Greetings fellow monks

 I have a problem of efficiency in a little tool I'm writing.

 Essentially I have two arrays, one containing lines from a logfile, as produced by syslog, and one containing regular expressions.

 I wish to remove from the loglines array all lines which match any of the regular expressions in my list.

 My current code looks like this:

my @REGEXPS = ( 
   "^\w{3} [ :0-9]{11} [._[:alnum:]-]+ pppd\[[0-9]+\]: (sent|rcvd) \[L
+CP EchoReq id=[[:alnum:]]+ magic=[ [:alnum:]]+\]$",
   "^\w{3} [ :0-9]{11} [._[:alnum:]-]+ ssh\(pam_[[:alnum:]]+\)\[[0-9]+
+\]: session opened for user [[:alnum:]-]+ by \(uid=[0-9]+\)$",
     );

my @KEEP = ();

foreach my $line ( @SYSLOG )
{
    my $match = 0;

    foreach my $r ( @REGEXPS )
    {    
       if ( $line =~ /$r/)
       { 
          $match = 1;
       }
    }

    if (! $match )
    {
    push @KEEP, $line;
    }
}

[download]

 This is slow, because I'm testing each regular expression against each line, making the number of matchs N x N.

 What are my alternatives?

 I've considered moving the lines into a hash instead, and using delete upon them - but I'm not sure how much of a gain this would be.

 I can't help thinking I should be using map, or grep for this - but I'm not entirely sure how to do this.

 (Yes this is replicating the functionality of the logcheck tool - it's a prototype rewrite in perl I'm producing).

Steve
---
steve.org.uk

In reply to Removing all lines from an array which match against a second array by skx

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