NOVELL TECHNICAL BULLETIN

           TITLE:  Using IF EXIST...NUL on Network Drives
    DOCUMENT ID#:  TB.P.300
            DATE:  3 March 1992
         PRODUCT:  NetWare, DOS
PRODUCT REVISION:  All
      SUPERSEDES:  N/A

         SYMPTOM:  Incorrect results when using IF EXIST with the
                   NUL operator on a network drive. 

ISSUE/PROBLEM

Users have reported incorrect results when using the IF EXIST batch
file command with the NUL operator to determine whether a directory
exists on a network drive.  An example of this command is IF EXIST
F:\TEST\91\NUL.  The error occurs because the NetWare shell sees
NUL as a DOS device instead of a filename.  As a result, it passes
the command to DOS, which does not recognize the network drive (F:
in the example above).  DOS then ignores the command and returns an
exit code of 0 (success). 

Using the above IF EXIST command on a local drive (for example, IF
EXIST C:\TEST\91\NUL) poses no problem to the user, and the
appropriate status is returned. 

SOLUTION

There are two possible workarounds to this problem.

The first is to use *.* in place of the NUL operator in the IF
EXIST statement.  This is 100% effective as long as the directory
in question is not empty.

Users may, as an alternate workaround, redesign their batch file
approach to avoid the above limitations.

Novell Engineering has determined that in order to address this
anomaly (which occurs in the client between DOS and certain shell
device drivers), significant re-engineering of the shell would be
necessary.  This would lead to a drastic increase in the size of
the shell.  Since such an increase is an unacceptable solution, the
user should implement one or both of the two workarounds above.