Here are two separate issues when using IF EXIST ?:\NUL. I'm lazy and wrote up a info text file over at https://fd.lod.bz/redist/testing/devNUL/ that I will just paste in here. The test batch and result files referenced in the text can be found there as well.
Although this behavior deviates from that of other drives,it is
consistent with the behavior of MS-DOS 6.22 using MSCDEX. There is
the possibility that correcting this issue has the potential to break
compatibility with any program that may rely on this behavior.
Issue 2:
Testing for the existence of a non-existing drive returns unreliable
results. This seems reproducible based on the current working directory
when the test is performed. For each test, a copy of the test.bat was
placed in the current working directory.
result0.htm was run with the current drive and directory on an internal
local drive (C:). It incorrectly shows that the non-existing drive (P:)
was found.
result1.htm was run with the current drive and directory on an remote
network share (N:). It correctly shows that the non-existing drive (P:)
was not found.
Switching back and forth between drive C: and N: and running the
TEST.BAT consistently produces the same results.
Hi,
Here are two separate issues when using
IF EXIST ?:\NUL. I'm lazy and wrote up a info text file over at https://fd.lod.bz/redist/testing/devNUL/ that I will just paste in here. The test batch and result files referenced in the text can be found there as well.NUL Device Existence Test
https://fd.lod.bz/redist/testing/devNUL/ 2023-05-23
This test reveals two separate issues:
Issue 1:
Testing for the existence of a path by using the
NULdevice does not work on CD/DVD drives or Network Shares. The result is always FALSE.IF EXIST N:\NUL ECHO Drive N: exists.See either result0.htm or result1.htm.
Although this behavior deviates from that of other drives,it is consistent with the behavior of MS-DOS 6.22 using MSCDEX. There is the possibility that correcting this issue has the potential to break compatibility with any program that may rely on this behavior.
Issue 2:
Testing for the existence of a non-existing drive returns unreliable results. This seems reproducible based on the current working directory when the test is performed. For each test, a copy of the test.bat was placed in the current working directory.
result0.htm was run with the current drive and directory on an internal local drive (C:). It incorrectly shows that the non-existing drive (P:) was found.
result1.htm was run with the current drive and directory on an remote network share (N:). It correctly shows that the non-existing drive (P:) was not found.
Switching back and forth between drive C: and N: and running the TEST.BAT consistently produces the same results.