Quintus Prolog Manual

G-3: Invoking Prolog

G-3-1: Prolog Command Line Argument Handling

There are three ways a Prolog system can be invoked:

        % <program> <Prolog's arguments>

        % <program> <Prolog's arguments> + <emacs' arguments>

        % <program> <Prolog's arguments> +z <user's arguments>

Where <program>, generally Prolog, but can be an executable QOF file (see section G-5-4) or a stand-alone program (see Chapter H-1).

<Prolog's arguments> consists of:

<user's arguments>

these arguments can be retrieved in a program by calling unix(argv(ArgList)).

<system arguments>

The current valid system arguments are:

+

invoke Emacs; subsequent arguments passed to Emacs;

+f

fast startup; do not load user's prolog.ini file;

+l <file>

load the specified file on startup; <file> may be a Prolog file or a QOF file, and it may be specified either as a string (eg. 'file', '~/prolog/file.pl) or as a file search path specification (eg. 'library(file)', 'home(language(file))'); note, however, that the latter needs to be quoted to escape the shell interpretation of the parentheses; giving the extension is not necessary; if both source (.pl) and QOF (.qof) files exist, the more recent of the two will be loaded;

+L <file>

like +l, but search for file in the directories given by the shell environment variable PATH; and

+p [<path-name>]

prints the Prolog file search path definitions that begin with the string <path-name> (eg. library if "+p lib" is specified); <path-name> is optional, and if not given, causes prolog to print all file search path definitions; prolog exits after producing the required output to stdout;

+P [<path-name>]

same as +p, but the absolutized versions of the file search path definitions are printed;

+tty

force the three standard streams associated with a Prolog process to act as tty streams; a tty stream is usually line buffered and handles the prompt automatically;

+z

all subsequent arguments are user's arguments.

Only one of + or +z is possible on one command line.

<emacs' arguments>

arguments to the Emacs interface. This may include file names to edit and may also include GNU Emacs arguments (see Chapter D-2).

All command line arguments beginning with a + are reserved for system arguments. If user arguments need to begin with a +, they should be given as ++ instead. The ++ is converted into a single + by the argument handling routines, and thus, to the user's code, only the single + argument is visible. An exception to this is when an argument is given following a +z option in which case no conversion is done.

Runtime systems do not interpret system arguments; they treat all arguments as user's arguments.

There can be any number of +l and +L arguments. In Release 3, invoking a saved-state, an executable QOF-file, as a Unix command causes the corresponding Prolog executable, the one from which the saved-state was created, to be invoked with the arguments "+L <saved-state>".

The user's arguments are accessible in Prolog via unix(argv(ArgList)), which returns a list of all the user's arguments. For example, if Prolog is invoked by the command (A), then the Prolog goal (B) returns (C):

        % prolog ++file1 -file2                                                                                                                                                                      (A)

        | ?- unix(argv(ArgList)).                                                                                                                                                                    (B)

        ArgList = ['+file1','-file2']                                                                                                                                                                (C)

G-3-1-1: The Initialization File

Once invoked, the default prolog looks in your home directory for a file named prolog.ini, and if it finds one, loads it. Stand-alone programs also look for and load prolog.ini. Runtime systems do not.

Typically, prolog.ini files are used to define file search paths, library directories, and term expansions.

If the +f option is specified, the initialization file prolog.ini is not loaded.

G-3-2: Exiting Prolog

To exit from the Prolog system, either type

        | ?- halt.

 

   

           without Emacs:  type '^d' (or '^C e'). You may
                                also execute the goal halt/0.
           with GNU Emacs: type '^c ^d' (or 'Escape-X
                          exit-emacs').
           with QUI:       Use Interrupt button in main window.
                           Select Exit.

   

If you would like to pause Prolog while keeping the job in the background:

   

without Emacs: type '^Z'.
with GNU Emacs: type '^X^Z'.
with QUI: iconify the main window

   

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