# Vim documentation: pattern

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    *pattern.txt*   For Vim version 8.2.  Last change: 2021 Jul 16

    		  VIM REFERENCE MANUAL    by Bram Moolenaar

    Patterns and search commands				*pattern-searches*

    The very basics can be found in section |03.9| of the user manual.  A few more
    explanations are in chapter 27 |usr_27.txt|.

    1. Search commands		|search-commands|
    2. The definition of a pattern	|search-pattern|
    3. Magic			|/magic|
    4. Overview of pattern items	|pattern-overview|
    5. Multi items			|pattern-multi-items|
    6. Ordinary atoms		|pattern-atoms|
    7. Ignoring case in a pattern	|/ignorecase|
    8. Composing characters		|patterns-composing|
    9. Compare with Perl patterns	|perl-patterns|
    10. Highlighting matches	|match-highlight|
    11. Fuzzy matching		|fuzzy-match|

    ==============================================================================

    1. Search commands				*search-commands*

    							*/*
    /{pattern}[/]<CR>	Search forward for the [count]'th occurrence of
    			{pattern} |exclusive|.

    /{pattern}/{offset}<CR>	Search forward for the [count]'th occurrence of
    			{pattern} and go |{offset}| lines up or down.
    			|linewise|.

    							*/<CR>*
    /<CR>			Search forward for the [count]'th occurrence of the
    			latest used pattern |last-pattern| with latest used
    			|{offset}|.

    //{offset}<CR>		Search forward for the [count]'th occurrence of the
    			latest used pattern |last-pattern| with new
    			|{offset}|.  If {offset} is empty no offset is used.

    							*?*
    ?{pattern}[?]<CR>	Search backward for the [count]'th previous
    			occurrence of {pattern} |exclusive|.

    ?{pattern}?{offset}<CR>	Search backward for the [count]'th previous
    			occurrence of {pattern} and go |{offset}| lines up or
    			down |linewise|.

    							*?<CR>*
    ?<CR>			Search backward for the [count]'th occurrence of the
    			latest used pattern |last-pattern| with latest used
    			|{offset}|.

    ??{offset}<CR>		Search backward for the [count]'th occurrence of the
    			latest used pattern |last-pattern| with new
    			|{offset}|.  If {offset} is empty no offset is used.

    							*n*
    n			Repeat the latest "/" or "?" [count] times.
    			If the cursor doesn't move the search is repeated with
    			count + 1.
    			|last-pattern|

    							*N*
    N			Repeat the latest "/" or "?" [count] times in
    			opposite direction. |last-pattern|

    							*star* *E348* *E349*
    *			Search forward for the [count]'th occurrence of the
    			word nearest to the cursor.  The word used for the
    			search is the first of:
    				1. the keyword under the cursor |'iskeyword'|
    				2. the first keyword after the cursor, in the
    				   current line
    				3. the non-blank word under the cursor
    				4. the first non-blank word after the cursor,
    				   in the current line
    			Only whole keywords are searched for, like with the
    			command "/\<keyword\>".  |exclusive|
    			'ignorecase' is used, 'smartcase' is not.

    							*#*
    #			Same as "*", but search backward.  The pound sign
    			(character 163) also works.  If the "#" key works as
    			backspace, try using "stty erase <BS>" before starting
    			Vim (<BS> is CTRL-H or a real backspace).

    							*gstar*
    g*			Like "*", but don't put "\<" and "\>" around the word.
    			This makes the search also find matches that are not a
    			whole word.

    							*g#*
    g#			Like "#", but don't put "\<" and "\>" around the word.
    			This makes the search also find matches that are not a
    			whole word.

    							*gd*
    gd			Goto local Declaration.  When the cursor is on a local
    			variable, this command will jump to its declaration.
    			First Vim searches for the start of the current
    			function, just like "[[".  If it is not found the
    			search stops in line 1.  If it is found, Vim goes back
    			until a blank line is found.  From this position Vim
    			searches for the keyword under the cursor, like with
    			"*", but lines that look like a comment are ignored
    			(see 'comments' option).
    			Note that this is not guaranteed to work, Vim does not
    			really check the syntax, it only searches for a match
    			with the keyword.  If included files also need to be
    			searched use the commands listed in |include-search|.
    			After this command |n| searches forward for the next
    			match (not backward).

    							*gD*
    gD			Goto global Declaration.  When the cursor is on a
    			global variable that is defined in the file, this
    			command will jump to its declaration.  This works just
    			like "gd", except that the search for the keyword
    			always starts in line 1.

    							*1gd*
    1gd			Like "gd", but ignore matches inside a {} block that
    			ends before the cursor position.

    							*1gD*
    1gD			Like "gD", but ignore matches inside a {} block that
    			ends before the cursor position.

    							*CTRL-C*
    CTRL-C			Interrupt current (search) command.  Use CTRL-Break on
    			MS-Windows |dos-CTRL-Break|.
    			In Normal mode, any pending command is aborted.

    							*:noh* *:nohlsearch*
    :noh[lsearch]		Stop the highlighting for the 'hlsearch' option.  It
    			is automatically turned back on when using a search
    			command, or setting the 'hlsearch' option.
    			This command doesn't work in an autocommand, because
    			the highlighting state is saved and restored when
    			executing autocommands |autocmd-searchpat|.
    			Same thing for when invoking a user function.

    While typing the search pattern the current match will be shown if the
    'incsearch' option is on.  Remember that you still have to finish the search
    command with <CR> to actually position the cursor at the displayed match.  Or
    use <Esc> to abandon the search.

    All matches for the last used search pattern will be highlighted if you set
    the 'hlsearch' option.  This can be suspended with the |:nohlsearch| command.

    When 'shortmess' does not include the "S" flag, Vim will automatically show an
    index, on which the cursor is. This can look like this:

      [1/5]		Cursor is on first of 5 matches.
      [1/>99]	Cursor is on first of more than 99 matches.
      [>99/>99]	Cursor is after 99 match of more than 99 matches.
      [?/??]	Unknown how many matches exists, generating the
    		statistics was aborted because of search timeout.

    Note: the count does not take offset into account.

    When no match is found you get the error: *E486* Pattern not found
    Note that for the |:global| command this behaves like a normal message, for Vi
    compatibility.  For the |:s| command the "e" flag can be used to avoid the
    error message |:s_flags|.

    					*search-offset* *{offset}*
    These commands search for the specified pattern.  With "/" and "?" an
    additional offset may be given.  There are two types of offsets: line offsets
    and character offsets.

    The offset gives the cursor position relative to the found match:
        [num]	[num] lines downwards, in column 1
        +[num]	[num] lines downwards, in column 1
        -[num]	[num] lines upwards, in column 1
        e[+num]	[num] characters to the right of the end of the match
        e[-num]	[num] characters to the left of the end of the match
        s[+num]	[num] characters to the right of the start of the match
        s[-num]	[num] characters to the left of the start of the match
        b[+num]	[num] identical to s[+num] above (mnemonic: begin)
        b[-num]	[num] identical to s[-num] above (mnemonic: begin)
        ;{pattern}  perform another search, see |//;|

    If a '-' or '+' is given but [num] is omitted, a count of one will be used.
    When including an offset with 'e', the search becomes inclusive (the
    character the cursor lands on is included in operations).

    Examples:

    pattern			cursor position
    /test/+1		one line below "test", in column 1
    /test/e			on the last t of "test"
    /test/s+2		on the 's' of "test"
    /test/b-3		three characters before "test"

    If one of these commands is used after an operator, the characters between
    the cursor position before and after the search is affected.  However, if a
    line offset is given, the whole lines between the two cursor positions are
    affected.

    An example of how to search for matches with a pattern and change the match
    with another word:
    	/foo<CR>	find "foo"
    	c//e<CR>	change until end of match
    	bar<Esc>	type replacement
    	//<CR>		go to start of next match
    	c//e<CR>	change until end of match
    	beep<Esc>	type another replacement
    			etc.

    							*//;* *E386*
    A very special offset is ';' followed by another search command.  For example:

       /test 1/;/test
       /test.*/+1;?ing?

    The first one first finds the next occurrence of "test 1", and then the first
    occurrence of "test" after that.

    This is like executing two search commands after each other, except that:
    - It can be used as a single motion command after an operator.
    - The direction for a following "n" or "N" command comes from the first
      search command.
    - When an error occurs the cursor is not moved at all.

    							*last-pattern*
    The last used pattern and offset are remembered.  They can be used to repeat
    the search, possibly in another direction or with another count.  Note that
    two patterns are remembered: One for "normal" search commands and one for the
    substitute command ":s".  Each time an empty pattern is given, the previously
    used pattern is used.  However, if there is no previous search command, a
    previous substitute pattern is used, if possible.

    The 'magic' option sticks with the last used pattern.  If you change 'magic',
    this will not change how the last used pattern will be interpreted.
    The 'ignorecase' option does not do this.  When 'ignorecase' is changed, it
    will result in the pattern to match other text.

    All matches for the last used search pattern will be highlighted if you set
    the 'hlsearch' option.

    To clear the last used search pattern:
    	:let @/ = ""
    This will not set the pattern to an empty string, because that would match
    everywhere.  The pattern is really cleared, like when starting Vim.

    The search usually skips matches that don't move the cursor.  Whether the next
    match is found at the next character or after the skipped match depends on the
    'c' flag in 'cpoptions'.  See |cpo-c|.
    	   with 'c' flag:   "/..." advances 1 to 3 characters
    	without 'c' flag:   "/..." advances 1 character
    The unpredictability with the 'c' flag is caused by starting the search in the
    first column, skipping matches until one is found past the cursor position.

    When searching backwards, searching starts at the start of the line, using the
    'c' flag in 'cpoptions' as described above.  Then the last match before the
    cursor position is used.

    In Vi the ":tag" command sets the last search pattern when the tag is searched
    for.  In Vim this is not done, the previous search pattern is still remembered,
    unless the 't' flag is present in 'cpoptions'.  The search pattern is always
    put in the search history.

    If the 'wrapscan' option is on (which is the default), searches wrap around
    the end of the buffer.  If 'wrapscan' is not set, the backward search stops
    at the beginning and the forward search stops at the end of the buffer.  If
    'wrapscan' is set and the pattern was not found the error message "pattern
    not found" is given, and the cursor will not be moved.  If 'wrapscan' is not
    set the message becomes "search hit BOTTOM without match" when searching
    forward, or "search hit TOP without match" when searching backward.  If
    wrapscan is set and the search wraps around the end of the file the message
    "search hit TOP, continuing at BOTTOM" or "search hit BOTTOM, continuing at
    TOP" is given when searching backwards or forwards respectively.  This can be
    switched off by setting the 's' flag in the 'shortmess' option.  The highlight
    method 'w' is used for this message (default: standout).

    							*search-range*
    You can limit the search command "/" to a certain range of lines by including
    \%>l items.  For example, to match the word "limit" below line 199 and above
    line 300:
    	/\%>199l\%<300llimit
    Also see |/\%>l|.

    Another way is to use the ":substitute" command with the 'c' flag.  Example:
       :.,300s/Pattern//gc
    This command will search from the cursor position until line 300 for
    "Pattern".  At the match, you will be asked to type a character.  Type 'q' to
    stop at this match, type 'n' to find the next match.

    The "*", "#", "g*" and "g#" commands look for a word near the cursor in this
    order, the first one that is found is used:
    - The keyword currently under the cursor.
    - The first keyword to the right of the cursor, in the same line.
    - The WORD currently under the cursor.
    - The first WORD to the right of the cursor, in the same line.
    The keyword may only contain letters and characters in 'iskeyword'.
    The WORD may contain any non-blanks (<Tab>s and/or <Space>s).
    Note that if you type with ten fingers, the characters are easy to remember:
    the "#" is under your left hand middle finger (search to the left and up) and
    the "*" is under your right hand middle finger (search to the right and down).
    (this depends on your keyboard layout though).

    								*E956*
    In very rare cases a regular expression is used recursively.  This can happen
    when executing a pattern takes a long time and when checking for messages on
    channels a callback is invoked that also uses a pattern or an autocommand is
    triggered.  In most cases this should be fine, but if a pattern is in use when
    it's used again it fails.  Usually this means there is something wrong with
    the pattern.

    ==============================================================================

    2. The definition of a pattern		*search-pattern* *pattern* *[pattern]*

    					*regular-expression* *regexp* *Pattern*

    					*E76* *E383* *E476*

    For starters, read chapter 27 of the user manual |usr_27.txt|.

    						*/bar* */\bar* */pattern*
    1. A pattern is one or more branches, separated by "\|".  It matches anything
       that matches one of the branches.  Example: "foo\|beep" matches "foo" and
       matches "beep".  If more than one branch matches, the first one is used.

       pattern ::=	    branch
    		or  branch \| branch
    		or  branch \| branch \| branch
    		etc.

    						*/branch* */\&*
    2. A branch is one or more concats, separated by "\&".  It matches the last
       concat, but only if all the preceding concats also match at the same
       position.  Examples:
    	"foobeep\&..." matches "foo" in "foobeep".
    	".*Peter\&.*Bob" matches in a line containing both "Peter" and "Bob"

       branch ::=	    concat
    		or  concat \& concat
    		or  concat \& concat \& concat
    		etc.

    						*/concat*
    3. A concat is one or more pieces, concatenated.  It matches a match for the
       first piece, followed by a match for the second piece, etc.  Example:
       "f[0-9]b", first matches "f", then a digit and then "b".

       concat  ::=	    piece
    		or  piece piece
    		or  piece piece piece
    		etc.

    						*/piece*
    4. A piece is an atom, possibly followed by a multi, an indication of how many
       times the atom can be matched.  Example: "a*" matches any sequence of "a"
       characters: "", "a", "aa", etc.  See |/multi|.

       piece   ::=	    atom
    		or  atom  multi

    						*/atom*
    5. An atom can be one of a long list of items.  Many atoms match one character
       in the text.  It is often an ordinary character or a character class.
       Parentheses can be used to make a pattern into an atom.  The "\z(\)"
       construct is only for syntax highlighting.

       atom    ::=	    ordinary-atom		|/ordinary-atom|
    		or  \( pattern \)		|/\(|
    		or  \%( pattern \)		|/\%(|
    		or  \z( pattern \)		|/\z(|

    				*/\%#=* *two-engines* *NFA*
    Vim includes two regexp engines:
    1. An old, backtracking engine that supports everything.
    2. A new, NFA engine that works much faster on some patterns, possibly slower
       on some patterns.

    Vim will automatically select the right engine for you.  However, if you run
    into a problem or want to specifically select one engine or the other, you can
    prepend one of the following to the pattern:

    	\%#=0	Force automatic selection.  Only has an effect when
    	        'regexpengine' has been set to a non-zero value.
    	\%#=1	Force using the old engine.
    	\%#=2	Force using the NFA engine.

    You can also use the 'regexpengine' option to change the default.

    			 *E864* *E868* *E874* *E875* *E876* *E877* *E878*
    If selecting the NFA engine and it runs into something that is not implemented
    the pattern will not match.  This is only useful when debugging Vim.

    ==============================================================================

    3. Magic							*/magic*

    Some characters in the pattern, such as letters, are taken literally.  They
    match exactly the same character in the text.  When preceded with a backslash
    however, these characters may get a special meaning.  For example, "a" matches
    the letter "a", while "\a" matches any alphabetic character.

    Other characters have a special meaning without a backslash.  They need to be
    preceded with a backslash to match literally.  For example "." matches any
    character while "\." matches a dot.

    If a character is taken literally or not depends on the 'magic' option and the
    items in the pattern mentioned next.  The 'magic' option should always be set,
    but it can be switched off for Vi compatibility.  We mention the effect of
    'nomagic' here for completeness, but we recommend against using that.

    							*/\m* */\M*
    Use of "\m" makes the pattern after it be interpreted as if 'magic' is set,
    ignoring the actual value of the 'magic' option.
    Use of "\M" makes the pattern after it be interpreted as if 'nomagic' is used.

    							*/\v* */\V*
    Use of "\v" means that after it, all ASCII characters except '0'-'9', 'a'-'z',
    'A'-'Z' and '_' have special meaning: "very magic"

    Use of "\V" means that after it, only a backslash and the terminating
    character (usually / or ?) have special meaning: "very nomagic"

    Examples:
    after:	  \v	   \m	    \M	     \V		matches
    		'magic' 'nomagic'
    	  a	   a	    a	     a		literal 'a'
    	  \a	   \a	    \a	     \a		any alphabetic character
    	  .	   .	    \.	     \.		any character
    	  \.	   \.	    .	     .		literal dot
    	  $	   $	    $	     \$		end-of-line
    	  *	   *	    \*	     \*		any number of the previous atom
    	  ~	   ~	    \~	     \~		latest substitute string
    	  ()	   \(\)     \(\)     \(\)	group as an atom
    	  |	   \|	    \|	     \|		nothing: separates alternatives
    	  \\	   \\	    \\	     \\		literal backslash
    	  \{	   {	    {	     {		literal curly brace

    {only Vim supports \m, \M, \v and \V}

    If you want to you can make a pattern immune to the 'magic' option being set
    or not by putting "\m" or "\M" at the start of the pattern.

    ==============================================================================

    4. Overview of pattern items				*pattern-overview*

    						*E865* *E866* *E867* *E869*

    Overview of multi items.				*/multi* *E61* *E62*

    More explanation and examples below, follow the links.		*E64* *E871*

    	  multi
         'magic' 'nomagic'	matches of the preceding atom
    |/star|	*	\*	0 or more	as many as possible
    |/\+|	\+	\+	1 or more	as many as possible
    |/\=|	\=	\=	0 or 1		as many as possible
    |/\?|	\?	\?	0 or 1		as many as possible

    |/\{|	\{n,m}	\{n,m}	n to m		as many as possible
    	\{n}	\{n}	n		exactly
    	\{n,}	\{n,}	at least n	as many as possible
    	\{,m}	\{,m}	0 to m		as many as possible
    	\{}	\{}	0 or more	as many as possible (same as *)

    |/\{-|	\{-n,m}	\{-n,m}	n to m		as few as possible
    	\{-n}	\{-n}	n		exactly
    	\{-n,}	\{-n,}	at least n	as few as possible
    	\{-,m}	\{-,m}	0 to m		as few as possible
    	\{-}	\{-}	0 or more	as few as possible

    							*E59*
    |/\@>|	\@>	\@>	1, like matching a whole pattern
    |/\@=|	\@=	\@=	nothing, requires a match |/zero-width|
    |/\@!|	\@!	\@!	nothing, requires NO match |/zero-width|
    |/\@<=|	\@<=	\@<=	nothing, requires a match behind |/zero-width|
    |/\@<!|	\@<!	\@<!	nothing, requires NO match behind |/zero-width|

    Overview of ordinary atoms.				*/ordinary-atom*
    More explanation and examples below, follow the links.

          ordinary atom
          magic   nomagic	matches
    |/^|	^	^	start-of-line (at start of pattern) |/zero-width|
    |/\^|	\^	\^	literal '^'
    |/\_^|	\_^	\_^	start-of-line (used anywhere) |/zero-width|
    |/$|	$	$	end-of-line (at end of pattern) |/zero-width|
    |/\$|	\$	\$	literal '$'
    |/\_$|	\_$	\_$	end-of-line (used anywhere) |/zero-width|
    |/.|	.	\.	any single character (not an end-of-line)
    |/\_.|	\_.	\_.	any single character or end-of-line
    |/\<|	\<	\<	beginning of a word |/zero-width|
    |/\>|	\>	\>	end of a word |/zero-width|
    |/\zs|	\zs	\zs	anything, sets start of match
    |/\ze|	\ze	\ze	anything, sets end of match

    |/\%^|	\%^	\%^	beginning of file |/zero-width|		*E71*
    |/\%$|	\%$	\%$	end of file |/zero-width|
    |/\%V|	\%V	\%V	inside Visual area |/zero-width|
    |/\%#|	\%#	\%#	cursor position |/zero-width|
    |/\%'m|	\%'m	\%'m	mark m position |/zero-width|
    |/\%l|	\%23l	\%23l	in line 23 |/zero-width|
    |/\%c|	\%23c	\%23c	in column 23 |/zero-width|
    |/\%v|	\%23v	\%23v	in virtual column 23 |/zero-width|

    Character classes:					*/character-classes*
          magic   nomagic	matches
    |/\i|	\i	\i	identifier character (see 'isident' option)
    |/\I|	\I	\I	like "\i", but excluding digits
    |/\k|	\k	\k	keyword character (see 'iskeyword' option)
    |/\K|	\K	\K	like "\k", but excluding digits
    |/\f|	\f	\f	file name character (see 'isfname' option)
    |/\F|	\F	\F	like "\f", but excluding digits
    |/\p|	\p	\p	printable character (see 'isprint' option)
    |/\P|	\P	\P	like "\p", but excluding digits
    |/\s|	\s	\s	whitespace character: <Space> and <Tab>
    |/\S|	\S	\S	non-whitespace character; opposite of \s
    |/\d|	\d	\d	digit:				[0-9]
    |/\D|	\D	\D	non-digit:			[^0-9]
    |/\x|	\x	\x	hex digit:			[0-9A-Fa-f]
    |/\X|	\X	\X	non-hex digit:			[^0-9A-Fa-f]
    |/\o|	\o	\o	octal digit:			[0-7]
    |/\O|	\O	\O	non-octal digit:		[^0-7]
    |/\w|	\w	\w	word character:			[0-9A-Za-z_]
    |/\W|	\W	\W	non-word character:		[^0-9A-Za-z_]
    |/\h|	\h	\h	head of word character:		[A-Za-z_]
    |/\H|	\H	\H	non-head of word character:	[^A-Za-z_]
    |/\a|	\a	\a	alphabetic character:		[A-Za-z]
    |/\A|	\A	\A	non-alphabetic character:	[^A-Za-z]
    |/\l|	\l	\l	lowercase character:		[a-z]
    |/\L|	\L	\L	non-lowercase character:	[^a-z]
    |/\u|	\u	\u	uppercase character:		[A-Z]
    |/\U|	\U	\U	non-uppercase character		[^A-Z]
    |/\_|	\_x	\_x	where x is any of the characters above: character
    			class with end-of-line included
    (end of character classes)

          magic   nomagic	matches
    |/\e|	\e	\e	<Esc>
    |/\t|	\t	\t	<Tab>
    |/\r|	\r	\r	<CR>
    |/\b|	\b	\b	<BS>
    |/\n|	\n	\n	end-of-line
    |/~|	~	\~	last given substitute string
    |/\1|	\1	\1	same string as matched by first \(\)
    |/\2|	\2	\2	Like "\1", but uses second \(\)
    	   ...
    |/\9|	\9	\9	Like "\1", but uses ninth \(\)

    								*E68*
    |/\z1|	\z1	\z1	only for syntax highlighting, see |:syn-ext-match|
    	   ...
    |/\z1|	\z9	\z9	only for syntax highlighting, see |:syn-ext-match|

    	x	x	a character with no special meaning matches itself

    |/[]|	[]	\[]	any character specified inside the []
    |/\%[]|	\%[]	\%[]	a sequence of optionally matched atoms

    |/\c|	\c	\c	ignore case, do not use the 'ignorecase' option
    |/\C|	\C	\C	match case, do not use the 'ignorecase' option
    |/\Z|	\Z	\Z	ignore differences in Unicode "combining characters".
    			Useful when searching voweled Hebrew or Arabic text.

          magic   nomagic	matches
    |/\m|	\m	\m	'magic' on for the following chars in the pattern
    |/\M|	\M	\M	'magic' off for the following chars in the pattern
    |/\v|	\v	\v	the following chars in the pattern are "very magic"
    |/\V|	\V	\V	the following chars in the pattern are "very nomagic"
    |/\%#=|   \%#=1   \%#=1   select regexp engine |/zero-width|

    |/\%d|	\%d	\%d	match specified decimal character (eg \%d123)
    |/\%x|	\%x	\%x	match specified hex character (eg \%x2a)
    |/\%o|	\%o	\%o	match specified octal character (eg \%o040)
    |/\%u|	\%u	\%u	match specified multibyte character (eg \%u20ac)
    |/\%U|	\%U	\%U	match specified large multibyte character (eg
    			\%U12345678)
    |/\%C|	\%C	\%C	match any composing characters

    Example			matches
    \<\I\i*		or
    \<\h\w*
    \<[a-zA-Z_][a-zA-Z0-9_]*
    			An identifier (e.g., in a C program).

    \(\.$\|\. \)		A period followed by <EOL> or a space.

    [.!?][])"']*\($\|[ ]\)	A search pattern that finds the end of a sentence,
    			with almost the same definition as the ")" command.

    cat\Z			Both "cat" and "càt" ("a" followed by 0x0300)
    			Does not match "càt" (character 0x00e0), even
    			though it may look the same.

    ==============================================================================

    5. Multi items						*pattern-multi-items*

    An atom can be followed by an indication of how many times the atom can be
    matched and in what way.  This is called a multi.  See |/multi| for an
    overview.

    							*/star* */\star*
    *	(use \* when 'magic' is not set)
    	Matches 0 or more of the preceding atom, as many as possible.
    	Example  'nomagic'	matches
    	a*	   a\*		"", "a", "aa", "aaa", etc.
    	.*	   \.\*		anything, also an empty string, no end-of-line
    	\_.*	   \_.\*	everything up to the end of the buffer
    	\_.*END	   \_.\*END	everything up to and including the last "END"
    				in the buffer

    	Exception: When "*" is used at the start of the pattern or just after
    	"^" it matches the star character.

    	Be aware that repeating "\_." can match a lot of text and take a long
    	time.  For example, "\_.*END" matches all text from the current
    	position to the last occurrence of "END" in the file.  Since the "*"
    	will match as many as possible, this first skips over all lines until
    	the end of the file and then tries matching "END", backing up one
    	character at a time.

    							*/\+*
    \+	Matches 1 or more of the preceding atom, as many as possible.
    	Example		matches
    	^.\+$		any non-empty line
    	\s\+		white space of at least one character

    							*/\=*
    \=	Matches 0 or 1 of the preceding atom, as many as possible.
    	Example		matches
    	foo\=		"fo" and "foo"

    							*/\?*
    \?	Just like \=.  Cannot be used when searching backwards with the "?"
    	command.

    					*/\{* *E60* *E554* *E870*
    \{n,m}	Matches n to m of the preceding atom, as many as possible
    \{n}	Matches n of the preceding atom
    \{n,}	Matches at least n of the preceding atom, as many as possible
    \{,m}	Matches 0 to m of the preceding atom, as many as possible
    \{}	Matches 0 or more of the preceding atom, as many as possible (like *)

    							*/\{-*
    \{-n,m}	matches n to m of the preceding atom, as few as possible
    \{-n}	matches n of the preceding atom
    \{-n,}	matches at least n of the preceding atom, as few as possible
    \{-,m}	matches 0 to m of the preceding atom, as few as possible
    \{-}	matches 0 or more of the preceding atom, as few as possible

    	n and m are positive decimal numbers or zero

    								*non-greedy*
    	If a "-" appears immediately after the "{", then a shortest match
    	first algorithm is used (see example below).  In particular, "\{-}" is
    	the same as "*" but uses the shortest match first algorithm.  BUT: A
    	match that starts earlier is preferred over a shorter match: "a\{-}b"
    	matches "aaab" in "xaaab".

    	Example			matches
    	ab\{2,3}c		"abbc" or "abbbc"
    	a\{5}			"aaaaa"
    	ab\{2,}c		"abbc", "abbbc", "abbbbc", etc.
    	ab\{,3}c		"ac", "abc", "abbc" or "abbbc"
    	a[bc]\{3}d		"abbbd", "abbcd", "acbcd", "acccd", etc.
    	a\(bc\)\{1,2}d		"abcd" or "abcbcd"
    	a[bc]\{-}[cd]		"abc" in "abcd"
    	a[bc]*[cd]		"abcd" in "abcd"

    	The } may optionally be preceded with a backslash: \{n,m\}.

    							*/\@=*
    \@=	Matches the preceding atom with zero width.
    	Like "(?=pattern)" in Perl.
    	Example			matches
    	foo\(bar\)\@=		"foo" in "foobar"
    	foo\(bar\)\@=foo	nothing

    							*/zero-width*
    	When using "\@=" (or "^", "$", "\<", "\>") no characters are included
    	in the match.  These items are only used to check if a match can be
    	made.  This can be tricky, because a match with following items will
    	be done in the same position.  The last example above will not match
    	"foobarfoo", because it tries match "foo" in the same position where
    	"bar" matched.

    	Note that using "\&" works the same as using "\@=": "foo\&.." is the
    	same as "\(foo\)\@=..".  But using "\&" is easier, you don't need the
    	parentheses.

    							*/\@!*
    \@!	Matches with zero width if the preceding atom does NOT match at the
    	current position. |/zero-width|
    	Like "(?!pattern)" in Perl.
    	Example			matches
    	foo\(bar\)\@!		any "foo" not followed by "bar"
    	a.\{-}p\@!		"a", "ap", "app", "appp", etc. not immediately
    				followed by a "p"
    	if \(\(then\)\@!.\)*$	"if " not followed by "then"

    	Using "\@!" is tricky, because there are many places where a pattern
    	does not match.  "a.*p\@!" will match from an "a" to the end of the
    	line, because ".*" can match all characters in the line and the "p"
    	doesn't match at the end of the line.  "a.\{-}p\@!" will match any
    	"a", "ap", "app", etc. that isn't followed by a "p", because the "."
    	can match a "p" and "p\@!" doesn't match after that.

    	You can't use "\@!" to look for a non-match before the matching
    	position: "\(foo\)\@!bar" will match "bar" in "foobar", because at the
    	position where "bar" matches, "foo" does not match.  To avoid matching
    	"foobar" you could use "\(foo\)\@!...bar", but that doesn't match a
    	bar at the start of a line.  Use "\(foo\)\@<!bar".

    	Useful example: to find "foo" in a line that does not contain "bar":
    		/^\%(.*bar\)\@!.*\zsfoo
     	This pattern first checks that there is not a single position in the
    	line where "bar" matches.  If ".*bar" matches somewhere the \@! will
    	reject the pattern.  When there is no match any "foo" will be found.
    	The "\zs" is to have the match start just before "foo".

    							*/\@<=*
    \@<=	Matches with zero width if the preceding atom matches just before what
    	follows. |/zero-width|
    	Like "(?<=pattern)" in Perl, but Vim allows non-fixed-width patterns.
    	Example			matches
    	\(an\_s\+\)\@<=file	"file" after "an" and white space or an
    				end-of-line
    	For speed it's often much better to avoid this multi.  Try using "\zs"
    	instead |/\zs|.  To match the same as the above example:
    		an\_s\+\zsfile
    	At least set a limit for the look-behind, see below.

    	"\@<=" and "\@<!" check for matches just before what follows.
    	Theoretically these matches could start anywhere before this position.
    	But to limit the time needed, only the line where what follows matches
    	is searched, and one line before that (if there is one).  This should
    	be sufficient to match most things and not be too slow.

    	In the old regexp engine the part of the pattern after "\@<=" and
    	"\@<!" are checked for a match first, thus things like "\1" don't work
    	to reference \(\) inside the preceding atom.  It does work the other
    	way around:
    	Bad example			matches
    	\%#=1\1\@<=,\([a-z]\+\)		",abc" in "abc,abc"

    	However, the new regexp engine works differently, it is better to not
    	rely on this behavior, do not use \@<= if it can be avoided:
    	Example				matches
    	\([a-z]\+\)\zs,\1		",abc" in "abc,abc"

    \@123<=
    	Like "\@<=" but only look back 123 bytes. This avoids trying lots
    	of matches that are known to fail and make executing the pattern very
    	slow.  Example, check if there is a "<" just before "span":
    		/<\@1<=span
    	This will try matching "<" only one byte before "span", which is the
    	only place that works anyway.
    	After crossing a line boundary, the limit is relative to the end of
    	the line.  Thus the characters at the start of the line with the match
    	are not counted (this is just to keep it simple).
    	The number zero is the same as no limit.

    							*/\@<!*
    \@<!	Matches with zero width if the preceding atom does NOT match just
    	before what follows.  Thus this matches if there is no position in the
    	current or previous line where the atom matches such that it ends just
    	before what follows.  |/zero-width|
    	Like "(?<!pattern)" in Perl, but Vim allows non-fixed-width patterns.
    	The match with the preceding atom is made to end just before the match
    	with what follows, thus an atom that ends in ".*" will work.
    	Warning: This can be slow (because many positions need to be checked
    	for a match).  Use a limit if you can, see below.
    	Example			matches
    	\(foo\)\@<!bar		any "bar" that's not in "foobar"
    	\(\/\/.*\)\@<!in	"in" which is not after "//"

    \@123<!
    	Like "\@<!" but only look back 123 bytes. This avoids trying lots of
    	matches that are known to fail and make executing the pattern very
    	slow.

    							*/\@>*
    \@>	Matches the preceding atom like matching a whole pattern.
    	Like "(?>pattern)" in Perl.
    	Example		matches
    	\(a*\)\@>a	nothing (the "a*" takes all the "a"'s, there can't be
    			another one following)

    	This matches the preceding atom as if it was a pattern by itself.  If
    	it doesn't match, there is no retry with shorter sub-matches or
    	anything.  Observe this difference: "a*b" and "a*ab" both match
    	"aaab", but in the second case the "a*" matches only the first two
    	"a"s.  "\(a*\)\@>ab" will not match "aaab", because the "a*" matches
    	the "aaa" (as many "a"s as possible), thus the "ab" can't match.

    ==============================================================================

    6.  Ordinary atoms					*pattern-atoms*

    An ordinary atom can be:

    							*/^*
    ^	At beginning of pattern or after "\|", "\(", "\%(" or "\n": matches
    	start-of-line; at other positions, matches literal '^'. |/zero-width|
    	Example		matches
    	^beep(		the start of the C function "beep" (probably).

    							*/\^*
    \^	Matches literal '^'.  Can be used at any position in the pattern, but
    	not inside [].

    							*/\_^*
    \_^	Matches start-of-line. |/zero-width|  Can be used at any position in
    	the pattern, but not inside [].
    	Example		matches
    	\_s*\_^foo	white space and blank lines and then "foo" at
    			start-of-line

    							*/$*
    $	At end of pattern or in front of "\|", "\)" or "\n" ('magic' on):
    	matches end-of-line <EOL>; at other positions, matches literal '$'.
    	|/zero-width|

    							*/\$*
    \$	Matches literal '$'.  Can be used at any position in the pattern, but
    	not inside [].

    							*/\_$*
    \_$	Matches end-of-line. |/zero-width|  Can be used at any position in the
    	pattern, but not inside [].  Note that "a\_$b" never matches, since
    	"b" cannot match an end-of-line.  Use "a\nb" instead |/\n|.
    	Example		matches
    	foo\_$\_s*	"foo" at end-of-line and following white space and
    			blank lines

    .	(with 'nomagic': \.)				*/.* */\.*
    	Matches any single character, but not an end-of-line.

    							*/\_.*
    \_.	Matches any single character or end-of-line.
    	Careful: "\_.*" matches all text to the end of the buffer!

    							*/\<*
    \<	Matches the beginning of a word: The next char is the first char of a
    	word.  The 'iskeyword' option specifies what is a word character.
    	|/zero-width|

    							*/\>*
    \>	Matches the end of a word: The previous char is the last char of a
    	word.  The 'iskeyword' option specifies what is a word character.
    	|/zero-width|

    							*/\zs*
    \zs	Matches at any position, but not inside [], and sets the start of the
    	match there: The next char is the first char of the whole match.
    	|/zero-width|
    	Example:
    		/^\s*\zsif
     	matches an "if" at the start of a line, ignoring white space.
    	Can be used multiple times, the last one encountered in a matching
    	branch is used.  Example:
    		/\(.\{-}\zsFab\)\{3}
     	Finds the third occurrence of "Fab".

    	This cannot be followed by a multi. *E888*
    	{not available when compiled without the |+syntax| feature}

    							*/\ze*
    \ze	Matches at any position, but not inside [], and sets the end of the
    	match there: The previous char is the last char of the whole match.
    	|/zero-width|
    	Can be used multiple times, the last one encountered in a matching
    	branch is used.
    	Example: "end\ze\(if\|for\)" matches the "end" in "endif" and
    	"endfor".
    	This cannot be followed by a multi. |E888|
    	{not available when compiled without the |+syntax| feature}

    						*/\%^* *start-of-file*
    \%^	Matches start of the file.  When matching with a string, matches the
    	start of the string.
    	For example, to find the first "VIM" in a file:
    		/\%^\_.\{-}\zsVIM

    						*/\%$* *end-of-file*
    \%$	Matches end of the file.  When matching with a string, matches the
    	end of the string.
    	Note that this does NOT find the last "VIM" in a file:
    		/VIM\_.\{-}\%$
     	It will find the next VIM, because the part after it will always
    	match.  This one will find the last "VIM" in the file:
    		/VIM\ze\(\(VIM\)\@!\_.\)*\%$
     	This uses |/\@!| to ascertain that "VIM" does NOT match in any
    	position after the first "VIM".
    	Searching from the end of the file backwards is easier!

    						*/\%V*
    \%V	Match inside the Visual area.  When Visual mode has already been
    	stopped match in the area that |gv| would reselect.
    	This is a |/zero-width| match.  To make sure the whole pattern is
    	inside the Visual area put it at the start and just before the end of
    	the pattern, e.g.:
    		/\%Vfoo.*ba\%Vr
     	This also works if only "foo bar" was Visually selected. This:
    		/\%Vfoo.*bar\%V
     	would match "foo bar" if the Visual selection continues after the "r".
    	Only works for the current buffer.

    						*/\%#* *cursor-position*
    \%#	Matches with the cursor position.  Only works when matching in a
    	buffer displayed in a window.
    	WARNING: When the cursor is moved after the pattern was used, the
    	result becomes invalid.  Vim doesn't automatically update the matches.
    	This is especially relevant for syntax highlighting and 'hlsearch'.
    	In other words: When the cursor moves the display isn't updated for
    	this change.  An update is done for lines which are changed (the whole
    	line is updated) or when using the |CTRL-L| command (the whole screen
    	is updated).  Example, to highlight the word under the cursor:
    		/\k*\%#\k*
     	When 'hlsearch' is set and you move the cursor around and make changes
    	this will clearly show when the match is updated or not.

    						*/\%'m* */\%<'m* */\%>'m*
    \%'m	Matches with the position of mark m.
    \%<'m	Matches before the position of mark m.
    \%>'m	Matches after the position of mark m.
    	Example, to highlight the text from mark 's to 'e:
    		/.\%>'s.*\%<'e..
     	Note that two dots are required to include mark 'e in the match.  That
    	is because "\%<'e" matches at the character before the 'e mark, and
    	since it's a |/zero-width| match it doesn't include that character.
    	WARNING: When the mark is moved after the pattern was used, the result
    	becomes invalid.  Vim doesn't automatically update the matches.
    	Similar to moving the cursor for "\%#" |/\%#|.

    						*/\%l* */\%>l* */\%<l* *E951*
    \%23l	Matches in a specific line.
    \%<23l	Matches above a specific line (lower line number).
    \%>23l	Matches below a specific line (higher line number).
    \%.l    Matches at the cursor line.
    \%<.l   Matches above the cursor line.
    \%>.l   Matches below the cursor line.
    	These six can be used to match specific lines in a buffer.  The "23"
    	can be any line number.  The first line is 1.
    	WARNING: When inserting or deleting lines Vim does not automatically
    	update the matches.  This means Syntax highlighting quickly becomes
    	wrong.  Also when referring to the cursor position (".") and
    	the cursor moves the display isn't updated for this change.  An update
    	is done when using the |CTRL-L| command (the whole screen is updated).
    	Example, to highlight the line where the cursor currently is:
    		:exe '/\%' . line(".") . 'l'
     	Alternatively use:
    		/\%.l
     	When 'hlsearch' is set and you move the cursor around and make changes
    	this will clearly show when the match is updated or not.

    						*/\%c* */\%>c* */\%<c*
    \%23c	Matches in a specific column.
    \%<23c	Matches before a specific column.
    \%>23c	Matches after a specific column.
    \%.c    Matches at the cursor column.
    \%<.c   Matches before the cursor column.
    \%>.c   Matches after the cursor column.
    	These six can be used to match specific columns in a buffer or string.
    	The "23" can be any column number.  The first column is 1.  Actually,
    	the column is the byte number (thus it's not exactly right for
    	multibyte characters).
    	WARNING: When inserting or deleting text Vim does not automatically
    	update the matches.  This means Syntax highlighting quickly becomes
    	wrong.  Also when referring to the cursor position (".") and
    	the cursor moves the display isn't updated for this change.  An update
    	is done when using the |CTRL-L| command (the whole screen is updated).
    	Example, to highlight the column where the cursor currently is:
    		:exe '/\%' . col(".") . 'c'
     	Alternatively use:
    		/\%.c
     	When 'hlsearch' is set and you move the cursor around and make changes
    	this will clearly show when the match is updated or not.
    	Example for matching a single byte in column 44:
    		/\%>43c.\%<46c
     	Note that "\%<46c" matches in column 45 when the "." matches a byte in
    	column 44.

    						*/\%v* */\%>v* */\%<v*
    \%23v	Matches in a specific virtual column.
    \%<23v	Matches before a specific virtual column.
    \%>23v	Matches after a specific virtual column.
    \%.v    Matches at the current virtual column.
    \%<.v   Matches before the current virtual column.
    \%>.v   Matches after the current virtual column.
    	These six can be used to match specific virtual columns in a buffer or
    	string.  When not matching with a buffer in a window, the option
    	values of the current window are used (e.g., 'tabstop').
    	The "23" can be any column number.  The first column is 1.
    	Note that some virtual column positions will never match, because they
    	are halfway through a tab or other character that occupies more than
    	one screen character.
    	WARNING: When inserting or deleting text Vim does not automatically
    	update highlighted matches.  This means Syntax highlighting quickly
    	becomes wrong.  Also when referring to the cursor position (".") and
    	the cursor moves the display isn't updated for this change.  An update
    	is done when using the |CTRL-L| command (the whole screen is updated).
    	Example, to highlight all the characters after virtual column 72:
    		/\%>72v.*
     	When 'hlsearch' is set and you move the cursor around and make changes
    	this will clearly show when the match is updated or not.
    	To match the text up to column 17:
    		/^.*\%17v
     	To match all characters after the current virtual column (where the
    	cursor is):
    		/\%>.v.*
     	Column 17 is not included, because this is a |/zero-width| match. To
    	include the column use:
    		/^.*\%17v.
     	This command does the same thing, but also matches when there is no
    	character in column 17:
    		/^.*\%<18v.
     	Note that without the "^" to anchor the match in the first column,
    	this will also highlight column 17:
    		/.*\%17v
     	Column 17 is highlighted by 'hlsearch' because there is another match
    	where ".*" matches zero characters.

    Character classes:

    \i	identifier character (see 'isident' option)	*/\i*

    \I	like "\i", but excluding digits			*/\I*

    \k	keyword character (see 'iskeyword' option)	*/\k*

    \K	like "\k", but excluding digits			*/\K*

    \f	file name character (see 'isfname' option)	*/\f*

    \F	like "\f", but excluding digits			*/\F*

    \p	printable character (see 'isprint' option)	*/\p*

    \P	like "\p", but excluding digits			*/\P*

    NOTE: the above also work for multibyte characters.  The ones below only
    match ASCII characters, as indicated by the range.

    						*whitespace* *white-space*

    \s	whitespace character: <Space> and <Tab>		*/\s*

    \S	non-whitespace character; opposite of \s	*/\S*

    \d	digit:				[0-9]		*/\d*

    \D	non-digit:			[^0-9]		*/\D*

    \x	hex digit:			[0-9A-Fa-f]	*/\x*

    \X	non-hex digit:			[^0-9A-Fa-f]	*/\X*

    \o	octal digit:			[0-7]		*/\o*

    \O	non-octal digit:		[^0-7]		*/\O*

    \w	word character:			[0-9A-Za-z_]	*/\w*

    \W	non-word character:		[^0-9A-Za-z_]	*/\W*

    \h	head of word character:		[A-Za-z_]	*/\h*

    \H	non-head of word character:	[^A-Za-z_]	*/\H*

    \a	alphabetic character:		[A-Za-z]	*/\a*

    \A	non-alphabetic character:	[^A-Za-z]	*/\A*

    \l	lowercase character:		[a-z]		*/\l*

    \L	non-lowercase character:	[^a-z]		*/\L*

    \u	uppercase character:		[A-Z]		*/\u*

    \U	non-uppercase character:	[^A-Z]		*/\U*

    	NOTE: Using the atom is faster than the [] form.

    	NOTE: 'ignorecase', "\c" and "\C" are not used by character classes.

    			*/\_* *E63* */\_i* */\_I* */\_k* */\_K* */\_f* */\_F*

    			*/\_p* */\_P* */\_s* */\_S* */\_d* */\_D* */\_x* */\_X*

    			*/\_o* */\_O* */\_w* */\_W* */\_h* */\_H* */\_a* */\_A*

    			*/\_l* */\_L* */\_u* */\_U*
    \_x	Where "x" is any of the characters above: The character class with
    	end-of-line added
    (end of character classes)

    \e	matches <Esc>					*/\e*

    \t	matches <Tab>					*/\t*

    \r	matches <CR>					*/\r*

    \b	matches <BS>					*/\b*

    \n	matches an end-of-line				*/\n*
    	When matching in a string instead of buffer text a literal newline
    	character is matched.

    ~	matches the last given substitute string	*/~* */\~*

    \(\)	A pattern enclosed by escaped parentheses.	*/\(* */\(\)* */\)*
    	E.g., "\(^a\)" matches 'a' at the start of a line.

    	*E51* *E54* *E55* *E872* *E873*

    \1      Matches the same string that was matched by	*/\1* *E65*
    	the first sub-expression in \( and \).
    	Example: "\([a-z]\).\1" matches "ata", "ehe", "tot", etc.

    \2      Like "\1", but uses second sub-expression,	*/\2*

       ...							*/\3*

    \9      Like "\1", but uses ninth sub-expression.	*/\9*
    	Note: The numbering of groups is done based on which "\(" comes first
    	in the pattern (going left to right), NOT based on what is matched
    	first.

    \%(\)	A pattern enclosed by escaped parentheses.	*/\%(\)* */\%(* *E53*
    	Just like \(\), but without counting it as a sub-expression.  This
    	allows using more groups and it's a little bit faster.

    x	A single character, with no special meaning, matches itself

    							*/\* */\\*
    \x	A backslash followed by a single character, with no special meaning,
    	is reserved for future expansions

    []	(with 'nomagic': \[])		*/[]* */\[]* */\_[]* */collection*
    \_[]
    	A collection.  This is a sequence of characters enclosed in square
    	brackets.  It matches any single character in the collection.
    	Example		matches
    	[xyz]		any 'x', 'y' or 'z'
    	[a-zA-Z]$	any alphabetic character at the end of a line
    	\c[a-z]$	same
    	[А-яЁё]		Russian alphabet (with utf-8 and cp1251)

    								*/[\n]*
    	With "\_" prepended the collection also includes the end-of-line.
    	The same can be done by including "\n" in the collection.  The
    	end-of-line is also matched when the collection starts with "^"!  Thus
    	"\_[^ab]" matches the end-of-line and any character but "a" and "b".
    	This makes it Vi compatible: Without the "\_" or "\n" the collection
    	does not match an end-of-line.

    								*E769*
    	When the ']' is not there Vim will not give an error message but
    	assume no collection is used.  Useful to search for '['.  However, you
    	do get E769 for internal searching.  And be aware that in a
    	`:substitute` command the whole command becomes the pattern.  E.g.
    	":s/[/x/" searches for "[/x" and replaces it with nothing.  It does
    	not search for "[" and replaces it with "x"!

    								*E944* *E945*
    	If the sequence begins with "^", it matches any single character NOT
    	in the collection: "[^xyz]" matches anything but 'x', 'y' and 'z'.
    	- If two characters in the sequence are separated by '-', this is
    	  shorthand for the full list of ASCII characters between them.  E.g.,
    	  "[0-9]" matches any decimal digit. If the starting character exceeds
    	  the ending character, e.g. [c-a], E944 occurs. Non-ASCII characters
    	  can be used, but the character values must not be more than 256 apart
    	  in the old regexp engine. For example, searching by [\u3000-\u4000]
    	  after setting re=1 emits a E945 error. Prepending \%#=2 will fix it.
    	- A character class expression is evaluated to the set of characters
    	  belonging to that character class.  The following character classes
    	  are supported:
    		  Name	      Func	Contents

    *[:alnum:]*	  [:alnum:]   isalnum	ASCII letters and digits

    *[:alpha:]*	  [:alpha:]   isalpha  	ASCII letters

    *[:blank:]*	  [:blank:]     	space and tab

    *[:cntrl:]*	  [:cntrl:]   iscntrl 	ASCII control characters

    *[:digit:]*	  [:digit:]     	decimal digits '0' to '9'

    *[:graph:]*	  [:graph:]   isgraph	ASCII printable characters excluding
    					space

    *[:lower:]*	  [:lower:]   (1)	lowercase letters (all letters when
    					'ignorecase' is used)

    *[:print:]*	  [:print:]   (2) 	printable characters including space

    *[:punct:]*	  [:punct:]   ispunct	ASCII punctuation characters

    *[:space:]*	  [:space:]     	whitespace characters: space, tab, CR,
    					NL, vertical tab, form feed

    *[:upper:]*	  [:upper:]   (3)	uppercase letters (all letters when
    					'ignorecase' is used)

    *[:xdigit:]*	  [:xdigit:]    	hexadecimal digits: 0-9, a-f, A-F

    *[:return:]*	  [:return:]		the <CR> character

    *[:tab:]*	  [:tab:]		the <Tab> character

    *[:escape:]*	  [:escape:]		the <Esc> character

    *[:backspace:]*	  [:backspace:]		the <BS> character

    *[:ident:]*	  [:ident:]		identifier character (same as "\i")

    *[:keyword:]*	  [:keyword:]		keyword character (same as "\k")

    *[:fname:]*	  [:fname:]		file name character (same as "\f")
    	  The square brackets in character class expressions are additional to
    	  the square brackets delimiting a collection.  For example, the
    	  following is a plausible pattern for a UNIX filename:
    	  "[-./[:alnum:]_~]\+".  That is, a list of at least one character,
    	  each of which is either '-', '.', '/', alphabetic, numeric, '_' or
    	  '~'.
    	  These items only work for 8-bit characters, except [:lower:] and
    	  [:upper:] also work for multibyte characters when using the new
    	  regexp engine.  See |two-engines|.  In the future these items may
    	  work for multibyte characters.  For now, to get all "alpha"
    	  characters you can use: [[:lower:][:upper:]].

    	  The "Func" column shows what library function is used.  The
    	  implementation depends on the system.  Otherwise:
    	  (1) Uses islower() for ASCII and Vim builtin rules for other
    	  characters.
    	  (2) Uses Vim builtin rules
    	  (3) As with (1) but using isupper()

    							*/[[=* *[==]*
    	- An equivalence class.  This means that characters are matched that
    	  have almost the same meaning, e.g., when ignoring accents.  This
    	  only works for Unicode, latin1 and latin9.  The form is:
    		[=a=]

    							*/[[.* *[..]*
    	- A collation element.  This currently simply accepts a single
    	  character in the form:
    		[.a.]

    							  */\]*
    	- To include a literal ']', '^', '-' or '\' in the collection, put a
    	  backslash before it: "[xyz\]]", "[\^xyz]", "[xy\-z]" and "[xyz\\]".
    	  (Note: POSIX does not support the use of a backslash this way).  For
    	  ']' you can also make it the first character (following a possible
    	  "^"):  "[]xyz]" or "[^]xyz]".
    	  For '-' you can also make it the first or last character: "[-xyz]",
    	  "[^-xyz]" or "[xyz-]".  For '\' you can also let it be followed by
    	  any character that's not in "^]-\bdertnoUux".  "[\xyz]" matches '\',
    	  'x', 'y' and 'z'.  It's better to use "\\" though, future expansions
    	  may use other characters after '\'.
    	- Omitting the trailing ] is not considered an error. "[]" works like
    	  "[]]", it matches the ']' character.
    	- The following translations are accepted when the 'l' flag is not
    	  included in 'cpoptions':
    		\e	<Esc>
    		\t	<Tab>
    		\r	<CR>	(NOT end-of-line!)
    		\b	<BS>
    		\n	line break, see above |/[\n]|
    		\d123	decimal number of character
    		\o40	octal number of character up to 0o377
    		\x20	hexadecimal number of character up to 0xff
    		\u20AC	hex. number of multibyte character up to 0xffff
    		\U1234	hex. number of multibyte character up to 0xffffffff
    	  NOTE: The other backslash codes mentioned above do not work inside
    	  []!
    	- Matching with a collection can be slow, because each character in
    	  the text has to be compared with each character in the collection.
    	  Use one of the other atoms above when possible.  Example: "\d" is
    	  much faster than "[0-9]" and matches the same characters.  However,
    	  the new |NFA| regexp engine deals with this better than the old one.

    						*/\%[]* *E69* *E70* *E369*
    \%[]	A sequence of optionally matched atoms.  This always matches.
    	It matches as much of the list of atoms it contains as possible.  Thus
    	it stops at the first atom that doesn't match.  For example:
    		/r\%[ead]
     	matches "r", "re", "rea" or "read".  The longest that matches is used.
    	To match the Ex command "function", where "fu" is required and
    	"nction" is optional, this would work:
    		/\<fu\%[nction]\>
     	The end-of-word atom "\>" is used to avoid matching "fu" in "full".
    	It gets more complicated when the atoms are not ordinary characters.
    	You don't often have to use it, but it is possible.  Example:
    		/\<r\%[[eo]ad]\>
     	Matches the words "r", "re", "ro", "rea", "roa", "read" and "road".
    	There can be no \(\), \%(\) or \z(\) items inside the [] and \%[] does
    	not nest.
    	To include a "[" use "[[]" and for "]" use []]", e.g.,:
    		/index\%[[[]0[]]]
     	matches "index" "index[", "index[0" and "index[0]".
    	{not available when compiled without the |+syntax| feature}

    				*/\%d* */\%x* */\%o* */\%u* */\%U* *E678*

    \%d123	Matches the character specified with a decimal number.  Must be
    	followed by a non-digit.
    \%o40	Matches the character specified with an octal number up to 0o377.
    	Numbers below 0o40 must be followed by a non-octal digit or a
    	non-digit.
    \%x2a	Matches the character specified with up to two hexadecimal characters.
    \%u20AC	Matches the character specified with up to four hexadecimal
    	characters.
    \%U1234abcd	Matches the character specified with up to eight hexadecimal
    	characters, up to 0x7fffffff

    ==============================================================================

    7. Ignoring case in a pattern					*/ignorecase*

    If the 'ignorecase' option is on, the case of normal letters is ignored.
    'smartcase' can be set to ignore case when the pattern contains lowercase
    letters only.

    							*/\c* */\C*
    When "\c" appears anywhere in the pattern, the whole pattern is handled like
    'ignorecase' is on.  The actual value of 'ignorecase' and 'smartcase' is
    ignored.  "\C" does the opposite: Force matching case for the whole pattern.
    {only Vim supports \c and \C}
    Note that 'ignorecase', "\c" and "\C" are not used for the character classes.

    Examples:
          pattern	'ignorecase'  'smartcase'	matches
    	foo	  off		-		foo
    	foo	  on		-		foo Foo FOO
    	Foo	  on		off		foo Foo FOO
    	Foo	  on		on		    Foo
    	\cfoo	  -		-		foo Foo FOO
    	foo\C	  -		-		foo

    Technical detail:				*NL-used-for-Nul*
    <Nul> characters in the file are stored as <NL> in memory.  In the display
    they are shown as "^@".  The translation is done when reading and writing
    files.  To match a <Nul> with a search pattern you can just enter CTRL-@ or
    "CTRL-V 000".  This is probably just what you expect.  Internally the
    character is replaced with a <NL> in the search pattern.  What is unusual is
    that typing CTRL-V CTRL-J also inserts a <NL>, thus also searches for a <Nul>
    in the file.

    						*CR-used-for-NL*
    When 'fileformat' is "mac", <NL> characters in the file are stored as <CR>
    characters internally.  In the text they are shown as "^J".  Otherwise this
    works similar to the usage of <NL> for a <Nul>.

    When working with expression evaluation, a <NL> character in the pattern
    matches a <NL> in the string.  The use of "\n" (backslash n) to match a <NL>
    doesn't work there, it only works to match text in the buffer.

    				*pattern-multi-byte* *pattern-multibyte*
    Patterns will also work with multibyte characters, mostly as you would
    expect.  But invalid bytes may cause trouble, a pattern with an invalid byte
    will probably never match.

    ==============================================================================

    8. Composing characters					*patterns-composing*

    							*/\Z*
    When "\Z" appears anywhere in the pattern, all composing characters are
    ignored.  Thus only the base characters need to match, the composing
    characters may be different and the number of composing characters may differ.
    Only relevant when 'encoding' is "utf-8".
    Exception: If the pattern starts with one or more composing characters, these
    must match.

    							*/\%C*
    Use "\%C" to skip any composing characters.  For example, the pattern "a" does
    not match in "càt" (where the a has the composing character 0x0300), but
    "a\%C" does.  Note that this does not match "cát" (where the á is character
    0xe1, it does not have a compositing character).  It does match "cat" (where
    the a is just an a).

    When a composing character appears at the start of the pattern or after an
    item that doesn't include the composing character, a match is found at any
    character that includes this composing character.

    When using a dot and a composing character, this works the same as the
    composing character by itself, except that it doesn't matter what comes before
    this.

    The order of composing characters does not matter.  Also, the text may have
    more composing characters than the pattern, it still matches.  But all
    composing characters in the pattern must be found in the text.

    Suppose B is a base character and x and y are composing characters:
    	pattern		text		match
    	Bxy		Bxy		yes (perfect match)
    	Bxy		Byx		yes (order ignored)
    	Bxy		By		no (x missing)
    	Bxy		Bx		no (y missing)
    	Bx		Bx		yes (perfect match)
    	Bx		By		no (x missing)
    	Bx		Bxy		yes (extra y ignored)
    	Bx		Byx		yes (extra y ignored)

    ==============================================================================

    9. Compare with Perl patterns				*perl-patterns*

    Vim's regexes are most similar to Perl's, in terms of what you can do.  The
    difference between them is mostly just notation;  here's a summary of where
    they differ:

    Capability			in Vimspeak	in Perlspeak
    force case insensitivity	\c		(?i)
    force case sensitivity		\C		(?-i)
    backref-less grouping		\%(atom\)	(?:atom)
    conservative quantifiers	\{-n,m}		*?, +?, ??, {}?
    0-width match			atom\@=		(?=atom)
    0-width non-match		atom\@!		(?!atom)
    0-width preceding match		atom\@<=	(?<=atom)
    0-width preceding non-match	atom\@<!	(?<!atom)
    match without retry		atom\@>		(?>atom)

    Vim and Perl handle newline characters inside a string a bit differently:

    In Perl, ^ and $ only match at the very beginning and end of the text,
    by default, but you can set the 'm' flag, which lets them match at
    embedded newlines as well.  You can also set the 's' flag, which causes
    a . to match newlines as well.  (Both these flags can be changed inside
    a pattern using the same syntax used for the i flag above, BTW.)

    On the other hand, Vim's ^ and $ always match at embedded newlines, and
    you get two separate atoms, \%^ and \%$, which only match at the very
    start and end of the text, respectively.  Vim solves the second problem
    by giving you the \_ "modifier":  put it in front of a . or a character
    class, and they will match newlines as well.

    Finally, these constructs are unique to Perl:
    - execution of arbitrary code in the regex:  (?{perl code})
    - conditional expressions:  (?(condition)true-expr|false-expr)

    ...and these are unique to Vim:
    - changing the magic-ness of a pattern:  \v \V \m \M
       (very useful for avoiding backslashitis)
    - sequence of optionally matching atoms:  \%[atoms]
    - \& (which is to \| what "and" is to "or";  it forces several branches
       to match at one spot)
    - matching lines/columns by number:  \%5l \%5c \%5v
    - setting the start and end of the match:  \zs \ze

    ==============================================================================

    10. Highlighting matches				*match-highlight*

    							*:mat* *:match*
    :mat[ch] {group} /{pattern}/
    		Define a pattern to highlight in the current window.  It will
    		be highlighted with {group}.  Example:
    			:highlight MyGroup ctermbg=green guibg=green
    			:match MyGroup /TODO/
     		Instead of // any character can be used to mark the start and
    		end of the {pattern}.  Watch out for using special characters,
    		such as '"'' and '|'.

    		{group} must exist at the moment this command is executed.

    		The {group} highlighting still applies when a character is
    		to be highlighted for 'hlsearch', as the highlighting for
    		matches is given higher priority than that of 'hlsearch'.
    		Syntax highlighting (see 'syntax') is also overruled by
    		matches.

    		Note that highlighting the last used search pattern with
    		'hlsearch' is used in all windows, while the pattern defined
    		with ":match" only exists in the current window.  It is kept
    		when switching to another buffer.

    		'ignorecase' does not apply, use |/\c| in the pattern to
    		ignore case.  Otherwise case is not ignored.

    		'redrawtime' defines the maximum time searched for pattern
    		matches.

    		When matching end-of-line and Vim redraws only part of the
    		display you may get unexpected results.  That is because Vim
    		looks for a match in the line where redrawing starts.

    		Also see |matcharg()| and |getmatches()|. The former returns
    		the highlight group and pattern of a previous |:match|
    		command.  The latter returns a list with highlight groups and
    		patterns defined by both |matchadd()| and |:match|.

    		Highlighting matches using |:match| are limited to three
    		matches (aside from |:match|, |:2match| and |:3match| are
    		available). |matchadd()| does not have this limitation and in
    		addition makes it possible to prioritize matches.

    		Another example, which highlights all characters in virtual
    		column 72 and more:
    			:highlight rightMargin term=bold ctermfg=blue guifg=blue
    			:match rightMargin /.\%>72v/
     		To highlight all character that are in virtual column 7:
    			:highlight col8 ctermbg=grey guibg=grey
    			:match col8 /\%<8v.\%>7v/
     		Note the use of two items to also match a character that
    		occupies more than one virtual column, such as a TAB.

    :mat[ch]
    :mat[ch] none
    		Clear a previously defined match pattern.

    :2mat[ch] {group} /{pattern}/					*:2match*
    :2mat[ch]
    :2mat[ch] none

    :3mat[ch] {group} /{pattern}/					*:3match*
    :3mat[ch]
    :3mat[ch] none
    		Just like |:match| above, but set a separate match.  Thus
    		there can be three matches active at the same time.  The match
    		with the lowest number has priority if several match at the
    		same position.
    		The ":3match" command is used by the |matchparen| plugin.  You
    		are suggested to use ":match" for manual matching and
    		":2match" for another plugin.

    ==============================================================================

    11. Fuzzy matching					*fuzzy-match*

    Fuzzy matching refers to matching strings using a non-exact search string.
    Fuzzy matching will match a string, if all the characters in the search string
    are present anywhere in the string in the same order. Case is ignored.  In a
    matched string, other characters can be present between two consecutive
    characters in the search string. If the search string has multiple words, then
    each word is matched separately. So the words in the search string can be
    present in any order in a string.

    Fuzzy matching assigns a score for each matched string based on the following
    criteria:
        - The number of sequentially matching characters.
        - The number of characters (distance) between two consecutive matching
          characters.
        - Matches at the beginning of a word
        - Matches at a camel case character (e.g. Case in CamelCase)
        - Matches after a path separator or a hyphen.
        - The number of unmatched characters in a string.
    The matching string with the highest score is returned first.

    For example, when you search for the "get pat" string using fuzzy matching, it
    will match the strings "GetPattern", "PatternGet", "getPattern", "patGetter",
    "getSomePattern", "MatchpatternGet" etc.

    The functions |matchfuzzy()| and |matchfuzzypos()| can be used to fuzzy search
    a string in a List of strings. The matchfuzzy() function returns a List of
    matching strings. The matchfuzzypos() functions returns the List of matches,
    the matching positions and the fuzzy match scores.

    The "f" flag of `:vimgrep` enables fuzzy matching.

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