VIM: usr_27

## USR_27

    *usr_27.txt*	For Vim version 8.2.  Last change: 2019 Jul 14

    		     VIM USER MANUAL - by Bram Moolenaar

    			 Search commands and patterns

    In chapter 3 a few simple search patterns were mentioned |03.9|.  Vim can do
    much more complex searches.  This chapter explains the most often used ones.
    A detailed specification can be found here: |pattern|

    |27.1|	Ignoring case
    |27.2|	Wrapping around the file end
    |27.3|	Offsets
    |27.4|	Matching multiple times
    |27.5|	Alternatives
    |27.6|	Character ranges
    |27.7|	Character classes
    |27.8|	Matching a line break
    |27.9|	Examples

         Next chapter: |usr_28|  Folding
     Previous chapter: |usr_26|  Repeating
    Table of contents: |usr_toc|

    *27.1*	Ignoring case

    By default, Vim's searches are case sensitive.  Therefore, "include",
    "INCLUDE", and "Include" are three different words and a search will match
    only one of them.
       Now switch on the 'ignorecase' option:

    	:set ignorecase

    Search for "include" again, and now it will match "Include", "INCLUDE" and
    "InClUDe".  (Set the 'hlsearch' option to quickly see where a pattern
    matches.)
       You can switch this off again with:

    	:set noignorecase

    But let's keep it set, and search for "INCLUDE".  It will match exactly the
    same text as "include" did.  Now set the 'smartcase' option:

    	:set ignorecase smartcase

    If you have a pattern with at least one uppercase character, the search
    becomes case sensitive.  The idea is that you didn't have to type that
    uppercase character, so you must have done it because you wanted case to
    match.  That's smart!
        With these two options set you find the following matches:

    	pattern			matches
    	word			word, Word, WORD, WoRd, etc.
    	Word			Word
    	WORD			WORD
    	WoRd			WoRd

    CASE IN ONE PATTERN

    If you want to ignore case for one specific pattern, you can do this by
    prepending the "\c" string.  Using "\C" will make the pattern to match case.
    This overrules the 'ignorecase' and 'smartcase' options, when "\c" or "\C" is
    used their value doesn't matter.

    	pattern			matches
    	\Cword			word
    	\CWord			Word
    	\cword			word, Word, WORD, WoRd, etc.
    	\cWord			word, Word, WORD, WoRd, etc.

    A big advantage of using "\c" and "\C" is that it sticks with the pattern.
    Thus if you repeat a pattern from the search history, the same will happen, no
    matter if 'ignorecase' or 'smartcase' was changed.

    	Note:
    	The use of "\" items in search patterns depends on the 'magic' option.
    	In this chapter we will assume 'magic' is on, because that is the
    	standard and recommended setting.  If you would change 'magic', many
    	search patterns would suddenly become invalid.

    	Note:
    	If your search takes much longer than you expected, you can interrupt
    	it with CTRL-C on Unix and CTRL-Break on MS-Windows.

    *27.2*	Wrapping around the file end

    By default, a forward search starts searching for the given string at the
    current cursor location.  It then proceeds to the end of the file.  If it has
    not found the string by that time, it starts from the beginning and searches
    from the start of the file to the cursor location.
       Keep in mind that when repeating the "n" command to search for the next
    match, you eventually get back to the first match.  If you don't notice this
    you keep searching forever!  To give you a hint, Vim displays this message:

    	search hit BOTTOM, continuing at TOP

    If you use the "?" command, to search in the other direction, you get this
    message:

    	search hit TOP, continuing at BOTTOM

    Still, you don't know when you are back at the first match.  One way to see
    this is by switching on the 'ruler' option:

    	:set ruler

    Vim will display the cursor position in the lower righthand corner of the
    window (in the status line if there is one).  It looks like this:

    	101,29       84%

    The first number is the line number of the cursor.  Remember the line number
    where you started, so that you can check if you passed this position again.

    NOT WRAPPING

    To turn off search wrapping, use the following command:

    	:set nowrapscan

    Now when the search hits the end of the file, an error message displays:

    	E385: search hit BOTTOM without match for: forever

    Thus you can find all matches by going to the start of the file with "gg" and
    keep searching until you see this message.
       If you search in the other direction, using "?", you get:

    	E384: search hit TOP without match for: forever

    *27.3*	Offsets

    By default, the search command leaves the cursor positioned on the beginning
    of the pattern.  You can tell Vim to leave it some other place by specifying
    an offset.  For the forward search command "/", the offset is specified by
    appending a slash (/) and the offset:

    	/default/2

    This command searches for the pattern "default" and then moves to the
    beginning of the second line past the pattern.  Using this command on the
    paragraph above, Vim finds the word "default" in the first line.  Then the
    cursor is moved two lines down and lands on "an offset".

    If the offset is a simple number, the cursor will be placed at the beginning
    of the line that many lines from the match.  The offset number can be positive
    or negative.  If it is positive, the cursor moves down that many lines; if
    negative, it moves up.

    CHARACTER OFFSETS

    The "e" offset indicates an offset from the end of the match.  It moves the
    cursor onto the last character of the match.  The command:

    	/const/e

    puts the cursor on the "t" of "const".
       From that position, adding a number moves forward that many characters.
    This command moves to the character just after the match:

    	/const/e+1

    A positive number moves the cursor to the right, a negative number moves it to
    the left.  For example:

    	/const/e-1

    moves the cursor to the "s" of "const".

    If the offset begins with "b", the cursor moves to the beginning of the
    pattern.  That's not very useful, since leaving out the "b" does the same
    thing.  It does get useful when a number is added or subtracted.  The cursor
    then goes forward or backward that many characters.  For example:

    	/const/b+2

    Moves the cursor to the beginning of the match and then two characters to the
    right.  Thus it lands on the "n".

    REPEATING

    To repeat searching for the previously used search pattern, but with a
    different offset, leave out the pattern:

    	/that
    	//e

    Is equal to:

    	/that/e

    To repeat with the same offset:

    	/

    "n" does the same thing.  To repeat while removing a previously used offset:

    	//

    SEARCHING BACKWARDS

    The "?" command uses offsets in the same way, but you must use "?" to separate
    the offset from the pattern, instead of "/":

    	?const?e-2

    The "b" and "e" keep their meaning, they don't change direction with the use
    of "?".

    START POSITION

    When starting a search, it normally starts at the cursor position.  When you
    specify a line offset, this can cause trouble.  For example:

    	/const/-2

    This finds the next word "const" and then moves two lines up.  If you
    use "n" to search again, Vim could start at the current position and find the
    same "const" match.  Then using the offset again, you would be back where you
    started.  You would be stuck!
       It could be worse: Suppose there is another match with "const" in the next
    line.  Then repeating the forward search would find this match and move two
    lines up.  Thus you would actually move the cursor back!

    When you specify a character offset, Vim will compensate for this.  Thus the
    search starts a few characters forward or backward, so that the same match
    isn't found again.

    *27.4*	Matching multiple times

    The "*" item specifies that the item before it can match any number of times.
    Thus:

    	/a*

    matches "a", "aa", "aaa", etc.  But also "" (the empty string), because zero
    times is included.
       The "*" only applies to the item directly before it.  Thus "ab*" matches
    "a", "ab", "abb", "abbb", etc.  To match a whole string multiple times, it
    must be grouped into one item.  This is done by putting "\(" before it and
    "\)" after it.  Thus this command:

    	/\(ab\)*

    Matches: "ab", "abab", "ababab", etc.  And also "".

    To avoid matching the empty string, use "\+".  This makes the previous item
    match one or more times.

    	/ab\+

    Matches "ab", "abb", "abbb", etc.  It does not match "a" when no "b" follows.

    To match an optional item, use "\=".  Example:

    	/folders\=

    Matches "folder" and "folders".

    SPECIFIC COUNTS

    To match a specific number of items use the form "\{n,m}".  "n" and "m" are
    numbers.  The item before it will be matched "n" to "m" times |inclusive|.
    Example:

    	/ab\{3,5}

    matches "abbb", "abbbb" and "abbbbb".
      When "n" is omitted, it defaults to zero.  When "m" is omitted it defaults
    to infinity.  When ",m" is omitted, it matches exactly "n" times.
    Examples:

    	pattern		match count
    	\{,4}		0, 1, 2, 3 or 4
    	\{3,}		3, 4, 5, etc.
    	\{0,1}		0 or 1, same as \=
    	\{0,}		0 or more, same as *
    	\{1,}		1 or more, same as \+
    	\{3}		3

    MATCHING AS LITTLE AS POSSIBLE

    The items so far match as many characters as they can find.  To match as few
    as possible, use "\{-n,m}".  It works the same as "\{n,m}", except that the
    minimal amount possible is used.
       For example, use:

    	/ab\{-1,3}

    Will match "ab" in "abbb".  Actually, it will never match more than one b,
    because there is no reason to match more.  It requires something else to force
    it to match more than the lower limit.
       The same rules apply to removing "n" and "m".  It's even possible to remove
    both of the numbers, resulting in "\{-}".  This matches the item before it
    zero or more times, as few as possible.  The item by itself always matches
    zero times.  It is useful when combined with something else.  Example:

    	/a.\{-}b

    This matches "axb" in "axbxb".  If this pattern would be used:

    	/a.*b

    It would try to match as many characters as possible with ".*", thus it
    matches "axbxb" as a whole.

    *27.5*	Alternatives

    The "or" operator in a pattern is "\|".  Example:

    	/foo\|bar

    This matches "foo" or "bar".  More alternatives can be concatenated:

    	/one\|two\|three

    Matches "one", "two" and "three".
       To match multiple times, the whole thing must be placed in "\(" and "\)":

    	/\(foo\|bar\)\+

    This matches "foo", "foobar", "foofoo", "barfoobar", etc.
       Another example:

    	/end\(if\|while\|for\)

    This matches "endif", "endwhile" and "endfor".

    A related item is "\&".  This requires that both alternatives match in the
    same place.  The resulting match uses the last alternative.  Example:

    	/forever\&...

    This matches "for" in "forever".  It will not match "fortuin", for example.

    *27.6*	Character ranges

    To match "a", "b" or "c" you could use "/a\|b\|c".  When you want to match all
    letters from "a" to "z" this gets very long.  There is a shorter method:

    	/[a-z]

    The [] construct matches a single character.  Inside you specify which
    characters to match.  You can include a list of characters, like this:

    	/[0123456789abcdef]

    This will match any of the characters included.  For consecutive characters
    you can specify the range.  "0-3" stands for "0123".  "w-z" stands for "wxyz".
    Thus the same command as above can be shortened to:

    	/[0-9a-f]

    To match the "-" character itself make it the first or last one in the range.
    These special characters are accepted to make it easier to use them inside a
    [] range (they can actually be used anywhere in the search pattern):

    	\e	<Esc>
    	\t	<Tab>
    	\r	<CR>
    	\b	<BS>

    There are a few more special cases for [] ranges, see |/[]| for the whole
    story.

    COMPLEMENTED RANGE

    To avoid matching a specific character, use "^" at the start of the range.
    The [] item then matches everything but the characters included.  Example:

    	/"[^"]*"

    	 "	  a double quote
    	  [^"]	  any character that is not a double quote
    	      *	  as many as possible
    	       "  a double quote again

    This matches "foo" and "3!x", including the double quotes.

    PREDEFINED RANGES

    A number of ranges are used very often.  Vim provides a shortcut for these.
    For example:

    	/\a

    Finds alphabetic characters.  This is equal to using "/[a-zA-Z]".  Here are a
    few more of these:

    	item	matches			equivalent
    	\d	digit			[0-9]
    	\D	non-digit		[^0-9]
    	\x	hex digit		[0-9a-fA-F]
    	\X	non-hex digit		[^0-9a-fA-F]
    	\s	white space		[ 	]     (<Tab> and <Space>)
    	\S	non-white characters	[^ 	]     (not <Tab> and <Space>)
    	\l	lowercase alpha		[a-z]
    	\L	non-lowercase alpha	[^a-z]
    	\u	uppercase alpha		[A-Z]
    	\U	non-uppercase alpha	[^A-Z]

    	Note:
    	Using these predefined ranges works a lot faster than the character
    	range it stands for.
    	These items can not be used inside [].  Thus "[\d\l]" does NOT work to
    	match a digit or lowercase alpha.  Use "\(\d\|\l\)" instead.

    See |/\s| for the whole list of these ranges.

    *27.7*	Character classes

    The character range matches a fixed set of characters.  A character class is
    similar, but with an essential difference: The set of characters can be
    redefined without changing the search pattern.
       For example, search for this pattern:

    	/\f\+

    The "\f" items stands for file name characters.  Thus this matches a sequence
    of characters that can be a file name.
       Which characters can be part of a file name depends on the system you are
    using.  On MS-Windows, the backslash is included, on Unix it is not.  This is
    specified with the 'isfname' option.  The default value for Unix is:

    	:set isfname
    	isfname=@,48-57,/,.,-,_,+,,,#,$,%,~,=

    For other systems the default value is different.  Thus you can make a search
    pattern with "\f" to match a file name, and it will automatically adjust to
    the system you are using it on.

    	Note:
    	Actually, Unix allows using just about any character in a file name,
    	including white space.  Including these characters in 'isfname' would
    	be theoretically correct.  But it would make it impossible to find the
    	end of a file name in text.  Thus the default value of 'isfname' is a
    	compromise.

    The character classes are:

    	item	matches				option
    	\i	identifier characters		'isident'
    	\I	like \i, excluding digits
    	\k	keyword characters		'iskeyword'
    	\K	like \k, excluding digits
    	\p	printable characters		'isprint'
    	\P	like \p, excluding digits
    	\f	file name characters		'isfname'
    	\F	like \f, excluding digits

    *27.8*	Matching a line break

    Vim can find a pattern that includes a line break.  You need to specify where
    the line break happens, because all items mentioned so far don't match a line
    break.
       To check for a line break in a specific place, use the "\n" item:

    	/one\ntwo

    This will match at a line that ends in "one" and the next line starts with
    "two".  To match "one two" as well, you need to match a space or a line
    break.  The item to use for it is "\_s":

    	/one\_stwo

    To allow any amount of white space:

    	/one\_s\+two

    This also matches when "one  " is at the end of a line and "   two" at the
    start of the next one.

    "\s" matches white space, "\_s" matches white space or a line break.
    Similarly, "\a" matches an alphabetic character, and "\_a" matches an
    alphabetic character or a line break.  The other character classes and ranges
    can be modified in the same way by inserting a "_".

    Many other items can be made to match a line break by prepending "\_".  For
    example: "\_." matches any character or a line break.

    	Note:
    	"\_.*" matches everything until the end of the file.  Be careful with
    	this, it can make a search command very slow.

    Another example is "\_[]", a character range that includes a line break:

    	/"\_[^"]*"

    This finds a text in double quotes that may be split up in several lines.

    *27.9*	Examples

    Here are a few search patterns you might find useful.  This shows how the
    items mentioned above can be combined.

    FINDING A CALIFORNIA LICENSE PLATE

    A sample license plate number is "1MGU103".  It has one digit, three uppercase
    letters and three digits.  Directly putting this into a search pattern:

    	/\d\u\u\u\d\d\d

    Another way is to specify that there are three digits and letters with a
    count:

    	/\d\u\{3}\d\{3}

    Using [] ranges instead:

    	/[0-9][A-Z]\{3}[0-9]\{3}

    Which one of these you should use?  Whichever one you can remember.  The
    simple way you can remember is much faster than the fancy way that you can't.
    If you can remember them all, then avoid the last one, because it's both more
    typing and slower to execute.

    FINDING AN IDENTIFIER

    In C programs (and many other computer languages) an identifier starts with a
    letter and further consists of letters and digits.  Underscores can be used
    too.  This can be found with:

    	/\<\h\w*\>

    "\<" and "\>" are used to find only whole words.  "\h" stands for "[A-Za-z_]"
    and "\w" for "[0-9A-Za-z_]".

    	Note:
    	"\<" and "\>" depend on the 'iskeyword' option.  If it includes "-",
    	for example, then "ident-" is not matched.  In this situation use:

    		/\w\@<!\h\w*\w\@!

    	This checks if "\w" does not match before or after the identifier.
    	See |/\@<!| and |/\@!|.

    Next chapter: |usr_28|  Folding

    Copyright: see |manual-copyright|  vim:tw=78:ts=8:noet:ft=help:norl:

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