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README.md

PowerShell knowledge

Useful notions and examples for Windows PowerShell and PowerShell "Core" (pwsh).

Snippets

Setup allowed web security protocols

This only allows Tls12 and Tls13 connections.

It is best to put this command also in your $PROFILE file.

  • Tls 1.0 and Tls 1.1 are deprecated as of RFC 8996 id est March 2021
  • All SSL versions are deprecated as of RFC 7568 id est June 2015
[System.Net.ServicePointManager]::SecurityProtocol = [System.Net.SecurityProtocolType]'Tls12,Tls13'
# or a bit shorter
[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]'Tls12,Tls13'

List user sessions

From: https://stackoverflow.com/a/66851552/9156059

Get-CimInstance -ClassName Win32_LogonSession | Get-CimAssociatedInstance -Association Win32_LoggedOnUser

List SSH sessions

From: https://stackoverflow.com/a/66851552/9156059

Get-CimInstance -ClassName Win32_Process -Filter "Name = 'sshd.exe'" | Get-CimAssociatedInstance -Association Win32_SessionProcess | Get-CimAssociatedInstance -Association Win32_LoggedOnUser | Where-Object {$_.Name -ne 'SYSTEM'}

Run a remote (online) script, version 1

NB: the version #2 of this script is preferred; see why below.

Also see snippets:

# short version one-liner:
$u = 'https://cdn.jsdelivr.net/gh/aetonsi/misc/scripts/setup-gitbash-environment/main.ps1'; irm $u | iex
# extended version one-liner:
$URL = 'https://cdn.jsdelivr.net/gh/aetonsi/misc/scripts/setup-gitbash-environment/main.ps1'; Invoke-RestMethod $URL | Invoke-Expression

Run a remote (online) script, version 2

This script respects any #Requires directive and removes the need for any check about administrator privileges and whatnot.

Also see snippets:

# short version one-liner:
$u = 'https://cdn.jsdelivr.net/gh/aetonsi/misc/scripts/setup-gitbash-environment/main.ps1'; [Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]'Tls12,Tls13'; Set-ExecutionPolicy b -s p -f; irm $u > ($f = "$([IO.Path]::GetTempPath())$([GUID]::NewGuid()).ps1"); & $f; ri $f -f
# extended version one-liner:
$URL = 'https://cdn.jsdelivr.net/gh/aetonsi/misc/scripts/setup-gitbash-environment/main.ps1'; [Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]'Tls12,Tls13'; Set-ExecutionPolicy Bypass -Scope Process -Force; Invoke-RestMethod $URL > ($File = "$([System.IO.Path]::GetTempPath())$([GUID]::NewGuid()).ps1"); & $File; Remove-Item $File -Force
# extended version line by line:
$URL = 'https://cdn.jsdelivr.net/gh/aetonsi/misc/scripts/setup-gitbash-environment/main.ps1'
[System.Net.ServicePointManager]::SecurityProtocol = [System.Net.SecurityProtocolType]'Tls12,Tls13'
Set-ExecutionPolicy Bypass -Scope Process -Force
Invoke-RestMethod $URL > ($File = "$([System.IO.Path]::GetTempPath())$([GUID]::NewGuid()).ps1")
& $File
Remove-Item $File -Force

Alternative script download method

This replaces irm/Invoke-RestMethod.

([System.Net.WebClient]::New()).DownloadString($URL)
# or a bit shorter
([Net.WebClient]::New()).DownloadString($URL)

Select-Object with custom expression

Get-Process |
    Select-Object -First 10 id,
        processname,
        @{label = 'ExecutableType'; expression = { [System.IO.Path]::GetExtension($_.Path) } },
        path |
    Format-Table

switch with complex expressions

This reverse switch works in almost every language (at least those with c-like syntax).

switch ($true) {
    (($PSVersionTable.PSEdition -eq 'Core') -and ($PSVersionTable.PSVersion -ge 7)) { Write-Output "it's pwsh >= 7.x" ; break }
    (($PSVersionTable.PSEdition -eq 'Core') -and ($PSVersionTable.PSVersion -lt 7)) { Write-Output "it's pwsh 6.x" ; break }
    ($PSVersionTable.PSEdition -eq 'Desktop') { Write-Output "it's winposh" ; break }
    ($true) { "it's true" }
    default { Write-Output 'else' }
}

Debug breakpoints

Run man about_Debuggers for information about debugging.

The following is a simple setup to trigger a debug session from within a script, like php's xdebug_break(), then allow for fiddling with the current powershell session. You can even access the session's variables current values. This session is more or less equivalent to running a powershell script with the -noexit argument, except that you can use this method in the middle of a script.

### debug-helper.ps1

# define once, then SOURCE the script (see below)
function debug_break() {}
function debug_breakpoints_setup() {
    Get-PSBreakpoint | Remove-PSBreakpoint
    Set-PSBreakpoint -Command debug_break >$null
}
### some-script.ps1

# call at the start of each script
. ./debug-helper.ps1 # dot-source the script (man about_Scripts); if importing a module instead, the debug session will not have access to the current scope
debug_breakpoints_setup

# ... your script ...
$xxx = Get-Random -Minimum 0 -Maximum 1000
Write-Output "`$xxx = $xxx"
debug_break # this effectively starts the debug session here; you can test and access $xxx inside the session
Write-Output "after debug"
# ...

You can then use hotkeys to control the debug session (run ? in a debug session for more info):

  • c: continues execution until the next breakpoint
  • s: steps into the next statement then stops
  • v: steps over the next statement, skipping invocations, then stops
  • k: displays current call stack
  • q: stops the script execution, like an Exit statement
  • ?: display debugging help