如何在Perl中使用正则表达式来处理文本

Question

How do you take a part a line in a text file which will be used to reformat the way the file should look?

so for example in my text of:

Dec 27 21:49:41 osboxes NetworkManager[686]: <info>    nameserver '192.168.221.2'

The regex that I made would match the the text

  /([a-z][a-z][a-z]\s(\d\d)\s(\d\d):(\d\d):(\d\d)\s[a-z]*\s(NetworkManager).*)/ig

but how do you make it so that the output will be different, basically rearranging so that it would look something like this

**NetworkManager** osboxes Dec 27 21:49:41 <info>    nameserver '192.168.221.2'. [686]

Answer 1

For your usecase, rather than dealing with all those regexes, just use the Parse::Syslog module: it should be more robust and flexible in case you needed to extend your script.

use strict;
use warnings;
use Parse::Syslog;
my $syslogfile = "syslog.txt";
my $parser = Parse::Syslog->new( $syslogfile , allow_future => 1);
while(my $sl = $parser->next) {
 print "**$sl->{program}** $sl->{host} ".localtime($sl->{timestamp})." $sl->{text} [".$sl->{pid}."]\n"; }

Answer 2

SOmething like this will do. Notice that we can simplify it a lot, since the date at the beginning will always be 15 characters.

$b = "Dec 27 21:49:41 osboxes NetworkManager[686]: <info>    nameserver '192.168.221.2'";
$b =~ m/(.{15})\s+([a-z]*)\sNetworkManager(\[\d+\]):\s+(.*)/ig;
# **NetworkManager** osboxes Dec 27 21:49:41 <info>    nameserver '192.168.221.2'. [686]
print( "**NetworkManager** $2 $1 $4 $3\n" );
# prints:
# **NetworkManager** osboxes Dec 27 21:49:41 <info>    nameserver '192.168.221.2' [686]