Perl Lite version netstat

Writing intention:
The built-in netstat in Linux system often finds that CPU consumption is high when capturing information, especially when some monitoring systems are used,
It is found that if netstat is used, the monitoring system itself will cause a high system load, so try to write it in Perl. The time test is better than the built-in
Netstat is faster and more resource-saving. Thank you for your criticism.

#! /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 = "%-30 S %-30 S %-10 s/n ";
Printf ($ format, "Local Address", "foreign address", "State ");
While (<FH> ){
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 ("%-5 S % 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 = "%-5 S %-15 S %-15 S %-5 S %-15 s/n ";
While (<Route> ){
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 %-30 s/n %-30 s/n %-30 s/n %-30 s/n %-30 s/n % -30 s/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;
}