정규식 편집하기

Regular Expression

정규표현 

定規表現 규칙이 정해진 표현

아래 내용은 위키피디아 내용을 단순 짜집기하였다.(https://ko.wikipedia.org/wiki/정규_표현식)

== Syntax ==

=== Delemiters ===
'/'를 사용하는 경우가 있다. 

=== Standards ===

==== POSIX basic and extended ====
{| class="wikitable"
!Metacharacter
!기능
!Description
|-
!<code>^</code>
|처음
|Matches the starting position within the string. In line-based tools, it matches the starting position of any line.
|-
!<code>.</code>
|문자
|Matches any single character (many applications exclude newlines, and exactly which characters are considered newlines is flavor-, character-encoding-, and platform-specific, but it is safe to assume that the line feed character is included). Within POSIX bracket expressions, the dot character matches a literal dot. For example, <code>a.c</code> matches "abc", etc., but <code>[a.c]</code> matches only "a", ".", or "c".
|-
!<code>[ ]</code>
|문자 클래스
|A bracket expression. Matches a single character that is contained within the brackets. For example, <code>[abc]</code> matches "a", "b", or "c". <code>[a-z]</code> specifies a range which matches any lowercase letter from "a" to "z". These forms can be mixed: <code>[abcx-z]</code> matches "a", "b", "c", "x", "y", or "z", as does <code>[a-cx-z]</code>.

The <code>-</code> character is treated as a literal character if it is the last or the first (after the <code>^</code>, if present) character within the brackets: <code>[abc-]</code>, <code>[-abc]</code>. Note that backslash escapes are not allowed. The <code>]</code> character can be included in a bracket expression if it is the first (after the <code>^</code>) character: <code>[]abc]</code>.
|-
!<code>[^ ]</code>
|부정
|Matches a single character that is not contained within the brackets. For example, <code>[^abc]</code> matches any character other than "a", "b", or "c". <code>[^a-z]</code> matches any single character that is not a lowercase letter from "a" to "z". Likewise, literal characters and ranges can be mixed.
|-
!<code>$</code>
|끝
|Matches the ending position of the string or the position just before a string-ending newline. In line-based tools, it matches the ending position of any line.
|-
!<code>( )</code>
|하위식
|Defines a marked subexpression. The string matched within the parentheses can be recalled later (see the next entry, <code>\''n''</code>). A marked subexpression is also called a block or capturing group. '''BRE mode requires <code>\( \)</code>'''.
|-
!<code>\''n''</code>
|일치하는 n번째 패턴
|Matches what the ''n''th marked subexpression matched, where ''n'' is a digit from 1 to 9. This construct is vaguely defined in the POSIX.2 standard. Some tools allow referencing more than nine capturing groups. Also known as a backreference.
|-
!<code>*</code>
|0회 이상
|Matches the preceding element zero or more times. For example, <code>ab*c</code> matches "ac", "abc", "abbbc", etc. <code>[xyz]*</code> matches "", "x", "y", "z", "zx", "zyx", "xyzzy", and so on. <code>(ab)*</code> matches "", "ab", "abab", "ababab", and so on.
|-
!<code>{''m'',''n''}</code>
|m회 이상 n회 이하
|Matches the preceding element at least ''m'' and not more than ''n'' times. For example, <code>a{3,5}</code> matches only "aaa", "aaaa", and "aaaaa". This is not found in a few older instances of regexes. '''BRE mode requires <code>\{''m'',''n''\}</code>'''.
|}

==== POSIX extended ====
{| class="wikitable"
!Metacharacter
!기능
!Description
|-
!<code>?</code>
!0 또는 1회
|Matches the preceding element zero or one time. For example, <code>ab?c</code> matches only "ac" or "abc".
|-
!<code>+</code>
!1회 이상
|Matches the preceding element one or more times. For example, <code>ab+c</code> matches "abc", "abbc", "abbbc", and so on, but not "ac".
|-
!<code><nowiki>|</nowiki></code>
!선택
|The choice (also known as alternation or set union) operator matches either the expression before or the expression after the operator. For example, <code><nowiki>abc|def</nowiki></code> matches "abc" or "def".
|}

==== Character classes ====
{| class="wikitable sortable"
!POSIX
!Non-standard
!Perl/Tcl
!Vim
!Java
!ASCII
!Description
|-
|
|<code>[:ascii:]</code>
|
|
|<code>\p{ASCII}</code>
|<code>[\x00-\x7F]</code>
|ASCII characters
|-
|<code>[:alnum:]</code>
|
|
|
|<code>\p{Alnum}</code>
|<code>[A-Za-z0-9]</code>
|Alphanumeric characters
|-
|
|<code>[:word:]</code>
|<code>\w</code>
|<code>\w</code>
|<code>\w</code>
|<code>[A-Za-z0-9_]</code>
|Alphanumeric characters plus "_"
|-
|
|
|<code>\W</code>
|<code>\W</code>
|<code>\W</code>
|<code>[^A-Za-z0-9_]</code>
|Non-word characters
|-
|<code>[:alpha:]</code>
|
|
|<code>\a</code>
|<code>\p{Alpha}</code>
|<code>[A-Za-z]</code>
|Alphabetic characters
|-
|<code>[:blank:]</code>
|
|
|<code>\s</code>
|<code>\p{Blank}</code>
|<code>[ \t]</code>
|Space and tab
|-
|
|
|<code>\b</code>
|<code>\< \></code>
|<code>\b</code>
|<code><nowiki>(?<=\W)(?=\w)|(?<=\w)(?=\W)</nowiki></code>
|Word boundaries
|-
|
|
|
|
|<code>\B</code>
|<code><nowiki>(?<=\W)(?=\W)|(?<=\w)(?=\w)</nowiki></code>
|Non-word boundaries
|-
|<code>[:cntrl:]</code>
|
|
|
|<code>\p{Cntrl}</code>
|<code>[\x00-\x1F\x7F]</code>
|Control characters
|-
|<code>[:digit:]</code>
|
|<code>\d</code>
|<code>\d</code>
|<code>\p{Digit}</code> or <code>\d</code>
|<code>[0-9]</code>
|Digits
|-
|
|
|<code>\D</code>
|<code>\D</code>
|<code>\D</code>
|<code>[^0-9]</code>
|Non-digits
|-
|<code>[:graph:]</code>
|
|
|
|<code>\p{Graph}</code>
|<code>[\x21-\x7E]</code>
|Visible characters
|-
|<code>[:lower:]</code>
|
|
|<code>\l</code>
|<code>\p{Lower}</code>
|<code>[a-z]</code>
|Lowercase letters
|-
|<code>[:print:]</code>
|
|
|<code>\p</code>
|<code>\p{Print}</code>
|<code>[\x20-\x7E]</code>
|Visible characters and the space character
|-
|<code>[:punct:]</code>
|
|
|
|<code>\p{Punct}</code>
|<code><nowiki>[][!"#$%&'()*+,./:;<=>?@\^_`{|}~-]</nowiki></code>
|Punctuation characters
|-
|<code>[:space:]</code>
|
|<code>\s</code>
|<code>\_s</code>
|<code>\p{Space}</code> or <code>\s</code>
|<code>[ \t\r\n\v\f]</code>
|Whitespace characters
|-
|
|
|<code>\S</code>
|<code>\S</code>
|<code>\S</code>
|<code>[^ \t\r\n\v\f]</code>
|Non-whitespace characters
|-
|<code>[:upper:]</code>
|
|
|<code>\u</code>
|<code>\p{Upper}</code>
|<code>[A-Z]</code>
|Uppercase letters
|-
|<code>[:xdigit:]</code>
|
|
|<code>\x</code>
|<code>\p{XDigit}</code>
|<code>[A-Fa-f0-9]</code>
|Hexadecimal digits
|}

== Examples ==
   메타문자 ;; 메타문자들의 열은 표현할 정규식을 지정한다.
    =~ m//  ;; 펄에서 문자열을 '일치'시키려는 동작을 지정한다.
    =~ s/// ;; 펄에서 문자열을 '대체'시키려는 동작을 지정한다.
{| class="wikitable"
!Metacharacter(s)
!Description
!Example
|-
!<code>.</code>
|Normally matches any character except a newline.

Within square brackets the dot is literal.
|
 $string1 = "Hello World\n";
 if ($string1 =~ m/...../) {
   print "$string1 has length >= 5.\n";
 }
'''Output:'''
 Hello World
  has length >= 5.
|-
!<code>( )</code>
|Groups a series of pattern elements to a single element.

When you match a pattern within parentheses, you can use any of <code>$1</code>, <code>$2</code>, ... later to refer to the previously matched pattern.
|
 $string1 = "Hello World\n";
 if ($string1 =~ m/(H..).(o..)/) {
   print "We matched '$1' and '$2'.\n";
 }
'''Output:'''
 We matched 'Hel' and 'o W'.
|-
!<code>+</code>
|Matches the preceding pattern element one or more times.
|
 $string1 = "Hello World\n";
 if ($string1 =~ m/l+/) {
   print "There are one or more consecutive letter \"l\"'s in $string1.\n";
 }
'''Output:'''
 There are one or more consecutive letter "l"'s in Hello World.
|-
!<code>?</code>
|Matches the preceding pattern element zero or one time.
|
 $string1 = "Hello World\n";
 if ($string1 =~ m/H.?e/) {
   print "There is an 'H' and a 'e' separated by ";
   print "0-1 characters (e.g., He Hue Hee).\n";
 }
'''Output:'''
 There is an 'H' and a 'e' separated by 0-1 characters (e.g., He Hue Hee).
|-
!<code>?</code>
|Modifies the <code>*</code>, <code>+</code>, <code>?</code> or <code>{M,N}</code>'d regex that comes before to match as few times as possible.
|
 $string1 = "Hello World\n";
 if ($string1 =~ m/(l.+?o)/) {
   print "The non-greedy match with 'l' followed by one or ";
   print "more characters is 'llo' rather than 'llo Wo'.\n";
 }
'''Output:'''
 The non-greedy match with 'l' followed by one or more characters is 'llo' rather than 'llo Wo'.
|-
!<code>*</code>
|Matches the preceding pattern element zero or more times.
|
 $string1 = "Hello World\n";
 if ($string1 =~ m/el*o/) {
   print "There is an 'e' followed by zero to many ";
   print "'l' followed by 'o' (e.g., eo, elo, ello, elllo).\n";
 }
'''Output:'''
 There is an 'e' followed by zero to many 'l' followed by 'o' (e.g., eo, elo, ello, elllo).
|-
!<code>{M,N}</code>
|Denotes the minimum M and the maximum N match count.

N can be omitted and M can be 0: <code>{M}</code> matches "exactly" M times; <code>{M,}</code> matches "at least" M times; <code>{0,N}</code> matches "at most" N times.

<code>x* y+ z?</code> is thus equivalent to <code>x{0,} y{1,} z{0,1}</code>.
|
 $string1 = "Hello World\n";
 if ($string1 =~ m/l{1,2}/) {
   print "There exists a substring with at least 1 ";
   print "and at most 2 l's in $string1\n";
 }
'''Output:'''
 There exists a substring with at least 1 and at most 2 l's in Hello World
|-
!<code>[…]</code>
|Denotes a set of possible character matches.
|
 $string1 = "Hello World\n";
 if ($string1 =~ m/[aeiou]+/) {
   print "$string1 contains one or more vowels.\n";
 }
'''Output:'''
 Hello World
  contains one or more vowels.
|-
!<code><nowiki>|</nowiki></code>
|Separates alternate possibilities.
|
 $string1 = "Hello World\n";
 if ($string1 =~ m/(Hello|Hi|Pogo)/) {
   print "$string1 contains at least one of Hello, Hi, or Pogo.";
 }
'''Output:'''
 Hello World
  contains at least one of Hello, Hi, or Pogo.
|-
!<code>\b</code>
|Matches a zero-width boundary between a word-class character (see next) and either a non-word class character or an edge; same as

<code>(^\w|\w$|\W\w|\w\W)</code>.
|
 $string1 = "Hello World\n";
 if ($string1 =~ m/llo\b/) {
   print "There is a word that ends with 'llo'.\n";
 }
'''Output:'''
 There is a word that ends with 'llo'.
|-
!<code>\w</code>
|Matches an alphanumeric character, including "_";

same as <code>[A-Za-z0-9_]</code> in ASCII, and

: <code>[\p{Alphabetic}\p{GC=Mark}\p{GC=Decimal_Number}\p{GC=Connector_Punctuation}]</code>

in Unicode, where the <code>Alphabetic</code> property contains more than Latin letters, and the <code>Decimal_Number</code> property contains more than Arab digits.
|
 $string1 = "Hello World\n";
 if ($string1 =~ m/\w/) {
   print "There is at least one alphanumeric ";
   print "character in $string1 (A-Z, a-z, 0-9, _).\n";
 }
'''Output:'''
 There is at least one alphanumeric character in Hello World
  (A-Z, a-z, 0-9, _).
|-
!<code>\W</code>
|Matches a ''non''-alphanumeric character, excluding "_";

same as <code>[^A-Za-z0-9_]</code> in ASCII, and

: <code>[^\p{Alphabetic}\p{GC=Mark}\p{GC=Decimal_Number}\p{GC=Connector_Punctuation}]</code>

in Unicode.
|
 $string1 = "Hello World\n";
 if ($string1 =~ m/\W/) {
   print "The space between Hello and ";
   print "World is not alphanumeric.\n";
 }
'''Output:'''
 The space between Hello and World is not alphanumeric.
|-
!<code>\s</code>
|Matches a whitespace character,

which in ASCII are tab, line feed, form feed, carriage return, and space;

in Unicode, also matches no-break spaces, next line, and the variable-width spaces (amongst others).
|
 $string1 = "Hello World\n";
 if ($string1 =~ m/\s.*\s/) {
   print "In $string1 there are TWO whitespace characters, which may";
   print " be separated by other characters.\n";
 }
'''Output:'''
 In Hello World
  there are TWO whitespace characters, which may be separated by other characters.
|-
!<code>\S</code>
|Matches anything ''but'' a whitespace.
|
 $string1 = "Hello World\n";
 if ($string1 =~ m/\S.*\S/) {
   print "In $string1 there are TWO non-whitespace characters, which";
   print " may be separated by other characters.\n";
 }
'''Output:'''
 In Hello World
  there are TWO non-whitespace characters, which may be separated by other characters.
|-
!<code>\d</code>
|Matches a digit;

same as <code>[0-9]</code> in ASCII;

in Unicode, same as the <code>\p{Digit}</code> or <code>\p{GC=Decimal_Number}</code> property, which itself the same as the <code>\p{Numeric_Type=Decimal}</code> property.
|
 $string1 = "99 bottles of beer on the wall.";
 if ($string1 =~ m/(\d+)/) {
   print "$1 is the first number in '$string1'\n";
 }
'''Output:'''
 99 is the first number in '99 bottles of beer on the wall.'
|-
!<code>\D</code>
|Matches a non-digit;

same as <code>[^0-9]</code> in ASCII or <code>\P{Digit}</code> in Unicode.
|
 $string1 = "Hello World\n";
 if ($string1 =~ m/\D/) {
   print "There is at least one character in $string1";
   print " that is not a digit.\n";
 }
'''Output:'''
 There is at least one character in Hello World
  that is not a digit.
|-
!<code>^</code>
|Matches the beginning of a line or string.
|
 $string1 = "Hello World\n";
 if ($string1 =~ m/^He/) {
   print "$string1 starts with the characters 'He'.\n";
 }
'''Output:'''
 Hello World
  starts with the characters 'He'.
|-
!<code>$</code>
|Matches the end of a line or string.
|
 $string1 = "Hello World\n";
 if ($string1 =~ m/rld$/) {
   print "$string1 is a line or string ";
   print "that ends with 'rld'.\n";
 }
'''Output:'''
 Hello World
  is a line or string that ends with 'rld'.
|-
!<code>\A</code>
|Matches the beginning of a string (but not an internal line).
|
 $string1 = "Hello\nWorld\n";
 if ($string1 =~ m/\AH/) {
   print "$string1 is a string ";
   print "that starts with 'H'.\n";
 }
'''Output:'''
 Hello
 World
  is a string that starts with 'H'.
|-
!<code>\z</code>
|Matches the end of a string (but not an internal line).
|
 $string1 = "Hello\nWorld\n";
 if ($string1 =~ m/d\n\z/) {
   print "$string1 is a string ";
   print "that ends with 'd\\n'.\n";
 }
'''Output:'''
 Hello
 World
  is a string that ends with 'd\n'.
|-
!<code>[^…]</code>
|Matches every character except the ones inside brackets.
|
 $string1 = "Hello World\n";
 if ($string1 =~ m/[^abc]/) {
  print "$string1 contains a character other than ";
  print "a, b, and c.\n";
 }
'''Output:'''
 Hello World
  contains a character other than a, b, and c.
|}

== 외부링크 ==
https://regexr.com/
[[분류:프로그래밍]]