Re: Understanding Regex

they are infact different: when playing with regexes i always suggest two tools and the use of YAPE::Regex::Explain



perl -MYAPE::Regex::Explain -e " print YAPE::Regex::Explain->new(qr/$A
+RGV[0]/)->explain();" ^\s*[^\s\*=]+\s*=
The regular expression:

(?-imsx:\s*[\s\*=]+\s*=)

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):
----------------------------------------------------------------------
  \s*                      whitespace (\n, \r, \t, \f, and " ") (0 or
                           more times (matching the most amount
                           possible))
----------------------------------------------------------------------
  [\s\*=]+                 any character of: whitespace (\n, \r, \t,
                           \f, and " "), '\*', '=' (1 or more times
                           (matching the most amount possible))
----------------------------------------------------------------------
  \s*                      whitespace (\n, \r, \t, \f, and " ") (0 or
                           more times (matching the most amount
                           possible))
----------------------------------------------------------------------
  =                        '='
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------


perl -MYAPE::Regex::Explain -e " print YAPE::Regex::Explain->new(qr/$A
+RGV[0]/)->explain();" ^\s*\w+\s*=
The regular expression:

(?-imsx:\s*\w+\s*=)

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):
----------------------------------------------------------------------
  \s*                      whitespace (\n, \r, \t, \f, and " ") (0 or
                           more times (matching the most amount
                           possible))
----------------------------------------------------------------------
  \w+                      word characters (a-z, A-Z, 0-9, _) (1 or
                           more times (matching the most amount
                           possible))
----------------------------------------------------------------------
  \s*                      whitespace (\n, \r, \t, \f, and " ") (0 or
                           more times (matching the most amount
                           possible))
----------------------------------------------------------------------
  =                        '='
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------
[download]

HtH
L*
UPDATE: see the wise advice from Lotus1 and my next post: ^ was vaporized by the command line processor.

L*

There are no rules, there are no thumbs..
Reinvent the wheel, then learn The Wheel; may be one day you reinvent one of THE WHEELS.

Comment on Re: Understanding Regex Select or Download Code

Replies are listed 'Best First'.
Re^2: Understanding Regex by Lotus1 (Vicar) on Nov 18, 2015 at 16:19 UTC
It looks like you missed the caret, '^', inside the character group when you ran the explain function the first time. It should be `any character except: whitespace...`	[reply] [d/l]
Re^3: Understanding Regex by Discipulus (Canon) on Nov 19, 2015 at 07:54 UTC
good spotted an thanks Lotus1 was just partially my fault: the code was correct but, as i work on an unfriendly OS, i need to put double quotes around the argument. So the actual command line became: `perl -MYAPE::Regex::Explain -e " print YAPE::Regex::Explain->new(qr/$A +RGV[0]/)->explain();" "^\s[^\s\=]+\s="` [download] with the right output: Read more... (2 kB) and the second one `perl -MYAPE::Regex::Explain -e " print YAPE::Regex::Explain->new(qr/$ARGV[0]/)->explain();" "^\s\w+\s="` with his right output: Read more... (2 kB) For the OP the best was probably to highlight only the different part: perl -MYAPE::Regex::Explain -e " print YAPE::Regex::Explain->new(qr/$A +RGV[0]/)->explain();" "[^\s\=]" .. ---------------------------------------------------------------------- [^\s\=] any character except: whitespace (\n, \r, \t, \f, and " "), '\', '=' ---------------------------------------------------------------------- perl -MYAPE::Regex::Explain -e " print YAPE::Regex::Explain->new(qr/$A +RGV[0]/)->explain();" "\w" .. ---------------------------------------------------------------------- \w word characters (a-z, A-Z, 0-9, _) ---------------------------------------------------------------------- [download] L* There are no rules, there are no thumbs.. Reinvent the wheel, then learn The Wheel; may be one day you reinvent one of THE WHEELS.	[reply] [d/l] [select]