-- is the argument that should stop the processing of further arguments for Jawk, and pass the rest as ARGV to the AWK script

[bertysentry]

Currently, the - (simple dash) argument is a special argument to signals to Jawk that the rest of the arguments in the command line should not be parsed, but be considered as inputs to the AWK script (or variables, etc.).

But POSIX requires -- (double dash) to be this special argument. Simple dash means stdin as an input.

Also, gawk doesn't require --: the first "unknown" option passed as an argument is considered the end of the official gawk arguments, and the rest is considered as input files, variable assignments, and passed in ARGV.

See gawk's manual page.