Still celebrating National IT Professionals Day with 3 months of free Premium Membership. Use Code ITDAY17

x
?
Solved

A doubt in regex

Posted on 2011-09-07
16
Medium Priority
?
301 Views
Last Modified: 2012-05-12
my requirement:
 $archive =~ /Merry\.Rolls\.(GR\d+\.\d+.\d+)\.(\w+).tgz/;

$archive can be:
Merry.Rolls.SR2.1.0.07Sep11_082115.tgz
OR
Merry.Rolls.GR2.1.0.07Sep11_082115.D.tgz

The second one fails. What shpuld be my regex?
The D in the second one can be any other letter.
0
Comment
Question by:pvinodp
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 5
  • 4
  • 3
  • +3
16 Comments
 
LVL 23

Expert Comment

by:Kamaraj Subramanian
ID: 36494772
$archive =~ /Merry\.Rolls\.([GS]R\d+\.\d+.\d+)\.(\w+).tgz/;

Open in new window

0
 

Author Comment

by:pvinodp
ID: 36494795
Sorry that was a typo:
$archive can be:
Merry.Rolls.GR2.1.0.07Sep11_082115.tgz
OR
Merry.Rolls.GR2.1.0.07Sep11_082115.D.tgz
0
 

Author Comment

by:pvinodp
ID: 36494807
basically what i want is how to write a regex which could either be \w followed by a . or nothing..

ie:
mytext.D.tgz OR mytext.tgz
0
Survive A High-Traffic Event with Percona

Your application or website rely on your database to deliver information about products and services to your customers. You can’t afford to have your database lose performance, lose availability or become unresponsive – even for just a few minutes.

 
LVL 84

Accepted Solution

by:
ozo earned 800 total points
ID: 36494822
/Merry\.Rolls\.(GR\d+\.\d+.\d+)\.(\w+(?:\.D)?).tgz/;
0
 

Author Comment

by:pvinodp
ID: 36494914
what is the meaning of (?:\D)?  
0
 
LVL 75

Assisted Solution

by:käµfm³d 👽
käµfm³d   👽 earned 600 total points
ID: 36495196
(?:\D)
That means:

(?: ... )    Non-capturing group
\D           Any character NOT a digit

Open in new window


However, ozo's pattern is actually:

(?:\.D)

Open in new window


which means:

(?: ... )    Non-capturing group
\.           Literal period
D            Literal "D"

Open in new window


Notice the difference a character can make! The question mark following the non-capturing group makes the whole group optional (i.e. 0 or 1 occurrences).
0
 
LVL 63

Assisted Solution

by:Zvonko
Zvonko earned 400 total points
ID: 36497873
Check this:
$archive =~ /Merry\.Rolls\.(GR\d+\.\d+.\d+)\.(\w+)(\.D)?.tgz/;

Open in new window

That will allow optional .D
0
 
LVL 75

Expert Comment

by:käµfm³d 👽
ID: 36498217
@Zvonko
That is identical to what ozo already posted ( http:#36494822 ), save a difference in grouping. There is no functional difference between your pattern and ozo's pattern   : \
0
 
LVL 63

Expert Comment

by:Zvonko
ID: 36498353
I see a difference.
0
 
LVL 75

Expert Comment

by:käµfm³d 👽
ID: 36498752
How enlightening...
0
 
LVL 63

Expert Comment

by:Zvonko
ID: 36498819
Sorry, I withdrow my comment http:#36497873

I posted it mainly to show how the lookahead pattern can be avoided.

But first of all Perl understands lookahead and second I just tested it also in IE browser and now even IE understands lookahead patterns in RegExp Objects.
So there is no reason for avoiding it.


0
 
LVL 75

Expert Comment

by:käµfm³d 👽
ID: 36498863
Where do you see a lookahead?
0
 
LVL 84

Expert Comment

by:ozo
ID: 36498886
the original question does not specify what captures are desired in the case of Merry.Rolls.GR2.1.0.07Sep11_082115.D.tgz
it may be that
/Merry\.Rolls\.(GR\d+\.\d+.\d+)\.(\w+)(\.D)?.tgz/
would be preferable
0
 
LVL 35

Assisted Solution

by:Terry Woods
Terry Woods earned 200 total points
ID: 36500478
Zvonko, I think you confused the ?: in (?:\.D)? for a lookahead. Actually, the ?: just makes the group into a non-capturing group.
0
 
LVL 75

Expert Comment

by:käµfm³d 👽
ID: 36502369
Awww...   Terry, you spoiled the surprise  8-P
0
 

Author Closing Comment

by:pvinodp
ID: 36535576
thanks all
0

Featured Post

Independent Software Vendors: We Want Your Opinion

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Whatever be the reason, if you are working on web development side,  you will need day-today validation codes like email validation, date validation , IP address validation, phone validation on any of the edit page or say at the time of registration…
Fine Tune your automatic Updates for Ubuntu / Debian
Learn how to navigate the file tree with the shell. Use pwd to print the current working directory: Use ls to list a directory's contents: Use cd to change to a new directory: Use wildcards instead of typing out long directory names: Use ../ to move…
Explain concepts important to validation of email addresses with regular expressions. Applies to most languages/tools that uses regular expressions. Consider email address RFCs: Look at HTML5 form input element (with type=email) regex pattern: T…
Suggested Courses

715 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question