Regex question

[kbshaq]

I'm trying to match hostnames from a DNS zone file. Here's a sample line:

host.domain.com. A 192.168.0.1


How do I match just "host.domain.com"? That is, what regex would I use?

Thanks,
-KB

[miller]

You need to more explicitly state what you're trying to do. Are you trying to simply see if this "specific" hostname is within a line. Are you trying to extract the hostnames? And they are always the first item in the record? There are many different types of goals that would require a different regular expression, but since you didn't specify, I'll simply assume the easiest.

if ($line =~ m{\b\Qhost.domain.com\E\b}) {
    print "specific host found";
} else {
    print "not found";
}
 

All that does is search for the literal string "host.domain.com" with word boundaries surrounding it. If you need help with anything more specific, you'll have to specify.

[kbshaq]

You need to more explicitly state what you're trying to do. Are you trying to simply see if this "specific" hostname is within a line. Are you trying to extract the hostnames? And they are always the first item in the record? There are many different types of goals that would require a different regular expression, but since you didn't specify, I'll simply assume the easiest.

if ($line =~ m{\b\Qhost.domain.com\E\b}) {
    print "specific host found";
} else {
    print "not found";
}
 

All that does is search for the literal string "host.domain.com" with word boundaries surrounding it. If you need help with anything more specific, you'll have to specify.

Sorry, miller.

Yes, I will extract only the hostnames and they will be the 1st item in the record.

Okay, I saw that you used the word boundary -- I didn't think to use that. :)

Thanks!!

[miller]

If all you're trying to do is extract the first element from the line, then I suggest simplifying your logic:

if ($line =~ m{^(\S+)}) {
    push @hostnames, $1;
}
 

The above simply pulls all characters until a space is reached. It is the simpliest logic that you could use, and will therefore catch all your hostnames.