A.27 library(main): Provide entry point for scripts
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Availability::- use_module(library(main)).(can be autoloaded)
Sourcemain
Call main/1 using the passed command-line arguments. Before calling main/1 this predicate installs a signal handler for SIGINT (Control-C) that terminates the process with status 1.

When main/0 is called interactively it simply calls main/1 with the arguments. This allows for debugging scripts as follows: 

$ swipl -l script.pl -- arg ...
?- gspy(suspect/1).		% setup debugging
?- main.			% run program