in reply to Regex: Capturing and optionally replacing

Forget about doing everything in one regexp. It just makes it hard to read and hard to maintain. 

while (<DATA>) {
   chomp;
   my ($host, $domain, $test) = /^([^,]+),([^.]+)\.(.+)$/;
   next if not defined $host;
   $domain =~ s/,/./g;
   next if substr($domain, -4) eq '.net';
   print("Host: $host   Test: $test\n");
}

[download]

Update: This should be faster: 

while (<DATA>) {
   print("Host: $1   Test: $2\n")
      if /^([^,]+),[^.]+(?<!,net)\.(.+)$/;
}

[download]

Update: I just realized you said it needs to process 6000 files a minute. That's 100 files a second! That seems excessive. You way want to rethink your design.

Replies are listed 'Best First'.
Re^2: Regex: Capturing and optionally replacing
by McDarren (Abbot) on Dec 08, 2005 at 16:11 UTC
    Oh, okay... fair enough.

    But just to clarify... this is the output I am currently getting: 

    Host:hosta-sel-kr-1 Test:testa
Host:hostb-sel-kr-1 Test:testb
Host:hostc-sel-kr-1,my-domain,com Test:testa
Host:hostd-sel-kr-1,my-domain,com Test:testc
Host:hoste-sel-kr-1 Test:testxyz
Host:hosta-mel-au-1 Test:testabc
Host:hosta-mel-au-1 Test:testdef
Host:hostxyz Test:testabc
Host:someotherhost Test:someothertest

    [download]
    and this is the output I want: 
    Host:hosta-sel-kr-1 Test:testa
Host:hostb-sel-kr-1 Test:testb
Host:hostc-sel-kr-1.my-domain.com Test:testa
Host:hostd-sel-kr-1.my-domain.com Test:testc
Host:hoste-sel-kr-1 Test:testxyz
Host:hosta-mel-au-1 Test:testabc
Host:hosta-mel-au-1 Test:testdef
Host:hostxyz Test:testabc
Host:someotherhost Test:someothertest

    [download]
    (Notice that the only difference is that the commas in the com domain names have been replaced with periods)

    So your solution doesn't actually give the desired result.

[reply]
[d/l]
[select]

      Based on the variable name, I thought you were only printing the host without the domain.

      And when you said "skip it", I thought you meant the line, not the domain. 

      while (<DATA>) {
   my ($host, $domain, $test) = /^([^,.]+)(,[^.]+|)\.(.+)$/;
   $domain =~ s/,/./g;
   $domain = '' if /\.net$/;
   print("Host:$host$domain Test:$test\n");
}

      [download]

      Turns out

      $domain =~ s/^.*\.net$//;
      takes the same amout of time as
      $domain = '' if substr($domain, -4) eq '.net';
      but both are slightly slower than
      $domain = '' if /\.net$/;

      Update: 17% faster: 

      while (<DATA>) {
   chomp;
   my ($host, $test) = split(/\./, $_, 2);
   $host =~ s/,/./g;
   $host =~ s/\..*\.net$//;
   print("Host:$host Test:$test\n");
}

      [download]

      Update: If I change
      $host =~ s/\..*\.net$//;
      to
      $host =~ s/\.my-domain\.net$//;
      my version is 6% faster than yours (with $host =~ s/,/./g; added).

      Update: Benchmark code

      Read more... (2 kB)
[reply]
[d/l]
[select]
        Great, thanks for that :)

        I guess the lesson I've learned here is to never forget the kiss principle ;)

        Cheers,
        Darren :)

[reply]
        Okay... this one kept me awake last night :(

        Because I'd still like to know... how could I have re-written the original expression to get rid of the unwanted commas?

        Can somebody please put me out of my misery?
        (I promise I won't use it in production :D)

[reply]

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