Linux Perl Lite version netstat

Article Title: Linux Perl Lite version netstat. Linux is a technology channel of the IT lab in China. Includes basic categories such as desktop applications, Linux system management, kernel research, embedded systems, and open source.

Writing intention:

The built-in netstat of Linux system often finds that the CPU usage is high when capturing information, especially when some monitoring systems are used, if netstat is used, the monitoring system itself may cause a high system load. Therefore, you can use perl to write down the log. The time test is faster and more resource-saving than the built-in netstat. 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 %-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 ("%-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 %-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 %-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;
}