Chinh's semi-random thoughts on software development, gadgets, and other things.

I found out the hard way that mvn (Maven) on Windows always return a success code of true, which means you cannot use the return code ($?) to check whether the mvn command succeeded or failed. Why they decided to break this seemingly basic program contract is a mystery. A work-around is to scan the mvn output and look for specific strings such as “BUILD SUCCESSFUL”.

Here’s how:

function InvokeAndCheckStdOut($cmd, $successString, $failString) {
    Write-Host "====> InvokeAndCheckStdOut"
    $fullCmd = "$cmd|Tee-Object -variable result" 

    Invoke-Expression $fullCmd
    $found = $false
    $success = $false
    foreach ($line in $result) {
      if ($line -match $failString) {
       $found = $true
       $success = $false
       break
      }
      else {
       if ($line -match $successString) {
        $found = $true
        $success = $true
        #"[InvokeAndCheckStdOut] FOUND MATCH: $line"
        break
       }
       else {
        #"[InvokeAndCheckStdOut] $line"
       }
      }
    }

    if (! $success) {
      PlayWav "${env:windir}\Media\ding.wav"
      throw "Mvn command failed."
    }

    Write-Host "InvokeAndCheckStdOut <===="
}

function InvokeMvn($cmd) {
    InvokeAndCheckStdOut $cmd "BUILD SUCCESSFUL" "BUILD FAILED"
}


InvokeMvn "mvn clean install"

See Also

• Tee-Object and Invoke-Expression in PowerShell

The PowerShell Tee-Object Cmdlet allows you to send command output to a file or a variable, and display it in the console at the same time. This is very useful for those instances where you need to parse the text output of a command. I had a hard time getting it to work with Invoke-Expression. After trying different things, I finally found the solution. To get Tee-Object to work with Invoke-Expression in PowerShell 1, include the Tee command in the Invoke-Expression command like this:

Invoke-Expression "mvn clean install | Tee –variable result”

The following, which I guess is what most people try first, doesn’t work (at least in PowerShell V1). I guess because you are storing the result of the “Invoke-Expression” command itself into the variable instead of “mvn clean install”.

    Invoke-Expression "mvn clean install” | Tee -variable result

Wrapping Invoke-Expression in parenthesis (see below) works, but has a drawback: the output is not written to Standard Out until the whole command finishes.

    (Invoke-Expression "mvn clean install”) | Tee -variable result

$tempFile = [IO.Path]::GetTempFileName()

An empty file created immediately when you call this method. Remember to clean it up when are you done!