使用perl脚本的唯一的已连接Linux用户

Question

I need to know, at any given time, how many unique users are connected to a redhat server. The following commands accomplish this easily:

who | awk '{ print $1 }' | sort -ud | wc -l

However, I need this functionality within a perl script, so that a network monitoring utility can run it at scheduled times, and track the number of unique connections over time.

While I would like to learn scripting with perl, I have no idea how long it would take to learn to script this myself, and I don't have enough time to dedicate to learning perl at the moment. Any assistance in creating a perl script with the above functionality would be greatly appreciated.

Answer 1

To easily wrap this into a perl script, do this:

#!/usr/bin/perl

$result = `who | awk '{ print \$1 }' | sort -ud | wc -l`;
print $result;

Be sure to escape $1, or else it will be interpolated by Perl.

What you do with $result after that depends on what exactly you're trying to do. You could average it over time, store every result in a file or database...it really depends on what you want to do with the result once you have it. If you'd care to provide more details I can offer some advice.

Answer 2

Assuming that you want a Perl subroutine that will return the number of users, you could do this:

 sub uniqueUsers {
    my %users;
    foreach my $line (split("\n", `who`)) {
        $users{(split(" ", $line))[0]}++;
    };
    return scalar(keys(%users));
 }

If you want a complete standalone Perl script that will just print out the total number of unique users and exit, add

#!/usr/bin/perl

as a line at the beginning, and

print uniqueUsers() . "\n";

as a final line and you're done. Oh, and make the file executable if you want to run it standalone :-)

Answer 3

To get the count:

my $usercount = `who | awk '{print $1}' | sort | uniq | wc -l`;

To get the actual usernames into an array:

my @users = `who | awk '{print \$1}' | sort | uniq`;

It's worth mentioning that learning perl basics is fairly quick (and for me, fun). I recommend picking up a copy of Learning Perl from O'Reilly Media. It's available in both paperback and in ebook format, and it is the best text book i've ever read for learning anything. Grab that one, and it won't take you long to get the basics down, despite being short on time.