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regular expression '([\w]+)';

Posted on 2015-02-08
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Hi Experts,

I'm updating a JMeter script and trying to understand some of the regular expressions which are now failing. Three examples are '([\w]+)'; and ([\w]+); and "([\w]+)";
Can anyone please explain the above expressions and provide an example of what they would capture

Thanks

Gavin
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Question by:victoriaharry
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Accepted Solution

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ozo earned 500 total points
ID: 40597520
perl -MYAPE::Regex::Explain -e print YAPE::Regex::Explain->new($_)->explain for qr/'([\w]+)';/, qr/([\w]+);/, qr/"([\w]+)";/
The regular expression:

(?-imsx:'([\w]+)';)

matches as follows:
 
NODE                     EXPLANATION
----------------------------------------------------------------------
(?-imsx:                 group, but do not capture (case-sensitive)
                         (with ^ and $ matching normally) (with . not
                         matching \n) (matching whitespace and #
                         normally):
----------------------------------------------------------------------
  '                        '\''
----------------------------------------------------------------------
  (                        group and capture to \1:
----------------------------------------------------------------------
    [\w]+                    any character of: word characters (a-z,
                             A-Z, 0-9, _) (1 or more times (matching
                             the most amount possible))
----------------------------------------------------------------------
  )                        end of \1
----------------------------------------------------------------------
  ';                       '\';'
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------
The regular expression:

(?-imsx:([\w]+);)

matches as follows:
 
NODE                     EXPLANATION
----------------------------------------------------------------------
(?-imsx:                 group, but do not capture (case-sensitive)
                         (with ^ and $ matching normally) (with . not
                         matching \n) (matching whitespace and #
                         normally):
----------------------------------------------------------------------
  (                        group and capture to \1:
----------------------------------------------------------------------
    [\w]+                    any character of: word characters (a-z,
                             A-Z, 0-9, _) (1 or more times (matching
                             the most amount possible))
----------------------------------------------------------------------
  )                        end of \1
----------------------------------------------------------------------
  ;                        ';'
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------
The regular expression:

(?-imsx:"([\w]+)";)

matches as follows:
 
NODE                     EXPLANATION
----------------------------------------------------------------------
(?-imsx:                 group, but do not capture (case-sensitive)
                         (with ^ and $ matching normally) (with . not
                         matching \n) (matching whitespace and #
                         normally):
----------------------------------------------------------------------
  "                        '"'
----------------------------------------------------------------------
  (                        group and capture to \1:
----------------------------------------------------------------------
    [\w]+                    any character of: word characters (a-z,
                             A-Z, 0-9, _) (1 or more times (matching
                             the most amount possible))
----------------------------------------------------------------------
  )                        end of \1
----------------------------------------------------------------------
  ";                       '";'
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------





print "$_ captures ", q{ 'this';  that;  "the_other"; } =~ $_, "\n" for qw{ '([\w]+)'; ([\w]+); "([\w]+)"; }                    
'([\w]+)'; captures this
([\w]+); captures that
"([\w]+)"; captures the_other
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LVL 84

Expert Comment

by:ozo
ID: 40597533
By the way, each of those would do exactly the same thing without the [] around the \w
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