Magic Variables in Bash

• $0 - $99 x-th argument provided to the script/function. $0 is always the script name even when accessed from within a function. $1+ will work in functions.

• $? Exit code of the last process.

• $_ Last argument.

• $! PID of last process.

• $@ All arguments.

Note: Always quote variables to avoid word-splitting (except when using [[ for tests). Run shellcheck to make sure.