#!/usr/bin/perl -w
use strict;
# test on a string with just hours
my $uptime = '  9:12pm  up  2:13,  5 users,  load average: 0.84, 0.62,
+ 1.03';

if( $uptime =~ /up\s+((\d+) days,\s+)?(\S+),/ ) {
    my ($dayup,$timeup) = ( $2,$3); # $1 is the first enclosing parens
+ which we don't want
    print "timeup is ", defined $dayup ? " $dayup days and " : '', "$t
+imeup hours\n";
}
# test again on a string with days
$uptime = "6:37PM up 4 days, 2:05, 2 users, load averages: 1.99, 1.65,
+ 1.47";

if( $uptime =~ /up\s+((\d+) days,\s+)?(\S+),/ ) {
    my ($dayup,$timeup) = ( $2,$3); # $1 is the first enclosing parens
+ which we don't want
    print "timeup is ", defined $dayup ? " $dayup days and " : '', "$t
+imeup hours\n";
}
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my $uptime = '  9:12pm  up  2:13,  5 users,  load average: 0.84, 0.62,
+ 1.03';
my ($keep) = ( $uptime =~ /up\s+(.+),\s+\d+\s+users/);
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Thanks perl monks, you guys are so helpful, thanks does anyone have any helpful hints to help me with this?

For example:

use Date::Calc qw/ Normalize_DHMS /;
use IO::File;

#   get_uptime function - returns uptime from /proc/uptime
#   as 4-member array representing current system uptime in
#   days, hours, minutes and seconds

sub get_uptime {
    my $uptime;
    my $fh = IO::File->new('/proc/uptime', 'r');
    $uptime = (split /\s+/, <$fh>)[0] if defined $fh;
    return Normalize_DHMS(0, 0, 0, $uptime) if defined $uptime;
}
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my ($uptime) = /(\d+ days?, \d+:\d+)/;
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(This assumes that your original string is in the special variable $_ ).

sorry I forget to mention, this could be less than a day!

If you need to do anything other than display the results once you've isolated the uptime, you'll probably want a more useful value, such as seconds of uptime. Here's a script that will take an uptime statement and tell you the uptime in seconds. As with Stajich's solution, this may only work on uptimes of less than one year.

#! /usr/bin/perl

use strict ;
use warnings ;

use Parse::RecDescent ;

my $rules = q{
startrule:        current_time 'up' uptime remainder eol
                    { $return = $item[3] ; }
current_time:     /\d+:\d+[AP]M/
uptime:           days(?) time
                    { $return = (@{$item[1]})[0] + $item[2] ; }
days:             number_days 'days,'
                    { $return = $item[1] * 86_400 ; }
number_days:      /\d+/
time:             hours ':' minutes
                    { $return = $item[1] + $item[3] ; }
hours:            /\d+/
                    { $return = $item[1] * 3_600 ; }
minutes:          /\d+/
                    { $return = $item[1] * 60 ; }
remainder:        /.+/
eol:              /^\Z/
} ;

my $parser = new Parse::RecDescent( $rules ) ;

my @tests = (
  '11:22PM  up  4:30, 2 users, load averages: 0.25, 0.42, 0.40',
  '6:37PM up 4 days, 2:05, 2 users, load averages: 1.99, 1.65, 1.47'
) ;

foreach my $test ( @tests ) {
     print $test . ': ' .
           $parser->startrule( $test ) . "\n";
}
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