue" fora ":while" loop enclosing the complete try conditional is executed from thetry block or a catch clause. Or when a ":return" or ":finish" is executedfrom the try block or a catch clause of a try conditional in a function orsourced script, respectively. The ":break", ":continue", ":return", or":finish" pends during execution of the finally clause and is resumed when the":endtry" is reached. It is, however, discarded when an exception is thrownfrom the finally clause. When a ":break" or ":continue" for a ":while" loop enclosing the completetry conditional or when a ":return" or ":finish" is encountered in the finallyclause, the rest of the finally clause is skipped, and the ":break",":continue", ":return" or ":finish" is executed as usual. If the finallyclause has been taken because of an exception or an earlier ":break",":continue", ":return", or ":finish" from the try block or a catch clause,this pending exception or command is discarded.

For examples seethrow-catch andtry-finally.

NESTING OF TRY CONDITIONALStry-nesting

Try conditionals can be nested arbitrarily. That is, a complete tryconditional can be put into the try block, a catch clause, or the finallyclause of another try conditional. If the inner try conditional does notcatch an exception thrown in its try block or throws a new exception from oneof its catch clauses or its finally clause, the outer try conditional ischecked according to the rules above. If the inner try conditional is in thetry block of the outer try conditional, its catch clauses are checked, butotherwise only the finally clause is executed. It does not matter fornesting, whether the inner try conditional is directly contained in the outerone, or whether the outer one sources a script or calls a function containingthe inner try conditional.

When none of the active try conditionals catches an exception, just theirfinally clauses are executed. Thereafter, the script processing terminates.An error message is displayed in case of an uncaught exception explicitlythrown by a ":throw" command. For uncaught error and interrupt exceptionsimplicitly raised by Vim, the error message(s) or interrupt message are shownas usual.

For examples seethrow-catch.

EXAMINING EXCEPTION HANDLING CODEexcept-examine

Exception handling code can get tricky. If you are in doubt what happens, set'verbose' to 13 or use the ":13verbose" command modifier when sourcing yourscript file. Then you see when an exception is thrown, discarded, caught, orfinished. When using a verbosity level of at least 14, things pending ina finally clause are also shown. This information is also given in debug mode(seedebug-scripts).

THROWING AND CATCHING EXCEPTIONSthrow-catch

You can throw any number or string as an exception. Use the:throw commandand pass the value to be thrown as argument:

:throw 4711:throw "string"

throw-expression
You can also specify an expression argument. The expression is then evaluatedfirst, and the result is thrown:

:throw 4705 + strlen("string"):throw strpart("strings", 0, 6)

An exception might be thrown during evaluation of the argument of the ":throw"command. Unless it is caught there, the expression evaluation is abandoned.The ":throw" command then does not throw a new exception. Example:

:function! Foo(arg):  try:    throw a:arg:  catch /foo/:  endtry:  return 1:endfunction::function! Bar():  echo "in Bar":  return 4710:endfunction::throw Foo("arrgh") + Bar()

This throws "arrgh", and "in Bar" is not displayed since Bar() is notexecuted.

:throw Foo("foo") + Bar()

however displays "in Bar" and throws 4711.

Any other command that takes an expression as argument might also beabandoned by an (uncaught) exception during the expression evaluation. Theexception is then propagated to the caller of the command. Example:

:if Foo("arrgh"):  echo "then":else:  echo "else":endif

Here neither of "then" or "else" is displayed.

catch-order
Exceptions can be caught by a try conditional with one or more:catchcommands, seetry-conditionals. The values to be caught by each ":catch"command can be specified as a pattern argument. The subsequent catch clausegets executed when a matching exception is caught. Example:

:function! Foo(value):  try:    throw a:value:  catch /^\d\+$/:    echo "Number thrown":  catch /.*/:    echo "String thrown":  endtry:endfunction::call Foo(0x1267):call Foo('string')

The first call to Foo() displays "Number thrown", the second "String thrown".An exception is matched against the ":catch" commands in the order they arespecified. Only the first match counts. So you should place the morespecific ":catch" first. The following order does not make sense:

:  catch /.*/:    echo "String thrown":  catch /^\d\+$/:    echo "Number thrown"

The first ":catch" here matches always, so that the second catch clause isnever taken.

throw-variables
If you catch an exception by a general pattern, you may access the exact valuein the variablev:exception:

:  catch /^\d\+$/:    echo "Number thrown.  Value is" v:exception

You may also be interested where an exception was thrown. This is stored inv:throwpoint. And you can obtain the stack trace fromv:stacktrace.Note that "v:exception", "v:stacktrace" and "v:throwpoint" are valid for theexception most recently caught as long it is not finished. Example:

:function! Caught():  if v:exception != "":    echo 'Caught "' .. v:exception .. '" in ' .. v:throwpoint:  else:    echo 'Nothing caught':  endif:endfunction::function! Foo():  try:    try:      try: throw 4711:      finally: call Caught():      endtry:    catch /.*/:      call Caught():      throw "oops":    endtry:  catch /.*/:    call Caught():  finally:    call Caught():  endtry:endfunction::call Foo()

This displays

Nothing caughtCaught "4711" in function Foo, line 4Caught "oops" in function Foo, line 10Nothing caught

A practical example: The following command ":LineNumber" displays the linenumber in the script or function where it has been used:

:function! LineNumber():    return substitute(v:throwpoint, '.*\D\(\d\+\).*', '\1', ""):endfunction:command! LineNumber try | throw "" | catch | echo LineNumber() | endtry

try-nested
An exception that is not caught by a try conditional can be caught bya surrounding try conditional:

:try:  try:    throw "foo":  catch /foobar/:    echo "foobar":  finally:    echo "inner finally":  endtry:catch /foo/:  echo "foo":endtry

The inner try conditional does not catch the exception, just its finallyclause is executed. The exception is then caught by the outer tryconditional. The example displays "inner finally" and then "foo".

throw-from-catch
You can catch an exception and throw a new one to be caught elsewhere from thecatch clause:

:function! Foo():  throw "foo":endfunction::function! Bar():  try:    call Foo():  catch /foo/:    echo "Caught foo, throw bar":    throw "bar":  endtry:endfunction::try:  call Bar():catch /.*/:  echo "Caught" v:exception:endtry

This displays "Caught foo, throw bar" and then "Caught bar".

rethrow
There is no real rethrow in the Vim script language, but you may throw"v:exception" instead:

:function! Bar():  try:    call Foo():  catch /.*/:    echo "Rethrow" v:exception:    throw v:exception:  endtry:endfunction

try-echoerr
Note that this method cannot be used to "rethrow" Vim error or interruptexceptions, because it is not possible to fake Vim internal exceptions.Trying so causes an error exception. You should throw your own exceptiondenoting the situation. If you want to cause a Vim error exception containingthe original error exception value, you can use the:echoerr command:

:try:  try:    asdf:  catch /.*/:    echoerr v:exception:  endtry:catch /.*/:  echo v:exception:endtry

This code displays

Vim(echoerr):Vim:E492: Not an editor command:asdf

CLEANUP CODEtry-finally

Scripts often change global settings and restore them at their end. If theuser however interrupts the script by pressingCTRL-C, the settings remain inan inconsistent state. The same may happen to you in the development phase ofa script when an error occurs or you explicitly throw an exception withoutcatching it. You can solve these problems by using a try conditional witha finally clause for restoring the settings. Its execution is guaranteed onnormal control flow, on error, on an explicit ":throw", and on interrupt.(Note that errors and interrupts from inside the try conditional are convertedto exceptions. When not caught, they terminate the script after the finallyclause has been executed.)Example:

:try:  let s:saved_ts = &ts:  set ts=17::  " Do the hard work here.::finally:  let &ts = s:saved_ts:  unlet s:saved_ts:endtry

This method should be used locally whenever a function or part of a scriptchanges global settings which need to be restored on failure or normal exit ofthat function or script part.

break-finally
Cleanup code works also when the try block or a catch clause is left bya ":continue", ":break", ":return", or ":finish". Example:

:let first = 1:while 1:  try:    if first:      echo "first":      let first = 0:      continue:    else:      throw "second":    endif:  catch /.*/:    echo v:exception:    break:  finally:    echo "cleanup":  endtry:  echo "still in while":endwhile:echo "end"

This displays "first", "cleanup", "second", "cleanup", and "end".

:function! Foo():  try:    return 4711:  finally:    echo "cleanup\n":  endtry:  echo "Foo still active":endfunction::echo Foo() "returned by Foo"

This displays "cleanup" and "4711 returned by Foo". You don't need to add anextra ":return" in the finally clause. (Above all, this would override thereturn value.)

except-from-finally
Using either of ":continue", ":break", ":return", ":finish", or ":throw" ina finally clause is possible, but not recommended since it abandons thecleanup actions for the try conditional. But, of course, interrupt and errorexceptions might get raised from a finally clause. Example where an error in the finally clause stops an interrupt fromworking correctly:

:try:  try:    echo "Press CTRL-C for interrupt":    while 1:    endwhile:  finally:    unlet novar:  endtry:catch /novar/:endtry:echo "Script still running":sleep 1

If you need to put commands that could fail into a finally clause, you shouldthink about catching or ignoring the errors in these commands, seecatch-errors andignore-errors.

CATCHING ERRORScatch-errors

If you want to catch specific errors, you just have to put the code to bewatched in a try block and add a catch clause for the error message. Thepresence of the try conditional causes all errors to be converted to anexception. No message is displayed andv:errmsg is not set then. To findthe right pattern for the ":catch" command, you have to know how the format ofthe error exception is. Error exceptions have the following format:

Vim({cmdname}):{errmsg}

Vim:{errmsg}

{cmdname} is the name of the command that failed; the second form is used whenthe command name is not known.{errmsg} is the error message usually producedwhen the error occurs outside try conditionals. It always begins witha capital "E", followed by a two or three-digit error number, a colon, anda space.

Examples:

The command

:unlet novar

normally produces the error message

E108: No such variable: "novar"

which is converted inside try conditionals to an exception

Vim(unlet):E108: No such variable: "novar"

The command

:dwim

normally produces the error message

E492: Not an editor command: dwim

which is converted inside try conditionals to an exception

Vim:E492: Not an editor command: dwim

You can catch all ":unlet" errors by a

:catch /^Vim(unlet):/

or all errors for misspelled command names by a

:catch /^Vim:E492:/

Some error messages may be produced by different commands:

:function nofunc

and

:delfunction nofunc

both produce the error message

E128: Function name must start with a capital: nofunc

which is converted inside try conditionals to an exception

Vim(function):E128: Function name must start with a capital: nofunc

Vim(delfunction):E128: Function name must start with a capital: nofunc

respectively. You can catch the error by its number independently on thecommand that caused it if you use the following pattern:

:catch /^Vim(\a\+):E128:/

Some commands like

:let x = novar

produce multiple error messages, here:

E121: Undefined variable: novarE15: Invalid expression:  novar

Only the first is used for the exception value, since it is the most specificone (seeexcept-several-errors). So you can catch it by

:catch /^Vim(\a\+):E121:/

You can catch all errors related to the name "nofunc" by

:catch /\<nofunc\>/

You can catch all Vim errors in the ":write" and ":read" commands by

:catch /^Vim(\(write\|read\)):E\d\+:/

You can catch all Vim errors by the pattern

:catch /^Vim\((\a\+)\)\=:E\d\+:/

catch-text
NOTE: You should never catch the error message text itself:

:catch /No such variable/

only works in the English locale, but not when the user has selecteda different language by the:language command. It is however helpful tocite the message text in a comment:

:catch /^Vim(\a\+):E108:/   " No such variable

IGNORING ERRORSignore-errors

You can ignore errors in a specific Vim command by catching them locally:

:try:  write:catch:endtry

But you are strongly recommended NOT to use this simple form, since it couldcatch more than you want. With the ":write" command, some autocommands couldbe executed and cause errors not related to writing, for instance:

:au BufWritePre * unlet novar

There could even be such errors you are not responsible for as a scriptwriter: a user of your script might have defined such autocommands. You wouldthen hide the error from the user. It is much better to use

:try:  write:catch /^Vim(write):/:endtry

which only catches real write errors. So catch only what you'd like to ignoreintentionally.

For a single command that does not cause execution of autocommands, you couldeven suppress the conversion of errors to exceptions by the ":silent!"command:

:silent! nunmap k

This works also when a try conditional is active.

CATCHING INTERRUPTScatch-interrupt

When there are active try conditionals, an interrupt (CTRL-C) is converted tothe exception "Vim:Interrupt". You can catch it like every exception. Thescript is not terminated, then. Example:

:function! TASK1():  sleep 10:endfunction:function! TASK2():  sleep 20:endfunction:while 1:  let command = input("Type a command: "):  try:    if command == "":      continue:    elseif command == "END":      break:    elseif command == "TASK1":      call TASK1():    elseif command == "TASK2":      call TASK2():    else:      echo "\nIllegal command:" command:      continue:    endif:  catch /^Vim:Interrupt$/:    echo "\nCommand interrupted":    " Caught the interrupt.  Continue with next prompt.:  endtry:endwhile

You can interrupt a task here by pressingCTRL-C; the script then asks fora new command. If you pressCTRL-C at the prompt, the script is terminated.

For testing what happens whenCTRL-C would be pressed on a specific line inyour script, use the debug mode and execute the>quit or>interruptcommand on that line. Seedebug-scripts.

CATCHING ALLcatch-all

The commands

:catch /.*/:catch //:catch

catch everything, error exceptions, interrupt exceptions and exceptionsexplicitly thrown by the:throw command. This is useful at the top level ofa script in order to catch unexpected things. Example:

:try::  " do the hard work here::catch /MyException/::  " handle known problem::catch /^Vim:Interrupt$/:    echo "Script interrupted":catch /.*/:  echo "Internal error (" .. v:exception .. ")":  echo " - occurred at " .. v:throwpoint:endtry:" end of script

Note: Catching all might catch more things than you want. Thus, you arestrongly encouraged to catch only for problems that you can really handle byspecifying a pattern argument to the ":catch". Example: Catching all could make it nearly impossible to interrupt a scriptby pressingCTRL-C:

:while 1:  try:    sleep 1:  catch:  endtry:endwhile

EXCEPTIONS AND AUTOCOMMANDSexcept-autocmd

Exceptions may be used during execution of autocommands. Example:

:autocmd User x try:autocmd User x   throw "Oops!":autocmd User x catch:autocmd User x   echo v:exception:autocmd User x endtry:autocmd User x throw "Arrgh!":autocmd User x echo "Should not be displayed"::try:  doautocmd User x:catch:  echo v:exception:endtry

This displays "Oops!" and "Arrgh!".

except-autocmd-Pre
For some commands, autocommands get executed before the main action of thecommand takes place. If an exception is thrown and not caught in the sequenceof autocommands, the sequence and the command that caused its execution areabandoned and the exception is propagated to the caller of the command. Example:

:autocmd BufWritePre * throw "FAIL":autocmd BufWritePre * echo "Should not be displayed"::try:  write:catch:  echo "Caught:" v:exception "from" v:throwpoint:endtry

Here, the ":write" command does not write the file currently being edited (asyou can see by checking'modified'), since the exception from the BufWritePreautocommand abandons the ":write". The exception is then caught and thescript displays:

Caught: FAIL from BufWrite Auto commands for "*"

except-autocmd-Post
For some commands, autocommands get executed after the main action of thecommand has taken place. If this main action fails and the command is insidean active try conditional, the autocommands are skipped and an error exceptionis thrown that can be caught by the caller of the command. Example:

:autocmd BufWritePost * echo "File successfully written!"::try:  write /i/m/p/o/s/s/i/b/l/e:catch:  echo v:exception:endtry

This just displays:

Vim(write):E212: Can't open file for writing (/i/m/p/o/s/s/i/b/l/e)

If you really need to execute the autocommands even when the main actionfails, trigger the event from the catch clause. Example:

:autocmd BufWritePre  * set noreadonly:autocmd BufWritePost * set readonly::try:  write /i/m/p/o/s/s/i/b/l/e:catch:  doautocmd BufWritePost /i/m/p/o/s/s/i/b/l/e:endtry

You can also use ":silent!":

:let x = "ok":let v:errmsg = "":autocmd BufWritePost * if v:errmsg != "":autocmd BufWritePost *   let x = "after fail":autocmd BufWritePost * endif:try:  silent! write /i/m/p/o/s/s/i/b/l/e:catch:endtry:echo x

This displays "after fail".

If the main action of the command does not fail, exceptions from theautocommands will be catchable by the caller of the command:

:autocmd BufWritePost * throw ":-(":autocmd BufWritePost * echo "Should not be displayed"::try:  write:catch:  echo v:exception:endtry

except-autocmd-Cmd
For some commands, the normal action can be replaced by a sequence ofautocommands. Exceptions from that sequence will be catchable by the callerof the command. Example: For the ":write" command, the caller cannot know whether the filehad actually been written when the exception occurred. You need to tell it insome way.

:if !exists("cnt"):  let cnt = 0::  autocmd BufWriteCmd * if &modified:  autocmd BufWriteCmd *   let cnt = cnt + 1:  autocmd BufWriteCmd *   if cnt % 3 == 2:  autocmd BufWriteCmd *     throw "BufWriteCmdError":  autocmd BufWriteCmd *   endif:  autocmd BufWriteCmd *   write | set nomodified:  autocmd BufWriteCmd *   if cnt % 3 == 0:  autocmd BufWriteCmd *     throw "BufWriteCmdError":  autocmd BufWriteCmd *   endif:  autocmd BufWriteCmd *   echo "File successfully written!":  autocmd BufWriteCmd * endif:endif::try:write:catch /^BufWriteCmdError$/:  if &modified:    echo "Error on writing (file contents not changed)":  else:    echo "Error after writing":  endif:catch /^Vim(write):/:    echo "Error on writing":endtry

When this script is sourced several times after making changes, it displaysfirst

File successfully written!

then

Error on writing (file contents not changed)

then

Error after writing

etc.

except-autocmd-ill
You cannot spread a try conditional over autocommands for different events.The following code is ill-formed:

:autocmd BufWritePre  * try::autocmd BufWritePost * catch:autocmd BufWritePost *   echo v:exception:autocmd BufWritePost * endtry::write

EXCEPTION HIERARCHIES AND PARAMETERIZED EXCEPTIONSexcept-hier-param

Some programming languages allow to use hierarchies of exception classes or topass additional information with the object of an exception class. You can dosimilar things in Vim. In order to throw an exception from a hierarchy, just throw the completeclass name with the components separated by a colon, for instance throw thestring "EXCEPT:MATHERR:OVERFLOW" for an overflow in a mathematical library. When you want to pass additional information with your exception class, addit in parentheses, for instance throw the string "EXCEPT:IO:WRITEERR(myfile)"for an error when writing "myfile". With the appropriate patterns in the ":catch" command, you can catch forbase classes or derived classes of your hierarchy. Additional information inparentheses can be cut out fromv:exception with the ":substitute" command. Example:

:function! CheckRange(a, func):  if a:a < 0:    throw "EXCEPT:MATHERR:RANGE(" .. a:func .. ")":  endif:endfunction::function! Add(a, b):  call CheckRange(a:a, "Add"):  call CheckRange(a:b, "Add"):  let c = a:a + a:b:  if c < 0:    throw "EXCEPT:MATHERR:OVERFLOW":  endif:  return c:endfunction::function! Div(a, b):  call CheckRange(a:a, "Div"):  call CheckRange(a:b, "Div"):  if (a:b == 0):    throw "EXCEPT:MATHERR:ZERODIV":  endif:  return a:a / a:b:endfunction::function! Write(file):  try:    execute "write" fnameescape(a:file):  catch /^Vim(write):/:    throw "EXCEPT:IO(" .. getcwd() .. ", " .. a:file .. "):WRITEERR":  endtry:endfunction::try::  " something with arithmetic and I/O::catch /^EXCEPT:MATHERR:RANGE/:  let function = substitute(v:exception, '.*(\(\a\+\)).*', '\1', ""):  echo "Range error in" function::catch /^EXCEPT:MATHERR/" catches OVERFLOW and ZERODIV:  echo "Math error"::catch /^EXCEPT:IO/:  let dir = substitute(v:exception, '.*(\(.\+\),\s*.\+).*', '\1', ""):  let file = substitute(v:exception, '.*(.\+,\s*\(.\+\)).*', '\1', ""):  if file !~ '^/':    let file = dir .. "/" .. file:  endif:  echo 'I/O error for "' .. file .. '"'::catch /^EXCEPT/:  echo "Unspecified error"::endtry

The exceptions raised by Vim itself (on error or when pressingCTRL-C) usea flat hierarchy: they are all in the "Vim" class. You cannot throw yourselfexceptions with the "Vim" prefix; they are reserved for Vim. Vim error exceptions are parameterized with the name of the command thatfailed, if known. Seecatch-errors.

PECULIARITIES

except-compat
The exception handling concept requires that the command sequence causing theexception is aborted immediately and control is transferred to finally clausesand/or a catch clause.

In the Vim script language there are cases where scripts and functionscontinue after an error: in functions without the "abort" flag or in a commandafter ":silent!", control flow goes to the following line, and outsidefunctions, control flow goes to the line following the outermost ":endwhile"or ":endif". On the other hand, errors should be catchable as exceptions(thus, requiring the immediate abortion).

This problem has been solved by converting errors to exceptions and usingimmediate abortion (if not suppressed by ":silent!") only when a tryconditional is active. This is no restriction since an (error) exception canbe caught only from an active try conditional. If you want an immediatetermination without catching the error, just use a try conditional withoutcatch clause. (You can cause cleanup code being executed before terminationby specifying a finally clause.)

When no try conditional is active, the usual abortion and continuationbehavior is used instead of immediate abortion. This ensures compatibility ofscripts written for Vim 6.1 and earlier.

However, when sourcing an existing script that does not use exception handlingcommands (or when calling one of its functions) from inside an active tryconditional of a new script, you might change the control flow of the existingscript on error. You get the immediate abortion on error and can catch theerror in the new script. If however the sourced script suppresses errormessages by using the ":silent!" command (checking for errors by testingv:errmsg if appropriate), its execution path is not changed. The error isnot converted to an exception. (See:silent.) So the only remaining causewhere this happens is for scripts that don't care about errors and produceerror messages. You probably won't want to use such code from your newscripts.

except-syntax-err
Syntax errors in the exception handling commands are never caught by any ofthe ":catch" commands of the try conditional they belong to. Its finallyclauses, however, is executed. Example:

:try:  try:    throw 4711:  catch /\(/:    echo "in catch with syntax error":  catch:    echo "inner catch-all":  finally:    echo "inner finally":  endtry:catch:  echo 'outer catch-all caught "' .. v:exception .. '"':  finally:    echo "outer finally":endtry

This displays:

inner finallyouter catch-all caught "Vim(catch):E54: Unmatched \("outer finally

The original exception is discarded and an error exception is raised, instead.

except-single-line
The ":try", ":catch", ":finally", and ":endtry" commands can be put ona single line, but then syntax errors may make it difficult to recognize the"catch" line, thus you better avoid this. Example:

:try | unlet! foo # | catch | endtry

raises an error exception for the trailing characters after the ":unlet!"argument, but does not see the ":catch" and ":endtry" commands, so that theerror exception is discarded and the "E488: Trailing characters" message getsdisplayed.

except-several-errors
When several errors appear in a single command, the first error message isusually the most specific one and therefore converted to the error exception. Example:

echo novar

causes

E121: Undefined variable: novarE15: Invalid expression: novar

The value of the error exception inside try conditionals is:

Vim(echo):E121: Undefined variable: novar

except-syntax-error
But when a syntax error is detected after a normal error in the same command,the syntax error is used for the exception being thrown. Example:

unlet novar #

causes

E108: No such variable: "novar"E488: Trailing characters

The value of the error exception inside try conditionals is:

Vim(unlet):E488: Trailing characters

This is done because the syntax error might change the execution path in a waynot intended by the user. Example:

try    try | unlet novar # | catch | echo v:exception | endtrycatch /.*/    echo "outer catch:" v:exceptionendtry

This displays "outer catch: Vim(unlet):E488: Trailing characters", and thena "E600: Missing :endtry" error message is given, seeexcept-single-line.

9. Exampleseval-examples

Printing in Binary

:" The function Nr2Bin() returns the binary string representation of a number.:func Nr2Bin(nr):  let n = a:nr:  let r = "":  while n:    let r = '01'[n % 2] .. r:    let n = n / 2:  endwhile:  return r:endfunc:" The function String2Bin() converts each character in a string to a:" binary string, separated with dashes.:func String2Bin(str):  let out = '':  for ix in range(strlen(a:str)):    let out = out .. '-' .. Nr2Bin(char2nr(a:str[ix])):  endfor:  return out[1:]:endfunc

Example of its use:

:echo Nr2Bin(32)

result: "100000"

:echo String2Bin("32")

result: "110011-110010"

Sorting lines

This example sorts lines with a specific compare function.

:func SortBuffer():  let lines = getline(1, '$'):  call sort(lines, function("Strcmp")):  call setline(1, lines):endfunction

As a one-liner:

:call setline(1, sort(getline(1, '$'), function("Strcmp")))

scanf() replacement

sscanf
There is no sscanf() function in Vim. If you need to extract parts from aline, you can use matchstr() and substitute() to do it. This example showshow to get the file name, line number and column number out of a line like"foobar.txt, 123, 45".

:" Set up the match bit:let mx='\(\f\+\),\s*\(\d\+\),\s*\(\d\+\)':"get the part matching the whole expression:let l = matchstr(line, mx):"get each item out of the match:let file = substitute(l, mx, '\1', ''):let lnum = substitute(l, mx, '\2', ''):let col = substitute(l, mx, '\3', '')

The input is in the variable "line", the results in the variables "file","lnum" and "col". (idea from Michael Geddes)

getting the scriptnames in a Dictionary

scriptnames-dictionary
The:scriptnames command can be used to get a list of all script files thathave been sourced. There is also thegetscriptinfo() function, but theinformation returned is not exactly the same. In case you need to manipulatethe output ofscriptnames this code can be used:

" Get the output of ":scriptnames" in the scriptnames_output variable.let scriptnames_output = ''redir => scriptnames_outputsilent scriptnamesredir END" Split the output into lines and parse each line.Add an entry to the" "scripts" dictionary.let scripts = {}for line in split(scriptnames_output, "\n")  " Only do non-blank lines.  if line =~ '\S'    " Get the first number in the line.    let nr = matchstr(line, '\d\+')    " Get the file name, remove the script number " 123: ".    let name = substitute(line, '.\+:\s*', '', '')    " Add an item to the Dictionary    let scripts[nr] = name  endifendforunlet scriptnames_output

The sandboxeval-sandboxsandbox

The'foldexpr','formatexpr','includeexpr','indentexpr','statusline' and'foldtext' options may be evaluated in a sandbox. This means that you areprotected from these expressions having nasty side effects. This gives somesafety for when these options are set from a modeline. It is also used whenthe command from a tags file is executed and forCTRL-R = in the command line.The sandbox is also used for the:sandbox command.

E48
These items are not allowed in the sandbox:

changing the buffer text

defining or changing mapping, autocommands, user commands

setting certain options (seeoption-summary)

setting certain v: variables (seev:var)E794

executing a shell command

reading or writing a file

jumping to another buffer or editing a file

executing Python, Perl, etc. commandsThis is not guaranteed 100% secure, but it should block most attacks.

:san:sandbox:san[dbox]{cmd}Execute{cmd} in the sandbox. Useful to evaluate anoption that may have been set from a modeline, e.g.'foldexpr'.

sandbox-option
A few options contain an expression. When this expression is evaluated it mayhave to be done in the sandbox to avoid a security risk. But the sandbox isrestrictive, thus this only happens when the option was set from an insecurelocation. Insecure in this context are:

sourcing a .nvimrc or .exrc in the current directory

while executing in the sandbox

value coming from a modeline

executing a function that was defined in the sandbox

Note that when in the sandbox and saving an option value and restoring it, theoption will still be marked as it was set in the sandbox.

Textlocktextlock

In a few situations it is not allowed to change the text in the buffer, jumpto another window and some other things that might confuse or break what Vimis currently doing. This mostly applies to things that happen when Vim isactually doing something else. For example, a TextYankPost autocommand cannotedit the text it is yanking.

This is not allowed when the textlock is active:

changing the buffer text

jumping to another buffer or window

editing another file

closing a window or quitting Vim

etc.

Vim script libraryvim-script-library

Vim comes bundled with a Vim script library, that can be used by runtime,script authors. Currently, it only includes very few functions, but it maygrow over time.

dist#vim
The functions make use of the autoloaded prefix "dist#vim".

The following functions are available:

dist#vim#IsSafeExecutable(filetype, executable)

This function takes a filetype and an executable and checks whether it is safeto execute the given executable. For security reasons users may not want tohave Vim execute random executables or may have forbidden to do so forspecific filetypes by setting the "<filetype>_exec" variable (plugin_exec).

It returnsTRUE orFALSE to indicate whether the plugin should run the givenexecutable. It takes the following arguments:

argumenttype

filetypestringexecutablestring

Command-line expressions highlightingexpr-highlight

Expressions entered by the user ini_CTRL-R_=,c_CTRL-\_e,quote= arehighlighted by the built-in expressions parser. It uses highlight groupsdescribed in the table below, which may be overridden by colorschemes.hl-NvimInvalid
Besides the "Nvim"-prefixed highlight groups described below, there are"NvimInvalid"-prefixed highlight groups which have the same meaning butindicate that the token contains an error or that an error occurred justbefore it. They have mostly the same hierarchy, except that (by default) inplace of any non-Nvim-prefixed group NvimInvalid linking toError is usedand some other intermediate groups are present.

Group Default link Colored expression

hl-NvimInternalError None, red/red Parser bug

hl-NvimAssignment Operator Generic assignmenthl-NvimPlainAssignment NvimAssignment= in:lethl-NvimAugmentedAssignment NvimAssignment Generic,+=/`-=`/`.=`hl-NvimAssignmentWithAddition NvimAugmentedAssignment+= in:let+=hl-NvimAssignmentWithSubtraction NvimAugmentedAssignment-= in:let-=hl-NvimAssignmentWithConcatenation NvimAugmentedAssignment.= in:let.=

hl-NvimOperator Operator Generic operator

hl-NvimUnaryOperator NvimOperator Generic unary ophl-NvimUnaryPlus NvimUnaryOperatorexpr-unary-+hl-NvimUnaryMinus NvimUnaryOperatorexpr-unary--hl-NvimNot NvimUnaryOperatorexpr-!

hl-NvimBinaryOperator NvimOperator Generic binary ophl-NvimComparison NvimBinaryOperator Anyexpr4 operatorhl-NvimComparisonModifier NvimComparison#/`?` nearexpr4 ophl-NvimBinaryPlus NvimBinaryOperatorexpr-+hl-NvimBinaryMinus NvimBinaryOperatorexpr--hl-NvimConcat NvimBinaryOperatorexpr-.hl-NvimConcatOrSubscript NvimConcatexpr-. orexpr-entryhl-NvimOr NvimBinaryOperatorexpr-barbarhl-NvimAnd NvimBinaryOperatorexpr-&&hl-NvimMultiplication NvimBinaryOperatorexpr-starhl-NvimDivision NvimBinaryOperatorexpr-/hl-NvimMod NvimBinaryOperatorexpr-%

hl-NvimTernary NvimOperator? inexpr1hl-NvimTernaryColon NvimTernary: inexpr1

hl-NvimParenthesis Delimiter Generic brackethl-NvimLambda NvimParenthesis{/`}` inlambdahl-NvimNestingParenthesis NvimParenthesis(/`)` inexpr-nestinghl-NvimCallingParenthesis NvimParenthesis(/`)` inexpr-function

hl-NvimSubscript NvimParenthesis Generic subscripthl-NvimSubscriptBracket NvimSubscript[/`]` inexpr-[]hl-NvimSubscriptColon NvimSubscript: inexpr-[:]hl-NvimCurly NvimSubscript{/`}` incurly-braces-names

hl-NvimContainer NvimParenthesis Generic containerhl-NvimDict NvimContainer{/`}` indict literalhl-NvimList NvimContainer[/`]` inlist literal

hl-NvimIdentifier Identifier Generic identifierhl-NvimIdentifierScope NvimIdentifier Namespace: letter before: ininternal-variableshl-NvimIdentifierScopeDelimiter NvimIdentifier: after namespace letterhl-NvimIdentifierName NvimIdentifier Rest of the identhl-NvimIdentifierKey NvimIdentifier Identifier afterexpr-entry

hl-NvimColon Delimiter: indict literalhl-NvimComma Delimiter, indict orlist literal orexpr-functionhl-NvimArrow Delimiter-> inlambda

hl-NvimRegister SpecialCharexpr-registerhl-NvimNumber Number Non-prefix digits in integerexpr-numberhl-NvimNumberPrefix Type0 foroctal-number0x forhex-number0b forbinary-numberhl-NvimFloat NvimNumber Floating-point number

hl-NvimOptionSigil Type& inexpr-optionhl-NvimOptionScope NvimIdentifierScope Option scope if anyhl-NvimOptionScopeDelimiter NvimIdentifierScopeDelimiter: after option scopehl-NvimOptionName NvimIdentifier Option name

hl-NvimEnvironmentSigil NvimOptionSigil$ inexpr-envhl-NvimEnvironmentName NvimIdentifier Env variable name

hl-NvimString String Generic stringhl-NvimStringBody NvimString Generic string literal bodyhl-NvimStringQuote NvimString Generic string quotehl-NvimStringSpecial SpecialChar Generic string non-literal body

hl-NvimSingleQuote NvimStringQuote' inexpr-'hl-NvimSingleQuotedBody NvimStringBody Literal part ofexpr-' string bodyhl-NvimSingleQuotedQuote NvimStringSpecial'' insideexpr-' string body

hl-NvimDoubleQuote NvimStringQuote" inexpr-quotehl-NvimDoubleQuotedBody NvimStringBody Literal part ofexpr-quote bodyhl-NvimDoubleQuotedEscape NvimStringSpecial Validexpr-quote escape sequencehl-NvimDoubleQuotedUnknownEscape NvimInvalidValue Unrecognizedexpr-quote escape sequence

5. Defining functions

6. Curly braces names

7. Commands

8. Exception handling

9. Examples