This is a Python script that can be used with GDB. It imports modules from Jonathan Salwan's ROPgadget tool located at https://github.com/JonathanSalwan/ROPgadget. As such, it's actually a dependency that must be install via pip install ropgadget or pip3 install ropgadget. Otherwise this script won't be very valuable at all.
pip install ropgadget or
pip3 install ropgadget
run gdb then type source ROPgadget.py
In order for ROPgadget to work a file must be loaded into gdb's current running state. For example you can type: file /bin/ls and then type ROPgadget to find all the gadgets inside the ls binary. help ROPgadget will give you any available options