Pipe (|) After IF EXIST Fails (74464)

The information in this article applies to:
    Microsoft MS-DOS operating system 5.0
    Microsoft MS-DOS operating system 5.0a
    Microsoft MS-DOS operating system 6.0
    Microsoft MS-DOS operating system 6.2
    Microsoft MS-DOS operating system 6.21
    Microsoft MS-DOS operating system 6.22

This article was previously published under Q74464


There is a known problem with the pipe (|) command that causes the pipe to fail when used after an IF EXIST statement. For example, the command

IF EXIST c:\dos\readme.txt TYPE c:\dos\readme.txt | MORE

normally displays the contents of C:\DOS\README.TXT one screen at a time. When this command is issued under MS-DOS 5.0, 6.0, or 6.2 no information is displayed and you are returned to the prompt, even though the file exists.

In addition, this command results in File Allocation Table (FAT) corruption on the drive that the TEMP environment variable is pointing to or on the current drive if no TEMP variable has been set. Running CHKDSK after this command shows there are "<x> lost clusters in 1 chain," where <x> is dependent upon the size of the file being processed by the pipe. (The number of lost clusters and chains might be larger if there was additional FAT corruption prior to using the pipe.) The FAT corruption caused by this command does not result in data loss, and you can use CHKDSK with the /F switch to correct the corruption.

Please refer to the "Microsoft MS-DOS User's Guide and Reference" for more information on the use of the CHKDSK command.

Microsoft has confirmed this to be a problem in MS-DOS versions 5.00, 5.00a, 6.00, 6.20, 6.21, and 6.22. We are researching this problem and will post new information here as it becomes available.

Modification Type: Major Last Reviewed: 5/10/2003
Keywords: KB74464