Prolog Scripts

Appeared in Volume 10/1, February 1997

vannoord@let.rug.nl
Gertjan van Noord
23rd August 1996

A while ago someone presented a tool called 'prolog_shell' which could be used to turn a Prolog source file into a script. Such a script could be called from the command line, or become a script in a Web application for example.

There is an easier solution, which:

• does not require a specially constructed saved state;

• is more robust (prolog_shell requires exactly 2 lines of shell code followed by Prolog code);

• is more general (you can have several incarnations of Prolog in one script).

Here is an example:

#!/bin/sh
echo "<H2> Title </H2>
eval '/sysadm/web/htbin/cgiparse -form'
echo "Arguments: $FORM_a1<P>"
cat << EOF | /usr/local/bin/sicstus -f -a $FORM_a1

reconsult(user).

% Start of Prolog source file; this includes a definition for
% the predicate main/1. Its single argument is a list of input
% arguments.
...
...
...
% Change this for SICStus 3 (prolog_flag(argv,...)
:- unix(argv(Args)), main(Args).

EOF
# The EOF marks the end of the input to the SICStus command.
# You can continue your shell script here...