Difference between w and b regular expression meta characters

Question

Can anyone explain the difference between  b and  w regular expression metacharacters  It is my understanding that both these metacharacters are used for word boundaries  Apart from this  which meta character is efficient for multilingual content

User · Accepted Answer

The metacharacter  b is an anchor like the caret and the dollar sign  It matches at a position that is called a  word boundary   This match is zero-length   There are three different positions that qualify as word boundaries    Before the first character in the string  if the first character is a word character  After the last character in the string  if the last character is a word character  Between two characters in the string  where one is a word character and the other is not a word character     Simply put   b allows you to perform a  whole words only  search using a regular expression in the form of  bword b  A  word character  is a character that can be used to form words  All characters that are not  word characters  are  non-word characters    In all flavors  the characters  a-zA-Z0-9   are word characters  These are also matched by the short-hand character class  w  Flavors showing  ascii  for word boundaries in the flavor comparison recognize only these as word characters    w stands for  word character   usually  A-Za-z0-9    Notice the inclusion of the underscore and digits    B is the negated version of  b   B matches at every position where  b does not  Effectively   B matches at any position between two word characters as well as at any position between two non-word characters    W is short for    w   the negated version of  w

User · Answer

w matches a word character   b is a zero-width match that matches a position character that has a word character on one side  and something that s not a word character on the other   Examples of things that aren t word characters include whitespace  beginning and end of the string  etc     w matches a  b  c  d  e  and f in  abc def   b matches the  zero-width  position before a  after c  before d  and after f in  abc def   See  http   www regular-expressions info reference html

User · Answer

w is not a word boundary  it matches any word character  including underscores   a-zA-Z0-9     b is a word boundary  that is  it matches the position between a word and a non-alphanumeric character   W or    w    These implementations may vary from language to language though

User · Answer

b  lt   this is a word boundary    Matches at a position that is followed by a word character but not preceded by a word character  or that is preceded by a word character but not followed by a word character    w  lt   stands for  word character      It always matches the ASCII characters  A-Za-z0-9    Is there anything specific you are trying to match   Some useful regex websites for beginners or just to wet your appetite    http   www regular-expressions info http   www javascriptkit com javatutors redev2 shtml http   www virtuosimedia com dev php 37-tested-php-perl-and-javascript-regular-expressions http   www i-programmer info programming javascript 4862-master-javascript-regular-expressions html   I found this to be a very useful book    Mastering Regular Expressions by Jeffrey E F  Friedl

User · Answer

Mahender  you probably meant the difference between  W  instead of  w  and  b  If not  then I would agree with  BoltClock and  jwismar above  Otherwise continue reading    W would match any non-word character and so its easy to try to use it to match word boundaries  The problem is that it will not match the start or end of a line   b is more suited for matching word boundaries as it will also match the start or end of a line  Roughly speaking  more experienced users can correct me here   b can be thought of as   W        Edit  as   mega mentions below   b is a zero-length match so   W      is not strictly correct  but hopefully helps explain the diff   Quick example  For the string Hello World     W would match Hello   with the space  but will not match World     b would match both Hello and World

[javascript] Difference between \w and \b regular expression meta characters

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