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From Ben Hyde <bh...@gensym.com>
Subject MSDOS File System Curiosities
Date Wed, 06 May 1998 16:04:15 GMT
There is a great many pages in the "developer's network" CD about these
filenames.

Approximately one for every application MS has ever made that attempts
to explain
why something seems broken as a result of this.  The following is
typical:
---
If you search for a file in the Microsoft Windows File Manager program,
using some MS-DOS reserved words with the File Search command, File
Manager finds those reserved word in all directories because MS-DOS
character devices are defined as files in all directories. This is
standard MS-DOS behavior. 

Examples of MS-DOS reserved words are: 
   CON   COM1 - COM4
   PRN   AUX    LPT1
---
It's particularly obnoxious that they say "examples"   I believe this is
the complete
list, but I'm not sure.  The note this a longer list.
   CON     Keyboard and display
   PRN     System list device, usually a parallel port
   AUX     Auxiliary device, usually a serial port
   CLOCK$  System real-time clock
   NUL     Bit-bucket device
   A:-Z:   Drive letters
   COM1    First serial communications port
   LPT1    First parallel printer port
   LPT2    Second parallel printer port
   LPT3    Third parallel printer port
   COM2    Second serial communications port
   COM3    Third serial communications port
   COM4    Fourth serial communications port

It maybe this is the whole list, or that it is in fact all devices that
are character based, or WHO KNOWS!

One note suggests looking at memory around 0070 to find this list.
  > debug
  -  d 0070:0000
  0070:0000  E9 6D 03 A7 00 EA FD 02-70 00 00 00 00 FF AF 00
.m......p.......
  0070:0010  DC 02 87 DB 00 32 20 00-94 03 A7 00 00 00 00 00   .....2
.........
  0070:0020  00 00 E8 00 36 00 70 00-13 80 EC 01 F7 01 43 4F
....6.p.......CO
  0070:0030  4E 20 20 20 20 20 48 00-70 00 00 80 EC 01 18 02   N
H.p.......
  0070:0040  41 55 58 20 20 20 20 20-5A 00 70 00 C0 A8 EC 01   AUX
Z.p.....
  0070:0050  FC 01 50 52 4E 20 20 20-20 20 6C 00 70 00 08 80   ..PRN
l.p...

To add to my confusion there is a note about how to delete such files
under NT,
so it must be possible for them to exist.  It recomends (I love this) rm
from the
posix tools.  Which opens the possiblity that this is all a mute point
within the
"posix" subsystem.

In summary I suspect that taking the list above and declining to handle
any
of those, i.e. not LPT3 or LPT3.* we are pretty safe.   I'm not
preparing a 
patch, I'm just reading the "doc."

  - ben






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