topic dcl / lexical functions / python in Operating System - OpenVMS

dcl / lexical functions / python

John Tannahill — Wed, 24 Oct 2007 13:06:29 GMT

If I interactively execute:
sh log sys$output
I get:
"SYS$OUTPUT" = "_RIPPLE$FTA40:" (LNM$PROCESS_TABLE)

Likewise if I execute:
output = f$trnlmn("sys$output")
write sys$output "''output'"
I get:
_RIPPLE$FTA40:

I would like to create a Python interface to f$trnlmn.

If I do:
pipe = os.popen('f$trnlmn("sys$output")')
output = pipe.read()
err = pipe.close
sys.stdout.write(output)

I get (as expected):
%DCL-W-IVERB, unrecognized command verb - check validity and spelling
\F$TRNLMN\

If I do:
pipe = os.popen('output = f$trnlmn("sys$output)')

It runs, but I don't know how to get the contents of 'output' back into the Python process?

Suggestions?

Thanks,
John

Re: dcl / lexical functions / python

Steven Schweda — Wed, 24 Oct 2007 13:19:33 GMT

'write sys$output f$trnlnm("sys$output")' in
the os.popen()?

> %DCL-W-IVERB [...]

F$TRNLNM is not a command. WRITE is.

Note that it _is_ F$TRNLNM, not F$TRNLMN.
(TRaNslate Logical MiNnesota?)

Re: dcl / lexical functions / python

John Tannahill — Wed, 24 Oct 2007 13:52:01 GMT

Steven,

That's why the error was "expected".

Sorry about the typo, everything else still holds.

Still need to be able to get the contents of 'output' back into the Python process.

John

Re: dcl / lexical functions / python

Steven Schweda — Wed, 24 Oct 2007 13:56:18 GMT

> 'write sys$output f$trnlnm("sys$output")' in
> the os.popen()?

Did you try this instead?

Re: dcl / lexical functions / python

Hein van den Heuvel — Wed, 24 Oct 2007 13:58:44 GMT

John,

Seems to me you are entirely on the wrong track here!

I thought you wanted to get away from DCL?
[ http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=1159356 ]

The F$stuff is strictly and only DCL and requires a process running DCL for you. Yuck!

The F$Stuff is 99% directly built on real system services like SYS$TRNLNM.

Just judging by the examples in the Jean-Francois' OpenVMS article those system services as nicely, directly, available in Python... so cut out the middle man (DCL).
See: http://h71000.www7.hp.com/openvms/journal/v6/python-openvms-jfp.html

But what is worse... if you open a process, you'll talk to it via a pipe and the sys$output logical name for that process will not be same as the one you are trying to look up. It will point to a pipe (mailbox), not a terminal.

You may want to check out 'get_logical' in the Python Reference manual:

http://vmspython.dyndns.org/docs/python_vms/installation_manual.html

dig dig dig dig

Cheers,
Hein.

Re: dcl / lexical functions / python

John Tannahill — Wed, 24 Oct 2007 14:02:25 GMT

Steven,

Your suggestion worked. Pretty straightforward, just didn't think of it.

Thanks,
John

Re: dcl / lexical functions / python

John Tannahill — Wed, 24 Oct 2007 14:05:30 GMT

Hein,

Never fear, in the end the DCL will be gone, but it will be a while. Just taking baby steps right now. Trying to understand things, etc. I have no prior knowledge of the DCL code.

Thanks for your suggestions,
John

Re: dcl / lexical functions / python

John Tannahill — Wed, 24 Oct 2007 14:11:06 GMT

pipe = os.popen('write sys$output f$trnlnm("sys$output")') worked.

Thanks,
John

Re: dcl / lexical functions / python

Jean-François Piéronne — Fri, 26 Oct 2007 02:35:43 GMT

John,

import vms.rtl.lib
vms.rtl.lib.get_logical('SYS$OUTPUT')

or

import os
os.getenv('SYS$OUTPUT')

will do the job,

lib$get_logical puts something in the first 4 characters and then puts the logical translation, it's not a Python bug...

getenv has not the problem.

JF