Pattern

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Patterns and search commands
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

/ /{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. v_star-default In Visual mode, search forward for the current selection. default-mappings
# # 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). v_#-default In Visual mode, search backward for the current selection. default-mappings
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. 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, you get a normal message "Pattern not found", 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 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. E1281 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
/\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
/\%^ 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 E1204 \%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. There can only be ten of these. You can use "\%(" to add more, but not counting it as a sub-expression. 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 E76 \_[] 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]".
/\%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 [email protected] 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-matching

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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