command_line/1

Module: builtins

command_line/1 — provides access to the prolog system start-up command line

FORMS

command_line(SWITCHES)

DESCRIPTION

When ALS Prolog is started from an operating system shell, the command line can be divided into system-specific and application-specific portions by use of the -p or -P (for Prolog) switch. All command line parameters to the left of the -p switch are treated as ALS Prolog system switches, while those to the right of the -p switch are treated as application switches.

To make the latter available to Prolog applications, when ALS Prolog is initialized a list, SWITCHES, of atoms and UIAs representing the items to the right of the -p switch is created, and

command_line(SWITCHES)

is asserted in module builtins. This assertion is always made, even when -p is not used, in which case the argument of command_line/1 is the empty list.

The -P switch will force the name of the invoking program to be the argument(usually alspro) .. the switch is useful for developing applications which will eventually be packaged (via save_image/2). Packaged applications will place the entire command line into command_line/1. In particular, the first element in the list obtained from command_line/1 in a packaged application will be the name of the application.

EXAMPLES

$ alspro -p -k fast -s initstate foo

ALS-Prolog Version 2.01

? - command_line(SW) .

SW = [ ‘ -k ‘, fast, ‘ -s ‘, initstate, foo ]

yes.

$ alspro -P -k fast -s initstate foo

ALS-Prolog Version 2.01

? - command_line(SW) .

SW = [alspro, ‘ -k ‘, fast, ‘ -s ‘, initstate, foo ]

yes.