Using command line arguments (see section
2.4), SWI-Prolog can be forced to load files and execute queries for
initialisation purposes or non-interactive operation. The most commonly
used options are
-f file or -s file
to make Prolog load a file,
-g goal to define initialisation goals and
-t goal to define the top-level goal.
The following is a typical example for starting an application directly
from the command line.
machine% swipl -s load.pl -g go -t halt
It tells SWI-Prolog to load load.pl, start the
application using the entry point go/0 and ---instead of
entering the interactive top level--- exit after completing go/0 .
The command line may have multiple -g goal
occurrences. The goals are executed in order. Possible choice points of
individual goals are pruned. If a goal fails execution stops
with exit status
1. If a goal raises an exception, the exception
is printed and the process stops with exit code 2.
The -q may be used to suppress all informational
messages as well as the error message that is normally printed if an
initialisation goal fails.
In MS-Windows, the same can be achieved using a short-cut with
appropriately defined command line arguments. A typically seen
alternative is to write a file run.pl with content as
illustrated below. Double-clicking run.pl will start the
application.
:- [load]. % load program
:- go. % run it
:- halt. % and exit
Section 2.11.1.1
discusses further scripting options, and
chapter 14 discusses the
generation of runtime executables. Runtime executables are a means to
deliver executables that do not require the Prolog system.
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