topic Re: DEC C++ question in Operating System - OpenVMS

DEC C++ question

FOX MULDER_2 — Mon, 12 Nov 2007 10:37:05 GMT

Hi,

Is it possible to call DCL commands or a .com file,from DEC C/C++.

I donot have much programming skills on C/C++ except the basic ones.

Pls also suggest how to compile.

Thanks

Re: DEC C++ question

Duncan Morris — Mon, 12 Nov 2007 11:09:04 GMT

Hi Fox,

have a look at the library routines LIB$DO_COMMAND and LIB$SPAWN to see if they are suitable for what you want.

http://h71000.www7.hp.com/doc/82final/5932/5932pro_014.html#do_command

The link below will take you to the User Guide for C. It sounds as though you need to go through a few of the overview chapters to familiarise yourself with compiling C programs,

http://h71000.www7.hp.com/commercial/c/docs/5492profile_contents.html#toc_chapter_1

Regards,

Duncan

Re: DEC C++ question

Steven Schweda — Mon, 12 Nov 2007 13:29:32 GMT

HELP CRTL SYSTEM

Re: DEC C++ question

Hein van den Heuvel — Mon, 12 Nov 2007 13:34:35 GMT

[Hi Duncan]

Fox,

Many (but not all) DCL commands are available as functions and thus are more efficiently done directly from a program than from DCL... as far as the execution is concerned.

Granted, For many if us writing the code is actually more efficiently done in DCL.

If this is about a once and hour/once a day task, then by certainly just SPAWN a command(file. Just use the C build in 'system' call (or fork where appropriate).

But if you need to do something every minute or faster, or while holding a critical lock, then you may want to use a calleable interface.

Like LIB$GETJPI or CONV$CONVERT or LIB$RENAME or SYS$OPEN + XAB's to get RMS details, SYS$SNDJBC and so on.

So to help you better, you may want to provide details on what such command file is likely have to do.

Hope this helps some,
Hein van den Heuvel (at gmail dot com)
HvdH Performance Consulting

Re: DEC C++ question

Guy Peleg — Tue, 13 Nov 2007 02:29:33 GMT

Here is a simple example:

$ ty fox.c
#include

void main()
{
system ("show time");
}
$ cc fox
$ link fox
$ r fox
13-NOV-2007 00:28:08
$

Note there is a performance cost associated
with frequent system()calls.

Guy Peleg
BRUDEN-OSSG
http://www.brudenossg.com

Re: DEC C++ question

FOX MULDER_2 — Fri, 23 Nov 2007 08:06:22 GMT

Sorry for replying lately...
Thanks to all for providing the info.

Is there any C++ functions to call a DCL .com
file and execute accordingly...

An example would be very helpful.

Cheers

Re: DEC C++ question

Steven Schweda — Fri, 23 Nov 2007 08:46:36 GMT

> An example would be very helpful.

Apparently not. Try the example you already
got. If that works, try changing:
system ("show time");
to something like:
system ("@ DCL.com");