What is the "Zeroth Argument" in the Command-Line?
The zeroth argument is the name of the terminal command you type in the command-line, which may be the filepath of a program or a built-in shell utility that you want to execute.
For example, in cd Pictures, the zeroth argument is cd. Arguments can contain multiple words when surrounded by quotes in some shells, e.g. in "./build script.py" --test the zeroth argument would be ./build script.py.