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| Title: | -={ H A C K E R S }=- |
| Notice: | Write locked - see NOTED::HACKERS |
| Moderator: | DIEHRD::MORRIS |
|
| Created: | Thu Feb 20 1986 |
| Last Modified: | Mon Aug 03 1992 |
| Last Successful Update: | Fri Jun 06 1997 |
| Number of topics: | 680 |
| Total number of notes: | 5456 |
656.0. "Null devices" by EAGLE1::KIRK (Matthew Kirk) Fri Jan 08 1988 14:38
In order to avoid a tremendous amount of unnecessary processing, I
want to add code to a program to check to see if the output device
specified is a null device. Originally I thought I would do this by
checking the device specified in the NAM block returned by $OPEN (which
calls $PARSE to get the actual path of the file to be opened).
This parses any logicals that the user may have set up, but it seems
that the only way to tell that the file is actually on a null device
is the convention that null devices are called NLxx:.
The problem is that this is only a convention, and I can find nothing
in any of the manuals that says (in granite) that some device whose
name doesn't start with NL (like DUA9:) couldn't really be a null device.
How do I find out if a device is definitely a null device?
Thanks
Matt
| T.R | Title | User | Personal
Name | Date | Lines |
|---|
| 656.1 | DT$_NULL is listed in the DCDEF module as well | JON::MORONEY | Question Authority (and the Authorities will question you) | Fri Jan 08 1988 15:01 | 4 |
| I think the null device is defined as DEVCLASS 160 (mailbox device)
and DEVTYPE 3 (NULL). This is what F$GETDVI (and SYS$GETDVI) returns.
-Mike
|
| 656.2 | DEVTYPE and DEVCLASS | MATT::KIRK | Matthew Kirk | Fri Jan 08 1988 15:23 | 1 |
| Thanks! It works.
|