PowerShell cmdLet Start-Job

Passing variables to a job

In order to pass a variable to a script block that is started with start-job, the variable name needs to be prefixed with using:.

$var=42

$scriptBlock = { add-content ~/variable-value "var=$var | using:var=$using:var" }

$var='changed'

start-job $scriptBlock

Github repository about-PowerShell, path: /cmdlets/job/start/pass-variable.ps1

This script, when run, writes the following line into ~/variable-value:

var= | using:var=changed

Working directory for jobs ps-start-job-wd

A job's working directory is set to $home\Documents (Windows Powershell) or $home (PowerShell Core).

This is demonstrated by the following simple pipeline: it starts a job with a script block which in turn writes the current location (get-location) to ~/current-directory.

After the job has finished, ~/current-directory can be inspected to determine the current directory of powershell jobs.

start-job { add-content ~/current-directory (get-location) }

Github repository about-PowerShell, path: /cmdlets/job/start/current-directory.ps1

PowerShell 7 finally comes with the new option -workingDirectory which allows to change the initial working directory for a background job.

Passing parameters to a scheduled cmdLet

The following command tries to use start-job to schedule a download of a resource and storing it to an aribitrary file, using the -outFile parameter:

start-job invoke-webRequest http://server.xyz/path/to/resource.pdf -outFile downloadedFile.pdf

However, this results in the error message Start-Job : Parameter set cannot be resolved using the specified named parameters. This is becouse start-job (rather than invoke-webRequest) tries to interprete the -outfile parameter.

In order to pass a parameter to a scheduled cmdLet, a script block must be used:

start-job -scriptBlock { invoke-webRequest http://server.xyz/path/to/resource.pdf -outFile downloadedFile.pdf }

The -scriptBlock parameter is not necessary:

start-job { invoke-webRequest http://server.xyz/path/to/resource.pdf -outFile downloadedFile.pdf }

Of course, if using a script block to download a resource, absolute paths or the working directory should be specifed in order to download the file to a non-default location.

The following command combines the using scope with the $pwd automatic variable to download a resource to the current directory:

start-job  { invoke-webRequest https//server.xyz/path/to/resource.pdf -outFile $using:pwd\downloadedFile.pdf }

PowerShell cmdLet Start-Job

Passing variables to a job

Working directory for jobs ps-start-job-wd

Passing parameters to a scheduled cmdLet

See also