SCOUG-Programming Mailing List Archives

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Date:	Tue, 26 Oct 1999 08:39:12 PDT
From:	Peter Skye <pskye@peterskye.com >
Reply-To:	scoug-programming@scoug.com
To:	scoug-programming@scoug.com
Subject:	SCOUG-Programming: REXX file lock/unlock, program instances

Content Type: text/plain

Aaron Lawrence wrote:
>
> > -- How do I lock a file,
>
> In rexx, all files are opened non-share, so
> are automatically locked (AFAIK) and no other
> program can access them

Hi Aaron,

I wrote some test programs just now (Warp 4 FixPak 10), and they allow
me to open a file in one program and, while the file remains open, open
and read the file in another program. Thus, the files aren't locked
while open. This may be specific to OS/2 and other platforms may lock
the files while open.

> > -- How can an executing REXX .cmd file
> > find out if it is already running?
>
> Some sort of nasty external flag e.g. create
> a file at startup. ... Unfortunately ... you
> can't use OS/2 semaphores which are better,

Mutexes were added in one of the FixPaks (I have them in FixPak 10 and
they seem to work fine). I was hoping there would be some one-line
solution. (The documentation is only in \OS2\BOOK\OREXX.INF under
Rexx Utilities (RexxUtil) but the mutex semaphores are in both Object
Rexx and Classic Rexx. Don't know why the Classic Rexx documentation
wasn't updated.)

> Basically Rexx is best not used for situations where
> multiprocessing matters (or any "serious" task) IMHO

I very much agree. I'm trying to move a set of old DOS programs over to
OS/2 and I'm hoping I can glue everything together with some Rexx.

Thanks. :)

- Peter

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