conditional execution (&& and ||) in powershell

Question

There's already question addressing my issue (Can I get && to work in Powershell?), but with one difference. I need an OUTPUT from both commands. See, if I just run:

(command1 -arg1 -arg2) -and (command2 -arg1)

I won't see any output, but stderr messages. And, as expected, just typing:

command1 -arg1 -arg2 -and command2 -arg1 

Gives syntax error.

Answer 1

2019: the Powershell team are considering adding support for && to Powershell - weigh in at this GitHub PR

Try this:

$(command -arg1 -arg2 | Out-Host;$?) -and $(command2 -arg1 | Out-Host;$?)

The $() is a subexpression allowing you to specify multiple statements within including a pipeline. Then execute the command and pipe to Out-Host so you can see it. The next statement (the actual output of the subexpression) should output $? i.e. the last command's success result.

---

The $? works fine for native commands (console exe's) but for cmdlets it leaves something to be desired. That is, $? only seems to return $false when a cmdlet encounters a terminating error. Seems like $? needs at least three states (failed, succeeded and partially succeeded). So if you're using cmdlets, this works better:

$(command -arg1 -arg2 -ev err | Out-Host;!$err) -and 
$(command -arg1 -ev err | Out-Host;!$err)

This kind of blows still. Perhaps something like this would be better:

function ExecuteUntilError([scriptblock[]]$Scriptblock)
{
    foreach ($sb in $scriptblock)
    {
        $prevErr = $error[0]
        . $sb
        if ($error[0] -ne $prevErr) { break }
    }
}

ExecuteUntilError {command -arg1 -arg2},{command2-arg1}

Answer 2

To simplify multistep scripts where doThis || exit 1 would be really useful, I use something like:

function ProceedOrExit { 
    if ($?) { echo "Proceed.." } else { echo "Script FAILED! Exiting.."; exit 1 } 
}

doThis; ProceedOrExit
doNext

# or for long doos
doThis
ProceedOrExit
doNext

Answer 3

• Bash's / cmd's && and || control operators have NO PowerShell equivalents, and since you cannot define custom operators in PowerShell, there are no good workarounds.

  • The | Out-Host-based workaround in Keith Hill's answer is a severely limited in that it can only send normal command output to the console (terminal), preventing the output from being sent on through the pipeline or being captured in a variable or file.

Find background information in this answer of mine.

Answer 4

The simplest solution is to use

powershell command1 && powershell command2

in a cmd shell. Of course, you can't use this in a .ps1 script, so there's that limitation.

Answer 5

Little longer way is see below

try {
  hostname
  if ($lastexitcode -eq 0) {
    ipconfig /all | findstr /i bios
  }
} catch {
  echo err
} finally {}