Redirecting Error Messages from Command Prompt: STDERR/STDOUT

Last reviewed: May 14, 1997
Article ID: Q110930

The information in this article applies to:

Microsoft Windows NT operating system version 3.1
Microsoft Windows NT Advanced Server version 3.1

When redirecting output from an application using the ">" symbol, error messages still print to the screen. This is because error messages are often sent to the Standard Error stream instead of the Standard Out stream.

Output from a console (Command Prompt) application or command is often sent to two separate streams. The regular output is sent to Standard Out (STDOUT) and the error messages are sent to Standard Error (STDERR). When you redirect console output using the ">" symbol, you are only redirecting STDOUT. In order to redirect STDERR you have to specify "2>" for the redirection symbol. This selects the second output stream which is STDERR.

EXAMPLE

The command "dir file.xxx" (where file.xxx does not exist) will display the following output:

   Volume in drive F is Candy Cane
   Volume Serial Number is 34EC-0876

   File Not Found

If you redirect the output to the NUL device using "dir file.xxx > nul", you will still see the error message:

   File Not Found

To redirect the error message to NUL, use the following command:

   dir file.xxx 2> nul

Or, you can redirect the output to one place, and the errors to another.

   dir file.xxx > output.msg 2> output.err

You can print the errors and standard output to a single file by using the "&1" command to redirect the output for STDERR to STDOUT and then sending the output from STDOUT to a file:

   dir file.xxx 1> output.msg 2>&1

Additional query words: prodnt pipe UNIX stdin re-directed
Keywords : kbusage nthowto
Version : 3.1
Platform : WINDOWS

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Last reviewed: May 14, 1997
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