What do backticked options mean?

Question

I noticed this command:

gcc -Wall `libnet-config --defines` libnet-example-x.c -o libnet-example-x `libnet-config --libs`

What is the meaning of libnet-config --defines and libnet-config --libs?

Answer 1

It is executing a program that generates the necessary gcc arguments to compile an application that uses libnet.

Execute this at the command line and you will see what is going on:

 libnet-config --defines

Answer 2

libnet-config is an executable that will return a list of -D... options for gcc when called with the argument --defines and a list of -l... with the other argument.