help me
 

how to write code in network simulator using linux commands? how to execute it?

Welcome to LQ, jhananie,

This forum is full of helpful volunteers that would be willing to answer your question. However, it is very inaccurately and vaguely worded. The title "help me" reveals nothing about your problem and will cause lots of people to ignore this thread. This also tells us you have not read the LQ FAQ.
A better title for this thread would be "linux commands to write and execute code in Network-Simulator-You-Are-Using". Users of that network simulator will see it and help you.
This brings me to another issue: which network simulator are you using? ns2/ns3? OPNET? NetSim? GNS?

I'm assuming you mean "what should I type in my console/terminal emulator?" when asking for a command. I'm also assuming you know how to use the simulator.
In that case, install the simulator and type
to view the manual. If you can't find it there or if the simulator doesn't have a man page, look on their website and as a last resort, go to the distro's package database. Find the package and look for a "file list". Look for filenames that start with "/usr/bin/", "/usr/local/bin/" that do not contain any more slashes. Type the filename in your console/terminal. ("/usr/bin/ns2" would mean you have to type "ns2")
I that doesn't work try adding a space and "-h" or "--help" to the command.

Good luck.

PS. below you will see 2 links. Click them.