The Nemesis Project is designed to be a commandline-based, portable human IP stack for UNIX/Linux (and now Windows!). The suite is broken down by protocol, and should allow for useful scripting of injected packet streams from simple shell scripts. If you enjoy Nemesis, you might also want to look at Hping as they complement each other well.
For downloads and more information,
visit the Nemesis homepage.
The libnet headers can be manipulated to get this to still function with the correct library version but its insanely difficult to track and resolve. I would consider this project dead or good practice for the coding community to get it functional again.