Regex Tutorial - \b Word Boundry in Regular Expression.

Tutorials

Regular-expression

Topic

What is Word Boundry?

Explanation

A word boundry is the boundry between a word character and a non-word character.The word characters are "[a-zA-Z0-9_]" all other characters are non word characters like the ",', etc. The length of word boundry is always "zero".

    string = "hiox india"
    "/\bhiox" - Match boundry between double quotes, the word "hiox".
    "/hiox\b" - Match boundry between the word "hiox", the space.

PHP Example:

    <?php
    $name = "sam paul christ dany";
    if (preg_match("/sam\b/", $name))
     echo "Pattern matches!";
    else 
     echo "Pattern not matched!";
    ?>

Result:

    Pattern matches!

In the above example the word "sam" and the space next to it is matched.

Perl Example:

    #! C:\programfiles\perl\bin\perl
    print "content-type: text/html\n\n";
    $name= "sam-paul-christ-dany";
    if ($name =~ m/sam\bpaul/) 
      {print "The name format matched!";} 
    else 
      {print "The name format not matched!";}

Result:

    The name format matched!

In the above example the pattern "sam\bpaul" does not match since the word boundry is found for the word "sam" and "-". so when matching other characters "paul" specify non word character "-" too as "sam\b-paul" in the pattern that should match.

Word Boundry "\b" metacharacter in Regular Expression.