Redirecting error messages from Command Prompt: STDERR/STDOUT
This article describes redirecting error messages from Command Prompt.
Original product version: Visual C++
Original KB number: 110930
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 that is STDERR.
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