Sys::Statistics::Linux::NetStats - Collect linux net statistics.

    use Sys::Statistics::Linux::NetStats;

    my $lxs = Sys::Statistics::Linux::NetStats->new;
    $lxs->init;
    sleep 1;
    my $stat = $lxs->get;

    my $lxs = Sys::Statistics::Linux::NetStats->new(initfile => $file);
    $lxs->init;
    my $stat = $lxs->get;

    rxbyt    -  Number of bytes received per second.
    rxpcks   -  Number of packets received per second.
    rxerrs   -  Number of errors that happend while received packets per second.
    rxdrop   -  Number of packets that were dropped per second.
    rxfifo   -  Number of FIFO overruns that happend on received packets per second.
    rxframe  -  Number of carrier errors that happend on received packets per second.
    rxcompr  -  Number of compressed packets received per second.
    rxmulti  -  Number of multicast packets received per second.
    txbyt    -  Number of bytes transmitted per second.
    txpcks   -  Number of packets transmitted per second.
    txerrs   -  Number of errors that happend while transmitting packets per second.
    txdrop   -  Number of packets that were dropped per second.
    txfifo   -  Number of FIFO overruns that happend on transmitted packets per second.
    txcolls  -  Number of collisions that were detected per second.
    txcarr   -  Number of carrier errors that happend on transmitted packets per second.
    txcompr  -  Number of compressed packets transmitted per second.
    ttpcks   -  Number of total packets (received + transmitted) per second.
    ttbyt    -  Number of total bytes (received + transmitted) per second.

    my $lxs = Sys::Statistics::Linux::NetStats->new;

    my $lxs = Sys::Statistics::Linux::NetStats->new(initfile => '/tmp/netstats.yml');

     Sys::Statistics::Linux::NetStats->new(
        files => {
            # This is the default
            path   => '/proc',
            netdev => 'net/dev',
        }
    );

    $lxs->init;

    my $stat = $lxs->get;

package Sys::Statistics::Linux::NetStats;

use strict;
use warnings;
use Carp qw(croak);
use Time::HiRes;

our $VERSION = '0.20';

sub new {
    my $class = shift;
    my $opts  = ref($_[0]) ? shift : {@_};

    my %self = (
        files => {
            path   => '/proc',
            netdev => 'net/dev',
        }
    );

    if (defined $opts->{initfile}) {
        require YAML::Syck;
        $self{initfile} = $opts->{initfile};
    }

    foreach my $file (keys %{ $opts->{files} }) {
        $self{files}{$file} = $opts->{files}->{$file};
    }

    return bless \%self, $class;
}

sub init {
    my $self = shift;

    if ($self->{initfile} && -r $self->{initfile}) {
        $self->{init} = YAML::Syck::LoadFile($self->{initfile});
        $self->{time} = delete $self->{init}->{time};
    } else {
        $self->{time} = Time::HiRes::gettimeofday();
        $self->{init} = $self->_load;
    }
}

sub get {
    my $self  = shift;
    my $class = ref $self;

    if (!exists $self->{init}) {
        croak "$class: there are no initial statistics defined";
    }

    $self->{stats} = $self->_load;
    $self->_deltas;

    if ($self->{initfile}) {
        $self->{init}->{time} = $self->{time};
        YAML::Syck::DumpFile($self->{initfile}, $self->{init});
    }

    return $self->{stats};
}

sub raw {
    my $self = shift;
    my $stat = $self->_load;

    return $stat;
}

sub get_raw {
    my $self = shift;
    my %raw  = %{$self->{init}};
    delete $raw{time};
    return \%raw;
}

#
# private stuff
#

sub _load {
    my $self  = shift;
    my $class = ref $self;
    my $file  = $self->{files};
    my %stats = ();

    my $filename = $file->{path} ? "$file->{path}/$file->{netdev}" : $file->{netdev};
    open my $fh, '<', $filename or croak "$class: unable to open $filename ($!)";

    while (my $line = <$fh>) {
        next unless $line =~ /^\s*(\w+):\s*(.*)/;
        @{$stats{$1}}{qw(
            rxbyt rxpcks rxerrs rxdrop rxfifo rxframe rxcompr rxmulti
            txbyt txpcks txerrs txdrop txfifo txcolls txcarr txcompr
        )} = split /\s+/, $2;
        $stats{$1}{ttbyt} = $stats{$1}{rxbyt} + $stats{$1}{txbyt};
        $stats{$1}{ttpcks} = $stats{$1}{rxpcks} + $stats{$1}{txpcks};
    }

    close($fh);
    return \%stats;
}

sub _deltas {
    my $self  = shift;
    my $class = ref $self;
    my $istat = $self->{init};
    my $lstat = $self->{stats};
    my $time  = Time::HiRes::gettimeofday();
    my $delta = sprintf('%.2f', $time - $self->{time});
    $self->{time} = $time;

    foreach my $dev (keys %{$lstat}) {
        if (!exists $istat->{$dev}) {
            delete $lstat->{$dev};
            next;
        }

        my $idev = $istat->{$dev};
        my $ldev = $lstat->{$dev};

        while (my ($k, $v) = each %{$ldev}) {
            if (!defined $idev->{$k}) {
                croak "$class: not defined key found '$k'";
            }

            if ($v !~ /^\d+\z/ || $ldev->{$k} !~ /^\d+\z/) {
                croak "$class: invalid value for key '$k'";
            }

            if ($ldev->{$k} == $idev->{$k} || $idev->{$k} > $ldev->{$k}) {
                $ldev->{$k} = sprintf('%.2f', 0);
            } elsif ($delta > 0) {
                $ldev->{$k} = sprintf('%.2f', ($ldev->{$k} - $idev->{$k}) / $delta);
            } else {
                $ldev->{$k} = sprintf('%.2f', $ldev->{$k} - $idev->{$k});
            }

            $idev->{$k} = $v;
        }
    }
}

1;