What is shortest possible way to download script from HTTP and run it with parameters using Powershell? - powershell

Question

I have a PowerShell script file stored in an internal artifact server. The script URL is http://company-server/bootstrap.ps1.
What is a concise way to download that script and execute with a custom parameter?
I want to send such a command to users, who will copy-paste it over and over, so it must be a single-line and should be short.
What I currently have works, but it is long and unwieldy:
$c=((New-Object System.Net.WebClient).DownloadString('http://company-server/bootstrap.ps1'));Invoke-Command -ScriptBlock ([Scriptblock]::Create($c)) -ArgumentList 'RunJob'
I am wondering if there is shorter way to do this.

Answer 1

Note: From a code golf perspective, the solutions below could be shortened further, by eliminating insignificant whitespace; e.g., &{$args[0]}hi instead of & { $args[0] } hi. However, in the interest of readability such whitespace was kept.
A short formulation of a command that downloads a script via HTTP and executes it locally, optionally with arguments is probably this, taking advantage of:
alias irm for Invoke-RestMethod, in lieu of (New-Object System.Net.WebClient).DownloadString()
omitting quoting where it isn't necessary
relying on positional parameter binding
& ([scriptblock]::Create((irm http://company-server/bootstrap.ps1))) RunJob
RunJob is the OP's custom argument to pass to the script.
An even shorter, but perhaps more obscure approach is to use iex, the built-in alias for Invoke-Expression, courtesy of this GitHub comment.
iex "& { $(irm http://company-server/bootstrap.ps1) } RunJob"
As an aside: in general use, Invoke-Expression should be avoided.
The command uses an expandable string ("...", string interpolation) to create a string with the remote script's content enclosed in a script block { ... }, which is then invoked in a child scope (&). Note how the arguments to pass to the script must be inside "...".
However, there is a general caveat (which doesn't seem to be a problem for you): if the script terminates with exit, the calling PowerShell instance is exited too.
There are two workarounds:
Run the script in a child process:
powershell { iex "& { $(irm http://company-server/bootstrap.ps1) } RunJob" }
Caveats:
The above only works from within PowerShell; from outside of PowerShell, you must use powershell -c "..." instead of powershell { ... }, but note that properly escaping embedded double quotes, if needed (for a URL with PS metacharacters and/or custom arguments with, say, spaces), can get tricky.
If the script is designed to modify the caller's environment, the modifications will be lost due to running in a child process.
Save the script to a temporary file first:
Note: The command is spread across multiple lines for readability, but it also works as a one-liner:
& {
$f = Join-Path ([IO.Path]::GetTempPath()) ([IO.Path]::GetRandomFileName() + '.ps1');
irm http://company-server/bootstrap.ps1 > $f;
& $f RunJob;
ri $f
}
The obvious down-side is that the command is much longer.
Note that the command is written with robustness and cross-platform compatibility in mind, so that it also works in PowerShell Core, on all supported platforms.
Depending on what platforms you need to support / what assumptions you're willing to make (e.g., that the current dir. is writeable), the command can be shortened.
Potential future enhancements
GitHub issue #5909, written as of PowerShell Core 6.2.0-preview.4 and revised as of PowerShell Core 7.0, proposes enhancing the Invoke-Command (icm) cmdlet to greatly simplify download-script-and-execute scenarios, so that you could invoke the script in question as follows:
# WISHFUL THINKING as of PowerShell Core 7.0
# iwr is the built-in alias for Invoke-WebRequest
# icm is the built-in alias for Invoke-Command.
iwr http://company-server/bootstrap.ps1 | icm -Args RunJob
GitHub issue #8835 goes even further, suggesting an RFC be created to introduce a new PowerShell provider that allows URLs to be used in places where only files were previously accepted, enabling calls such as:
# WISHFUL THINKING as of PowerShell Core 7.0
& http://company-server/bootstrap.ps1 RunJob
However, while these options are very convenient, there are security implications to consider.

Answer 2

Here is a shorter solution (158 chars.)
$C=(New-Object System.Net.WebClient).DownloadString("http://company-server/bootstrap.ps1");icm -ScriptBlock ([Scriptblock]::Create($c)) -ArgumentList "RunJob"
Here is 121
$C=(curl http://company-server/bootstrap.ps1).content;icm -ScriptBlock ([Scriptblock]::Create($c)) -ArgumentList "RunJob"
Here is 108
$C=(curl http://company-server/bootstrap.ps1).content;icm ([Scriptblock]::Create($c)) -ArgumentList "RunJob"
Here is 98
$C=(iwr http://company-server/bootstrap.ps1).content;icm -sc([Scriptblock]::Create($c)) -ar RunJob
Thanks to Ansgar Wiechers