Microsoft KB Archive/110930

= Redirecting Error Messages from Command Prompt: STDERR/STDOUT =

Article ID: 110930

Article Last Modified on 2/20/2007

-

APPLIES TO


 * Microsoft Windows NT Advanced Server 3.1
 * Microsoft Windows NT Workstation 3.1
 * Microsoft Windows NT Advanced Server 3.1
 * Microsoft Windows NT Workstation 3.51
 * Microsoft Windows NT Workstation 4.0 Developer Edition
 * Microsoft Windows XP Professional
 * Microsoft Windows Server 2003, Standard Edition (32-bit x86)
 * Microsoft Windows 2000 Professional Edition

-



This article was previously published under Q110930



SUMMARY
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

Keywords: kbusage KB110930

-

[mailto:TECHNET@MICROSOFT.COM Send feedback to Microsoft]

© Microsoft Corporation. All rights reserved.