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Home: Perl Programming Help: Regular Expressions:
"qr/\d+.+\.pdf$/ );" what mean ?

 


tot94
Novice

Sep 17, 2015, 11:17 AM

Post #1 of 4 (17908 views)
"qr/\d+.+\.pdf$/ );" what mean ? Can't Post
Hello,

I'm new in perl ! I try to make a script to scrape my website. But, i want to perform myself with url regexion ! I found these one :

Code
my @links = $mech->find_all_links( url_regex => qr/\d+.+\.pdf$/ );
Code
 
What mean the expression ? 
I look on Internet, but do you know website in order to learn url regexion ? 
 
Thanks,


FishMonger
Veteran / Moderator

Sep 17, 2015, 11:29 AM

Post #2 of 4 (17905 views)
Re: [tot94] "qr/\d+.+\.pdf$/ );" what mean ? [In reply to] Can't Post
Code
The regular expression: 
 
(?-imsx:/\d+.+\.pdf$/) 
 
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): 
---------------------------------------------------------------------- 
  /                        '/' 
---------------------------------------------------------------------- 
  \d+                      digits (0-9) (1 or more times (matching 
                           the most amount possible)) 
---------------------------------------------------------------------- 
  .+                       any character except \n (1 or more times 
                           (matching the most amount possible)) 
---------------------------------------------------------------------- 
  \.                       '.' 
---------------------------------------------------------------------- 
  pdf                      'pdf' 
---------------------------------------------------------------------- 
  $                        before an optional \n, and the end of the 
                           string 
---------------------------------------------------------------------- 
  /                        '/' 
---------------------------------------------------------------------- 
)                        end of grouping 
----------------------------------------------------------------------


tot94
Novice

Sep 17, 2015, 11:47 AM

Post #3 of 4 (17903 views)
Re: [FishMonger] "qr/\d+.+\.pdf$/ );" what mean ? [In reply to] Can't Post
Thanks for your answer, so if i well understand, the delimiter is "/"?

So the expression is delimits here : / \d+.+\.pdf$ / .

What is the use of the secnd "\" ?

Wht the use of 'qr' ? Query ?

So this expression could catch a file like : 2a.pdf ?


Laurent_R
Veteran / Moderator

Sep 18, 2015, 2:42 AM

Post #4 of 4 (17895 views)
Re: [tot94] "qr/\d+.+\.pdf$/ );" what mean ? [In reply to] Can't Post
qr/.../ is the quote operator for regular expressions. It basically says: I am not passing an ordinary string, but a regex, and it says to the compiler to compile it as a regex.

In qr/\d+.+\.pdf$/ ), the first dot is a meta-character that will match any character (except a newline) and will do it any number of times (as any times as possible) because of the + quantifier that follows. The second dot is preceded by a backslash (the escape character), meaning that "\." is meant to match a literal dot ".".

And yes, this expression could catch a file like : 2a.pdf, or 2aa.pdf, 2abc.pdf, 3abdcef.pdf, etc.

 
 


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