KarthikK has asked for the wisdom of the Perl Monks concerning the following question:

I need help in regular expressions. I have a field where user could type in a config spec/some free text/Links (Http or FTP or file share)
i have to perform a check if the config spec is valid (as per rule specified)

- User should not specify config spec with /main/latest or \main\latest

- User should not specify config spec with version numbers with @@ ex: foo.c@@\main\4

- User could specify /main/latest or \main\latest or @@\main only if it has the following text:
element -dir \vob\folder@@\main\1
element -directory \vob\folder@@\main\1
element -directory \vob\folder\main\1
element -dir \vob\folder\main\1

- Below are some valid rules
element * label
element -file filename LABEL
if the user enter
element -file filename

without LABEL i should trap these. Here LABLES are some text which do not contain (/main/ or \main\ or /main/latest or \main\latest or @@)

I want to have these patterns in a place something like the ini file so that it could be configured.

Is there a way to get a pattern for these scenarois?

thanks a lot in advance

Regards
KK

Replies are listed 'Best First'.
Re: Help with regular expressions
by moritz (Cardinal) on Aug 29, 2008 at 11:43 UTC
    Your description and examples aren't enough to to deduce a regex from them. You should try to define precisely what you want to allow or not. This could look like that: 
    A valid ref spec is a string that starts 
with the literal 'element ', and is followed by

* Either a star '*' OR by m/-dir(ectory)? \S+/
                    OR by m/-file \S+/
* then by a label

A label is ...

    [download]

    Once you know what you actually want to match, you can translate that into a regex quite easily: 

    my $re = qr{
   element \s
      (
        \*
      | -dir(ectory)? \S+
      | -file \S+
      )
   # Label:
   \w+
}x;

    [download]

    You should also handle special cases special, ie don't try to munge them into your regex, but rather make an extra path to check for special cases.

[reply]
[d/l]
[select]
      thx for your suggestions. Perhaps i will try to explain more. Basically since this is a free text field user would typein Configspec or some notes. the only way i could find that the text is a config spec is by finiding the text "element". But there are riles which i had mentioned in my post. Ofcourse i dont want to validate these lables with ClearCase. This is lets say a soft verification of the config spec. I hope i am clear
[reply]
Re: Help with regular expressions
by apl (Monsignor) on Aug 29, 2008 at 11:41 UTC
[reply]

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