Perl

Some one liners: socher.org

A one-line web server!

perl -MIO::All -e 'io(":8080")->fork->accept->(sub { $_[0] < io(-x $1 ? "./$1 |" : $1) if /^GET \/(.*) / })'

• First we accept a socket and fork the server. Then we overload the new socket as a code ref. This code ref takes one argument, another code ref, which is used as a callback.
• The callback is called once for every line read on the socket. The line is put into $_ and the socket itself is passed in to the callback.
• Our callback is scanning the line in $_ for an HTTP GET request. If one is found it parses the file name into $1. Then we use $1 to create an new IO::All file object... with a twist. If the file is executable("-x"), then we create a piped command as our IO::All object. This somewhat approximates CGI support.
• Whatever the resulting object is, we direct the contents back at our socket which is in $_[0].

From: commandlinefu.com

What Perl modules are installed?

As found by typing "perldoc q installed"

#!/usr/bin/perl
use File::Find;
           my @files;
           find(
             sub {
               push @files, $File::Find::name
                       if -f $File::Find::name && /\.pm$/
               },
             @INC
             );
               print join "\n", @files;

Install a Perl module using Perl

perl -MCPAN -e 'install RRD::Simple'

Send an email from perl without needing any external modules

but it only works on Unix :(

#	Simple Email Function
#	($to, $from, $subject, $message)
sub sendemail
{
    my ($to, $from, $subject, $message) = @_;
    my $sendmail = '/usr/lib/sendmail';
    open(MAIL, "|$sendmail -oi -t");
    print MAIL "From: $from\n";
    print MAIL "To: $to\n";
    print MAIL "Subject: $subject\n\n";
    print MAIL "$message\n";
    close(MAIL);
}

Using the function is straightforward. Simply pass it the data in the correct order.

sendemail ( "toemail\@mydomain.com", "fromemail\@mydomain.com", "Simple email.", "This is a test of the email function." );

Difference in hours between two dates

use Time::localtime;
use DateTime::Format::Strptime qw();

        my $parser = DateTime::Format::Strptime->new (
            pattern  => '%d-%b-%y %H:%M:%S',
            locale   => 'en',   # 'Mon', 'Jul' are English
            on_error => 'croak'
        );
        my $timethen = $parser->parse_datetime( $started );
        my $timenow  = DateTime->now( time_zone => 'local' )->set_time_zone('floating');
        my $timediff = $timenow->subtract_datetime($timethen);

print ('<!-- HOURS: ',$timediff->hours(),' -->',"\n");

or, without using any external modules...

        my ($host,$sid,$dbid,$timethen,$recid,$stamp,$started,$duration,$size,$status,$type) = split (/\|/);

        # ----------------------------
        # work out how old the file is
        # ----------------------------
        my $timenow    = time();
        my $difference = $timenow - $timethen;  # in seconds
        my $hours      = $difference/60/60;
        $difference    = $difference - ($hours*60*60);
        my $mins       = $difference/60;
        my $secs       = $difference - ($mins*60);

Slurp an external file into a variable

The idea is to read an SQL file into a variable to prepare and execute it

#!/usr/bin/perl -w
use strict;
my $stmt;
my $quoted_stmt;
$quoted_stmt = 7;
open (FH,"<","test.sql") or die $!;
local $/='';
$stmt = <FH>;
close FH;
$quoted_stmt = eval('q('.$stmt.')');
print $quoted_stmt."\n";