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main.pl -- Provide entry point for scripts
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This library is intended for supporting PrologScript on Unix using the #! magic sequence for scripts using commandline options. The entry point main/0 calls the user-supplied predicate main/1 passing a list of commandline options. Below is a simle echo implementation in Prolog.

#!/usr/bin/env swipl

:- initialization(main, main).

main(Argv) :-

echo([]) :- nl.
echo([Last]) :- !,
    write(Last), nl.
echo([H|T]) :-
    write(H), write(' '),
See also
- library(optparse) for comprehensive option parsing.
- library(prolog_stack) to force backtraces in case of an uncaught exception.
- XPCE users should have a look at library(pce_main), which starts the GUI and processes events until all windows have gone.
Source main
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.
Source interrupt(+Signal)[private]
We received an interrupt. This handler is installed using on_signal/3.
Source argv_options(+Argv, -RestArgv, -Options) is det
Generic transformation of long commandline arguments to options. Each --Name=Value is mapped to Name(Value). Each plain name is mapped to Name(true), unless Name starts with no-, in which case the option is mapped to Name(false). Numeric option values are mapped to Prolog numbers.
See also
- library(optparse) provides a more involved option library, providing both short and long options, help and error handling. This predicate is more for quick-and-dirty scripts.
Source cli_parse_debug_options(+OptionsIn, -Options) is det
Parse certain commandline options for debugging and development purposes. Options processed are below. Note that the option argument is an atom such that these options may be activated as e.g., --debug='http(_)'.
Call debug(Topic). See debug/1 and debug/3.
spy Predicate
Place a spy-point on Predicate.
As spy using the graphical debugger. See tspy/1.
Start the Prolog toplevel after main/1 completes.
Source cli_enable_development_system
Re-enable the development environment. Currently re-enables xpce if this was loaded, but not initialised and causes the interactive toplevel to be re-enabled.

This predicate may be called from main/1 to enter the Prolog toplevel rather than terminating the application after main/1 completes.