$PATHEXT to try using the name
		without an extension.  When 'shell' looks like a Unix shell,
		then the name is also tried without adding an extension.
		On MS-Windows it only checks if the file exists and is not a
		directory, not if it's really executable.
		On MS-Windows an executable in the same directory as the Vim
		executable is always found (it's added to $PATH at |startup|).
					*NoDefaultCurrentDirectoryInExePath*
		On MS-Windows an executable in Vim's current working directory
		is also normally found, but this can be disabled by setting
		the $NoDefaultCurrentDirectoryInExePath environment variable.

		The result is a Number:
			1	exists
			0	does not exist
		|exepath()| can be used to get the full path of an executable.

                Parameters: ~
                  • {expr} (`string`)

                Return: ~
                  (`0|1`)

execute({command} [, {silent}])                                      *execute()*
		Execute {command} and capture its output.
		If {command} is a |String|, returns {command} output.
		If {command} is a |List|, returns concatenated outputs.
		Line continuations in {command} are not recognized.
		Examples: >vim
			echo execute('echon "foo"')
<			foo >vim
			echo execute(['echon "foo"', 'echon "bar"'])
<			foobar

		The optional {silent} argument can have these values:
			""		no `:silent` used
			"silent"	`:silent` used
			"silent!"	`:silent!` used
		The default is "silent".  Note that with "silent!", unlike
		`:redir`, error messages are dropped.

		To get a list of lines use `split()` on the result: >vim
			execute('args')->split("\n")

<		This function is not available in the |sandbox|.
		Note: If nested, an outer execute() will not observe output of
		the inner calls.
		Note: Text attributes (highlights) are not captured.
		To execute a command in another window than the current one
		use `win_execute()`.

                Parameters: ~
                  • {command} (`string|string[]`)
                  • {silent} (`''|'silent'|'silent!'?`)

                Return: ~
                  (`string`)

exepath({expr})                                                      *exepath()*
		Returns the full path of {expr} if it is an executable and
		given as a (partial or full) path or is found in $PATH.
		Returns empty string otherwise.
		If {expr} starts with "./" the |current-directory| is used.

                Parameters: ~
                  • {expr} (`string`)

                Return: ~
                  (`string`)

exists({expr})                                                        *exists()*
		The result is a Number, which is |TRUE| if {expr} is
		defined, zero otherwise.

		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|
					entries, |List| items, etc.
					Beware that evaluating an index may
					cause an error message for an invalid
					expression.  E.g.: >vim
					   let l = [1, 2, 3]
					   echo exists("l[5]")
<					   0 >vim
					   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-function|). Also works for a
					variable that is a Funcref.
			: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|