How to redirect errors, warnings, debugging or verbose messages to output stream in powershell?
Well, Sometime we dont want to capture output , error, warning, verbose in variable but commands does not support in that case we can use redirection operators to do so.
Streams and piping both are different. When we pipe objects from one cmdlet to another, it pipe only pass value or output of first command to output stream not errors, warnings, debugging messages, or verbose messages along with the objects that it’s designed to process.
So, the pipe operator (|) actually pipes objects down the output stream (stream #1). The receiving cmdlet doesn’t see errors, warnings, verbose messages, or debugging messages, because they’re sent in other streams.
Windows PowerShell also uses the output stream for assignments, like assigning (or saving) a value in a variable.
for example: in below screenshot you can use “=” operator to assign value to $omessage and then you can use it for further operation. since we are using write-output command in below example it send the result to output stream and thats what we can store it to variable which is natural.
What if we re using command which send the the result to verbose stream Ex..
in above example the variable is empty since the command is sending output to verbose stream.
Now what is the solution to redirect the verbose to output stream.. here it is…
How to use redirect combination :
- 2>&1 – Redirect error to Output stream
- 3>&1 – Redirect warning to Output stream
- 4>&1 – Redirect verbose to Output stream
- 5>&1 – Redirect debug to Output stream
- *>&1 – Redirect ALL to Output stream
Windows PowerShell has multiple message streams. The engine sends different types of messages down each stream. As shown in the following image, the streams are parallel, so they don’t interfere with each other.
If you haven’t yet memorized the redirection operators, you can find them in the about_Redirection
