dcl / lexical functions / python

[John Tannahill]

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

[Steven Schweda]

'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?)

[John Tannahill]

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

[Steven Schweda]

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

Did you try this instead?

[Hein van den Heuvel]

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.

[John Tannahill]

Steven,

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

Thanks,
John

[John Tannahill]

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

[John Tannahill]

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

Thanks,
John

[Jean-François Piéronne]

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