Cool script to list processes with open ports

[Dave Smith]

I stumbled across this little script while googling the fuser program,
which is worth a look if you're not familiar with it. fuser tells you
which PIDs have certain files or network ports open.

This script will list which processes are listening on which TCP/UDP ports:

<snip>
#!/bin/sh
#thanks to ideas of David A.Bandel and Myles Green
#note : fuser requires root priviledge to collect information
netstat -ln |
#keep line that starts with tcp or udp, and keep only protocol and port
sed -e '/^..[^p]/d' -e 's/0.0.0.0:\*.*//1' -e 's/ .*:/ /1' |
while read line
do
   # line is of format "tcp port-number" or "udp port-number"
   i=`fuser -n $line`
   # i is of format "port-number/protocol: PID1 PID2 ..."
   #save the part port/protocol for later use
   port=`echo $i | sed -e 's/:.*/:/g'`
   #get the array of PIDs for a given port/protocol
   j=`echo $i | sed -e 's/^.*://g'`
   for m in $j # loop for all PIDs
   do
      #display program that has predefined PID
      k=`ps -p $m -o comm -h`
      echo "$port $k"
   done
done
</snip>

Run it as root for maximum benefit. If you're not root, you'll only see
your own processes.

Enjoy!

--Dave