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Q82216: Command Piped in Root Directory May Hang Machine

Article: Q82216
Product(s): Microsoft Disk Operating System
Version(s): MS-DOS:5.0,5.0a,6.0,6.2,6.21,6.22; WINDOWS:3.0,3.0a,3.1,3.11
Operating System(s): 
Keyword(s): 
Last Modified: 19-NOV-1999

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The information in this article applies to:

- Microsoft MS-DOS operating system versions 5.0, 5.0a, 6.0, 6.2, 6.21, 6.22 
- Microsoft Windows versions 3.0, 3.0a, 3.1, 3.11 
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SYMPTOMS
========

If you run an MS-DOS command in a root directory that contains the maximum
allowable number of directory entries, and redirect the output by using a pipe
character (|), your system may stop responding (hang).

CAUSE
=====

MS-DOS provides the means to direct the output of one command as input to
another using a redirection technique known as "piping." Because MS-DOS is a
single-tasking environment, these pipes are created via temporary files on
disk.

MS-DOS checks for the presence of an environment variable called TEMP specifying
the drive and directory where such temporary files should be placed. If no TEMP
variable or directory exists, MS-DOS uses the current directory.

If the output from one command is piped to another when the current directory is
a root directory that already contains the maximum number of directory entries
(for example, 512 files for fixed disks,) the inability to create the temporary
files may stop (hang) the machine.

RESOLUTION
==========

To eliminate this problem, do the following:

- Delete or move some files from the root directory to create space for
  additional directory entries.

-or-

- Create an X:\TEMP directory and place a SET TEMP=X:\TEMP statement in the
  AUTOEXEC.BAT file. The temporary files created by the pipe are then placed in
  the X:\TEMP directory, where X: is a valid MS-DOS logical drive.

STATUS
======

Microsoft has confirmed this to be a problem in MS-DOS. We are researching this
problem and will post new information here as it becomes available.

REFERENCES
==========

For additional information on command redirection, refer to the "Microsoft
MS-DOS User's Guide and Reference," for version 5.0.

For additional information on the limits of the root directory with regard to the
number of directory entries, query on the following words in the Microsoft
Knowledge Base:

  " directory and limit and entries " (without the quotation marks)

Additional query words: 6.22 5.00 5.00a 6.00 6.20 lock up lockup 3.00 3.00a 3.10 3.11

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Keywords          :  
Technology        : kbWin3xSearch kbZNotKeyword3 kbWin300 kbWin300a kbWin310 kbWin311 kbMSDOSSearch kbMSDOS621 kbMSDOS622 kbMSDOS620 kbMSDOS600 kbMSDOS500 kbMSDOS500a
Version           : MS-DOS:5.0,5.0a,6.0,6.2,6.21,6.22; WINDOWS:3.0,3.0a,3.1,3.11

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