topic Re: symbols in Operating System - OpenVMS

symbols

John Tannahill — Wed, 24 Sep 2008 23:53:38 GMT

I am working in an openvms alpha environment, but have relatively little openvms experience. I have an issue that I describe below. There must be an easy answer?

$ sh sym python
PYTHON == "$ python_root:[vms.bin]python"

$ sh log python_root
"PYTHON_ROOT" = "$2$DKA0:[3RD_PARTY.PYTHON.PYTHON250.]" (LNM$SYSTEM_TABLE)

The python symbol works as it should:
* If I type “python”, I go into an interactive python session.
* If I type “python xdoit.py”, xdoit.py is run.

But if I try to execute the symbol contents directly, i.e.:
$ $ python_root:[vms.bin]python
Or:
$ $ python_root:[vms.bin]python xdoit.py
These do not work?
And for both, I get:
%DCL-W-NOLBLS, label ignored - use only within command procedures
\PYTHON_ROOT:\
%DCL-W-NOCOMD, no command on line - reenter with alphabetic first character

If I get rid of one of the starting dollar signs, I still get the same error.

What is going on here and what do I need to do to get the latter cases to work?

Thanks,
John

Re: symbols

Thomas Ritter — Thu, 25 Sep 2008 00:11:49 GMT

John, to run PYTHON

either

$ PYTHON

or

$ r python_root:[vms.bin]python

Re: symbols

John Tannahill — Thu, 25 Sep 2008 00:31:55 GMT

Thanks Thomas, that works for the simple case, but what about:

$ r python_root:[vms.bin]python xdoit.py

The run command does not seem to like me passing the xdoit.py argument? Could not find any examples of run using arguments in the online documentation.

John

Re: symbols

Thomas Ritter — Thu, 25 Sep 2008 00:34:33 GMT

John,

$ PYTHON xdoit.py

The concept is called foreign commands.

Re: symbols

John Tannahill — Thu, 25 Sep 2008 00:48:59 GMT

Got enough info to point me in the right direction for what I am trying to do.

Re: symbols

John Gillings — Thu, 25 Sep 2008 01:52:20 GMT

John,

>$ r python_root:[vms.bin]python xdoit.py
>

>The run command does not seem to like me
>passing the xdoit.py argument?

That's correct. The DCL RUN command doesn't understand parameters. There are several ways of passing parameters to images, here are a few. In each case is the full file specification of the target image.

1) Define a foreign command symbol

$ foreign_command="$"
$ foreign_command parameter parameter...

2) use the DCL$PATH logical name

$ DEFINE DCL$PATH dir1,dir2,dir3,...
$ image-name parameter parameter

(in this case image-name is just the name, not the full file specification)

3) use the (undocumented) MCR command

$ MCR parameter parameter...

4) define a DCL command using the CLD utility and call CLI$ routines to determine values of parameters and qualifiers.

Re: symbols

Steven Schweda — Thu, 25 Sep 2008 02:01:33 GMT

> [...] relatively little openvms experience.

The FAQ covers many useful topics:

http://www.hoffmanlabs.com/vmsfaq/

Re: symbols

John Tannahill — Thu, 25 Sep 2008 16:21:15 GMT

John & Steven,

I have learned a valuable lesson - not to close my posts too hastily. I would like to give you guys points, but it appears that I cannot?

It turns out that for us, the optimal solution appears to be to use DCL$PATH. It is less intrusive than adding a command to the command table (& easier in general).

Thanks for your help!
John

Re: symbols

Robert Gezelter — Thu, 25 Sep 2008 16:54:52 GMT

John,

The series of columns that I did for OpenVMS.org on logical names and related topics may also be of interest.

They are cross linked, but the last one [on logical names] can be found at http://www.openvms.org/stories.php?story=03/03/03/4358185

There are also some other presentations that I have done in the past for Connect [the user group] (fka Encompass, fka DECUS). Those can be reached via my firm's presentations page at http://www.rlgsc.com/presentations.html

I hope that the above is helpful.

- Bob Gezelter, http://www.rlgsc.com

Re: symbols

Joseph Huber_1 — Fri, 26 Sep 2008 10:10:02 GMT

>> the optimal solution appears to be to use DCL$PATH.

This is true for most executables or command-files.
In the case of python as far I know it is not enough to know the main executable, but it needs some more definitions/logicals pointing to a phython root directory. Therefore it needs some kind of setup file, which then can have the command definition as well.