Path: utzoo!attcan!uunet!lll-winken!lll-tis!helios.ee.lbl.gov!pasteur!ucbvax!VENUS.YCC.YALE.EDU!LEICHTER
From: LEICHTER@VENUS.YCC.YALE.EDU ("Jerry Leichter ", LEICHTER-JERRY@CS.YALE.EDU)
Newsgroups: comp.os.vms
Subject: re: Subprocess creation problem
Message-ID: <8805260732.AA18842@ucbvax.Berkeley.EDU>
Date: 24 May 88 15:26:00 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 56


	I have been having a problem with a program creating a process
	using CREPRC.  If the output of the executable has been 
	redirected in ANY way it doesn't create the subprocess and execute
	the commands in the datafile....	

	For example,
	The program works fine when I use the following DCL commands:

	$RUN DETACH_PROG
	$TYPE SYS$LOGIN:DETACH_PROG.LOG
	[....log file is here with information...]

	HOWEVER,
	If I use the /INPUT, /OUTPUT or /DETACH qualifier the program 
	doesn't create the log file and doesn`t execute the commands in
	DETACH_PROG.DAT.  It seems ANY redirection of I/O to the program
	will cause the subprocess not to be created.
	
	For example,

	$RUN DETACH_PROG /OUTPUT=SYS$LOGIN:ANYTHING.HERE
	$TYPE SYS$LOGIN:DETACH_PROG.LOG
	
	or

	$RUN DETACH_PROG /DETACH
	$TYPE SYS$LOGIN:DETACH_PROG.LOG

	[produce no output.]

Using any of /INPUT, /OUTPUT, or /DETACH produces a detached process, one
that is not part of your job tree; so all the examples you've had problems
with end up looking pretty much the same.  They are, in fact, all running
into the same "gotcha'":  The file spec you provide for /INPUT or /OUTPUT
is passed, COMPLETELY UNINTERPRETED, to the created process.  The created
process will then try to open the file.  It must be able to do so, IN ITS
OWN CONTEXT; that is, any logicals used in the file specs must be defined in
that context.

When you create a detached process, it starts out with its own job table,
so it can't inherit the job-wide definition of SYS$LOGIN that the creating
process has.  Well, where did that definition come from?  LOGINOUT put it
there when the process logged in.  A process created with $CREPRC (or RUN/DET)
does NOT run LOGINOUT (although you can have it do so explicitly).  Hence, it
has no definition for SYS$LOGIN, so its attempt to open its output file fails.
Boom.

How could you have found this out yourself?  When a process dies, unless it
has disabled accounting (not the case here), its final exit status is written
to the accounting file.  If you had used the ACCOUNTING command to check the
accounting record for your processes, you would probably have found that the
final exit status was "failed to open output file", or some such.  Not a huge
amount of information - without knowing about the problem with logicals,
probably not enough to let you figure out what is going on - but sometimes
enough to get you started.
							-- Jerry