There is no provision in any of the standard Pascals for accessing command line data. The Borland clones provide an analog of the C/Unix world in Paramstr and Paramct.
In PascalP I handled this with a system file, called cmdline, much like input and output. It was defined at the encompassing level 0 as a read-only text file, and held a single line. To access it one could use:
reset(cmdline); cmdline^ get(cmdline); eoln(cmdline) eof(cmdline) read(cmdline, ch); read(cmdline, intvalue); (* etc *)
i.e. absolutely no extensions to the standard system. Note that it could be reset multiple times, to restart reading from the beginning. Since it is a one line file after readln(cmdline) eof(cmdline) will be true. If cmdline is empty eof(cmdline) will be true immediately after reset(cmdline).
Naturally the contents of that line depend on whatever shell launched the program.
How are the chances of adding this to gpc. The line itself must already be there for the runtime to prepare paramstr and paramct.
An advantage of this is that other systems can be source compatible. All the users need do is prepare a one line file, call it cmdline, and run the Pascal program. At the same time gpc users can still access an exterior file call cmdline, by simply defining it themselves. The 'extension' will only kick in when no "VAR cmdline : text" is in user scope.