import { exists } from "https://deno.land/x/denops_std@v5.0.2/function/common.ts";
The result is a Number, which is TRUE
if {expr} is defined,
zero otherwise.
Note: In a compiled :def
function the evaluation is done at
runtime. Use exists_compiled()
to evaluate the expression
at compile time.
For checking for a supported feature use has()
.
For checking if a file exists use filereadable()
.
The {expr} argument is a string, which contains one of these:
varname internal variable (see
dict.key internal-variables
). Also works
list[i] for curly-braces-names
, Dictionary
import.Func entries, List
items, imported
items, etc.
Does not work for local variables in a
compiled :def
function.
Also works for a function in Vim9
script, since it can be used as a
function reference.
Beware that evaluating an index may
cause an error message for an invalid
expression. E.g.:
:let l = [1, 2, 3]
:echo exists("l[5]")
0
:echo exists("l[xx]")
E121: Undefined variable: xx
0
&option-name Vim option (only checks if it exists,
not if it really works)
+option-name Vim option that works.
$ENVNAME environment variable (could also be
done by comparing with an empty
string)
*funcname built-in function (see `functions`)
or user defined function (see
`user-functions`) that is implemented.
Also works for a variable that is a
Funcref.
?funcname built-in function that could be
implemented; to be used to check if
"funcname" is valid
:cmdname Ex command: built-in command, user
command or command modifier `:command`.
Returns:
1 for match with start of a command
2 full match with a command
3 matches several user commands
To check for a supported command
always check the return value to be 2.
:2match The `:2match` command.
:3match The `:3match` command (but you
probably should not use it, it is
reserved for internal usage)
`#event` autocommand defined for this event
`#event#pattern` autocommand defined for this event and
pattern (the pattern is taken
literally and compared to the
autocommand patterns character by
character)
`#group` autocommand group exists
`#group#event` autocommand defined for this group and
event.
`#group#event#pattern`
autocommand defined for this group,
event and pattern.
`##event` autocommand for this event is
supported.
Examples:
exists("&shortname")
exists("$HOSTNAME")
exists("*strftime")
exists("*s:MyFunc") " only for legacy script
exists("*MyFunc")
exists("bufcount")
exists(":Make")
exists("#CursorHold")
exists("#BufReadPre#*.gz")
exists("#filetypeindent")
exists("#filetypeindent#FileType")
exists("#filetypeindent#FileType#*")
exists("##ColorScheme")
There must be no space between the symbol (&/$/* /#) and the name. There must be no extra characters after the name, although in a few cases this is ignored. That may become stricter in the future, thus don't count on it! Working example:
exists(":make")
NOT working example:
exists(":make install")
Note that the argument must be a string, not the name of the variable itself. For example:
exists(bufcount)
This doesn't check for existence of the "bufcount" variable, but gets the value of "bufcount", and checks if that exists.
Can also be used as a method
:
Varname()->exists()