CODEWITHSUNDEEP
powershell
Avinash Ganesh
Avinash Ganesh

Reputation: 453

How to capture error messages thrown by a command?

I am writing a PowerShell script where in I need to capture the error message that it's throwing. Note: according to PowerShell, there is no error and command is executed successfully.

For example: I tried to download a package from SVN Link. The Link actually is not present. The script is showing me error message on the console. However, when I tried to check $_ or $? or $error, I did not see any error message. However, $LASTEXITCODE returned value 1. I need to get the exact error message.

Upvotes: 12

Views: 64299

Answers (3)

Ansgar Wiechers
Ansgar Wiechers

Reputation: 200233

If you get an error message, you need to capture the error stream:

$msg = command 2>&1

or

command 2>error.txt

PowerShell writes its messages to different streams that can be redirected to files for capturing the respective output.

  • Stream 1 (default): regular output ("STDOUT")
  • Stream 2: error messages ("STDERR"), including error messages from external programs
  • Stream 3: warning messages
  • Stream 4: verbose messages
  • Stream 5: debug messages
  • Stream 6: information messages (only PowerShell v5 and newer)

To capture a particular stream in a file you need to redirect the stream number to a file name. For instance

command 2>"C:\path\to\error.log"

would capture all error messages produced by command in the file C:\path\to\error.log. Use 2>> instead of 2> if you want to append to the file instead of overwriting it with each run.

You can also combine other streams with STDOUT to process/redirect all command output:

command >>"C:\path\to\all.log" *>&1

See Get-Help about_Redirection or this Scripting Guy article for more information about streams and redirection.

Things worth of note:

  • The *> redirection was introduced with PowerShell v3, hence it won't work in PowerShell v2 and earlier.
  • PowerShell v5 introduced a new stream (Information, stream number 6) since people kept misusing Write-Host because they didn't understand what the cmdlet was intended for.

Upvotes: 35

Bruno Zell
Bruno Zell

Reputation: 8541

Inspired by David Brabants answer, you can combine both stdout and stderr into one string array using this command:

$output = [string[]] (.\Cli.exe -p $param 2>&1)

It will execute Cli.exe with the parameter p. This is optionally.

Clarification

2>&1 means the stream #2 (stderr) will be redirected to stream #1 (stdout), thus both streams will arrive in $output.

Upvotes: 2

David Brabant
David Brabant

Reputation: 43489

Assuming your executable is named svn.exe and is on the path, you can capture the messages it sends to console this way:

$msg = [string] (svn.exe <your parameters here>)

You can then parse the $msg string to find information you need.

Upvotes: 6

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