parse error in one-line powershell script

Question

I am trying to create a one-line powershell script that just requests an url. The script is working fine when I run it as a ps1 file:

File "test.ps1":

$webclient=New-Object "System.Net.WebClient"
$data=$webclient.DownloadString("https://google.com")

I run this script in PS console like this:

PS C:\test.ps1 -ExecutionPolicy unrestricted

This runs without any problem, but when I try to schedule this script and make it a one-line according to these recommendations i.e. replace "" with '' and separate commands with ; so the result will be:

one-line:

powershell -ExecutionPolicy unrestricted -Command "$webclient=New-Object 'System.Net.WebClient'; $data=$webclient.DownloadString('https://google.com');"

Then I got the following problem:

Error:

The term '=New-Object' is not recognized as the name of a cmdlet, function, script file, or operable program

I tried another script that also works fine as ps1 file, but not working as one-liner:

$request = [System.Net.WebRequest]::Create("https://google.com")
$request.Method = "GET"
[System.Net.WebResponse]$response = $request.GetResponse()
echo $response

one-line:

powershell -ExecutionPolicy unrestricted -Command "$request = [System.Net.WebRequest]::Create('https://google.com'); $request.Method = 'GET'; [System.Net.WebResponse]$response = $request.GetResponse(); echo $response"

Error:

Invalid assignment expression. The left hand side of an assignment operator needs to be something that can be assigned to like a variable or a property. At line:1 char:102

According to get-host command I have powershell v 2.0. What is the problem with one-line scripts above?

@AnsgarWiechers Thanks, but unfortunately call operator (&) did not help me in this case, I get the same errors :/ — Andrey Prokhorov
– Andrey Prokhorov, Commented Jan 13, 2017 at 13:07
That's because you're running the commandline from PowerShell instead of running it as a scheduled task like you said. If you need to run it from an interactive console use CMD to emulate an environmnent that's more similar to what you have with a scheduled task. — Ansgar Wiechers
– Ansgar Wiechers, Commented Jan 13, 2017 at 13:15
Yes, you are right! It was not working in powershell but do works in cmd. I thought it does not matter where to test the script. Thank you so much! Copy your first comment as answer if you want me to mark this question as solved. — Andrey Prokhorov
– Andrey Prokhorov, Commented Jan 13, 2017 at 13:19

Ansgar Wiechers · Accepted Answer · 2017-01-13 13:59:34Z

2

Put the statements you want to run in a scriptblock and run that scriptblock via the call operator:

powershell.exe -Command "&{$webclient = ...}"

Note that pasting this commandline into a PowerShell console will produce a misleading error, because PowerShell (the one into which you paste the commandline) expands the (undefined) variables in the string to null values, which are then auto-converted to empty strings. If you want to test a commandline like this, run it from CMD, not PowerShell.

It might also be a good idea to have the scriptblock exit with a status code, e.g.

&{...; exit [int](-not $?)}

or

&{...; $status=$response.StatusCode.value__; if ($status -eq 200) {exit 0} else {exit $status}}

answered Jan 13, 2017 at 13:59

Ansgar Wiechers

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3 Comments

mklement0 Over a year ago

Good advice and explanation, but do you know why the OP's attempt didn't work, why the use of a script block is necessary? It seems to me that the OP's problems only stemmed from running the commands in PS, where the premature variable expansion you describe occurred.

Ansgar Wiechers Over a year ago

@mklement0 The error was indeed caused by pasting the commandline with the double-quoted string into PowerShell. I think using &{...} was required if you wanted to run more than one statement with PowerShell v2, but I can't vouch for that. If it was, it doesn't seem to be required with more recent versions anymore, but I don't know when exactly that was changed, and I prefer using the scriptblock wrapper anyway, just to be on the safe side.

Andrey Prokhorov Over a year ago

For those of you who got SSL error when running the script above - check the answer stackoverflow.com/a/9918045/2021224, just adding a line "[System.Net.ServicePointManager]::ServerCertificateValidationCallback = {$true}" helped me to reach the goal.

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