Linux系统Perl精简版netstat

    写作意图：

    Linux系统自带的netstat在很多时候抓信息会发现耗CPU很高，特别是在做一些监控系统的时候，发现如果使用了netstat，监控系统本身会造成系统负载比较高，因此试着用perl写下，time测试比自带的netstat更快更节省资源，欢迎批评，呵呵。

    #!/usr/bin/perl
    # Written by FinalBSD at 2008-11-20.

    # The netstat original written by C
    # is expensive to me, so this born.
    # As long as you retain this notice you
    # can do whatever you want with this stuff.
    # If we meet some day, and you think
    # this stuff is worth it, you can
    # buy me a beer in return.
    use strict;
    use warnings;
    use Getopt::Std;
    my $tcp     = "/proc/net/tcp";
    my $tcp6     = "/proc/net/tcp6";
    my $route    = "/proc/net/route";
    my @tcpState     = (
    "NULL",
    "ESTABLISHED" ,
    "SYN_SENT",
    "SYN_RECV",
    "FIN_WAIT1",
    "FIN_WAIT2",
    "TIME_WAIT",
    "CLOSE",
    "CLOSE_WAIT",
    "LAST_ACK",
    "LISTEN",
    "CLOSING"
    );
    my @routeType   = (
    "NULL",
    "U",        # UP
    "G",        # Gateway
    "UG"        # UP & Gateway
    );
    my %opts;
    getopts('nhatsrl', \%opts);
    if($opts{h}) {
    &usage();
    }
    if($opts{r}) {
    &route_info($route);
    exit;
    }
    &tcp_info($tcp);
    &tcp_info($tcp6);
    ###################### FUNCTION DEFINITION ###########################
    #############################
    # Get statistics Information
    ############################
    sub tcp_info($) {
    my $file = shift;
    open(FH, $file) or die("$!");
    my $format = "%-30s  %-30s %-10s\n";
    printf($format,"      Local Address","      Foreign Address","State");
    while() {
    next if /local_address/;
    my @data = split;
    my $state = $tcpState[hex($data[3])];
    # Show listening Sockets.
    if($opts{l}){
    printf($format, &hextoint($data[1]), &hextoint($data[2]), $state) if $state =~ /LIST/;
    } else {
    printf($format, &hextoint($data[1]), &hextoint($data[2]), $state);
    }
    }
    close(FH);
    }
    #############################
    # Convert hex to int
    ############################
    sub hextoint($) {
    my $tmp     = shift;
    my @data;
    my @ip;
    my $int;
    # if have ':', then it's  addr:port,else just port.
    if( $tmp =~ /:/ ) {
    if( $tmp =~ /FFFF/ ) {
    @data = split /:/, $tmp;
    # break it and do convert later.
    @ip   = $data[0] =~ /\w{2}/g;
    foreach my $index (12..15){
    $ip[$index] = hex($ip[$index]);
    }
    $int  = sprintf("%-5s %d.%d.%d.%d:%d", "tcp6",$ip[15], $ip[14], $ip[13], $ip[12], hex($data[1]));
    } else {
    @data = split /:/, $tmp;
    @ip   = $data[0] =~ /\w{2}/g;
    foreach my $index (0..3){
    $ip[$index] = hex($ip[$index]);
    }
    $int  = sprintf("%-s %d.%d.%d.%d:%d", "     ",$ip[3], $ip[2], $ip[1], $ip[0], hex($data[1]));
    }
    } else {
    @ip   = $tmp =~ /\w{2}/g;
    foreach my $index (0..3){
    $ip[$index] = hex($ip[$index]);
    }
    $int  = sprintf("%d.%d.%d.%d", hex($ip[3]), hex($ip[2]), hex($ip[1]), hex($ip[0]));
    }
    return $int;
    }
    #############################
    # Show Kernel route table
    ############################
    sub route_info($) {
    my $routefile = shift;
    open(ROUTE, $routefile) or die ("Can't open route file!\n");
    my $header = "Iface  Destination     Gateway      Flags   Genmask\n";
    printf("%s", $header);
    my $format = "%-5s %-15s %-15s %-5s %-15s\n";
    while() {
    next if /Iface/;
    my @line = split;
    my ($iface, $dest, $gw, $flags, $mask ) = ($line[0], &hextoint($line[1]), &hextoint($line[2]), hex($line[3]), &hextoint($line[7]));
    printf($format, $iface, $dest, $gw, $routeType[$flags], $mask );
    }
    close(ROUTE);
    }
    #############################
    # Show help information
    ############################
    sub usage {
    printf("%s\n\n%-30s\n%-30s\n%-30s\n%-30s\n%-30s\n%-30s\n",
    "netstat written in Perl by FinalBSD.Copyright(c) 2008.",
    "-n Show numeric ip and port address.",
    "-r Display the kernel routing table.",
    "-a Show both listening and non-listening socktes.",
    "-t Show only TCP statistics.",
    "-l Show only listening sockets.",
    "-h Show help.",
    );
    exit;
    }