Powershell – How to capture error output only in a variable in PowerShell

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I want to store the stderr output of a PowerShell command in a variable. I don't want to store it in a file and I don't want standard output included, just the error output.

This redirects to a file named error.txt:

& $command $params 2> error.txt

This redirects both stderr and stdout to the $output variable:

$output = & $command $params 2>&1

But I want to store only the error output in a variable (the same as the content of the error.txt file above), without writing anything to file. How do I do that?

Best Answer

You can call the command a slightly different way and use the -ErrorVariable parameter in PowerShell:

Invoke-Expression "$command $params" -ErrorVariable badoutput

$badoutput will now contain the contents of the error string.

Related Solutions

Windows – Setting Windows PowerShell environment variables

If, some time during a PowerShell session, you need to append to the PATH environment variable temporarily, you can do it this way:

$env:Path += ";C:\Program Files\GnuWin32\bin"

If you need your path to be called before standard one, insert it at the beginning

$env:Path = "C:\Program Files\GnuWin32\bin;$env:Path"

Bash – Pipe output and capture exit status in Bash

There is an internal Bash variable called $PIPESTATUS; it’s an array that holds the exit status of each command in your last foreground pipeline of commands.

<command> | tee out.txt ; test ${PIPESTATUS[0]} -eq 0

Or another alternative which also works with other shells (like zsh) would be to enable pipefail:

set -o pipefail
...

The first option does not work with zsh due to a little bit different syntax.

Best Answer

Related Solutions

Windows – Setting Windows PowerShell environment variables

Bash – Pipe output and capture exit status in Bash

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