Powershell: Equivalent of bash `set -e`

[pauldambra]

I asked this question on twitter and it was suggested I post here.

Many people consider it good practice to start a bash script.

#! /bin/bash
set -eu

set -e tells the script to stop on first error
set -u tells the script to not allow undeclared variables

Although not everyone agrees

I think set -u and Set-StrictMode -Version 1.0 are equivalent.

I just wrote a set of Powershell scripts for managing an elasticsearch server. Then a few top-level scripts to tie them together.

It would have been really useful to be able to write something equivalent to...

set -e

$someValue = .\server-task-1.ps1
.\server-task-2.ps1 -using $someValue
.\task-that-requires-everything-else-suceeded.ps1

... but I couldn't find how to and ended up with something more like...

$someValue = .\server-task-1.ps1
if ($LastExitCode -ne 0) {
    exit $LastExitCode 
}

.\server-task-2.ps1  -using $someValue
if ($LastExitCode -ne 0) {
    exit $LastExitCode 
}

.\task-that-requires-everything-else-suceeded.ps1
if ($LastExitCode -ne 0) {
    exit $LastExitCode 
}

Apologies if this is already possible and I've missed it...

[SteveL-MSFT]

$erroractionpreference = "stop" is similar to set -e, except it only works against cmdlets and not native commands

[pauldambra]

As someone fresh to Powershell that's a confusing distinction.

So would $erroractionpreference = "stop" work for my example above..?

i.e.

$erroractionpreference = "stop"

$someValue = .\server-task-1.ps1

# does not run the next two commands if server-task-1.ps1 exits with code != 0
.\server-task-2.ps1 -using $someValue
.\task-that-requires-everything-else-suceeded.ps1

but

$erroractionpreference = "stop"

$someValue = .\server-task-1.exe

# does run the next two commands _even though_ server-task-1.exe exits with code != 0
.\server-task-2.ps1 -using $someValue
.\task-that-requires-everything-else-suceeded.ps1

[SteveL-MSFT]

$erroractionpreference = "stop" only works if Write-Error is called (such as an exception is raised). It doesn't do any checks against $lastexitcode. We can certainly look into adding another preference variable to throw an exception if $lastexitcode != 0.

[mopadden]

Would probably want to throw the exception only in a context where Powershell also sets $? to false as a result.

Throwing an exception in other situations where lastexitcode != 0 would not give a result equivalent to "set -e" in bash.

https://www.gnu.org/software/bash/manual/html_node/The-Set-Builtin.html
Edit: the idea is to throw an error on failure where the success/failure of an application is not tested.

[mopadden]

Hi, i've done some work on this, can I ask for an assignment?

[SteveL-MSFT]

@mopadden consider it assigned, GitHub doesn't allow assigning to people without write access

[SteveL-MSFT]

Assigning to @daxian-dbw who's assigned to the PR so no one else duplicates this work

[SteveL-MSFT]

Anyone who's interested in this should review the RFC: https://github.com/PowerShell/PowerShell-RFC/pull/88/files

[choovick]

+1, very inconvenient to check $LastExitCode, especially when using PS for build scripts with multiple steps...