PowerShell/CrashCourse.md

# PowerShell Scripting Crash Course

After having followed the [README.md](./README.md), `.ps1` scripts in the same folder as `$PROFILE.CurrentUserAllHosts` will be available in `$env:PATH` globally:

```powershell
# Open the $PROFILE folder
explorer (Split-Path -Parent $PROFILE.CurrentUserAllHosts)
codium (Split-Path -Parent $PROFILE.CurrentUserAllHosts)
# Or start directly editing a script
notepad "$(Split-Path -Parent $PROFILE.CurrentUserAllHosts)\my-script.ps1"
codium "$(Split-Path -Parent $PROFILE.CurrentUserAllHosts)\my-script.ps1"
```

# variables

[PowerShell is as case-insensitive as possible.](https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_case-sensitivity?view=powershell-7.3) This means `$MyInvocation` works just the same as `$mYinoCAtiOn` among other things. Coming from a Unix background and preferring some consistency I like to pretend it is case-sensitive so in this repo I'll strive for that but it's worth keeping in mind. Especially since the Microsoft docs use case a lot in variable and cmdlet names.

Variables use `$` to distinguish themselves and can be set with `=`

```powershell
$a_variable = "this one is a string"
$interpolate_a_string = "like this: $a_variable"
```

## booleans

There are a few constants to know: `$true`, `$false`, `$null`. Empty strings (`""`, `''`), `$null` and `0` evaluate as `$false`

# if and while

There are a handful of [comparison operators](https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_comparison_operators?view=powershell-7.3) which can be used with `if` or `while` like this:

```powershell
if ($val -eq "y") {
  Write-Host "value is a y"
}
else {
  Write-Host "value is not a y"
}

while ($num -lt 50) {
  $num = $num + 1
}
```

# param

At the beginning of scripts and functions `param` list can be specified like this

```powershell
param(
  [string]$name = "Anonymous",
  [int]$age,
  [switch]$silent
)
```

There are [a lot of different powers](https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_functions_advanced_parameters?view=powershell-7.3) behind the square bracket syntax, [including custom validation](https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_functions_advanced_parameters?view=powershell-7.3#validatescript-validation-attribute), but these are the basics. Parameters are not mandatory by default use `[Parameter(Mandatory)]` for that. The above param block could be used in a script like this:

```powershell
if ($silent) { exit }
Write-Host "Hello $name"
if ($age) {
  Write-Host "according to the -age you provided you are: $age"
}
```

And run like this:

```powershell
name_and_age.ps1 -name "Rose" -age "27"
# or, arguments are also positional!
name_and_age.ps1 "Rose" "27"
```

# functions

Functions use `param` too (instead of parenthesis like other languages). The last value is the `return` result, (which you can also use to `return` early... or just regularly if you want)

```powershell
function My-Add {
  param(
    [Parameter(Mandatory)][int]$x,
    [Parameter(Mandatory)][int]$y,
  )

  $x + $y
}
```

# For and ForEach

# Paths and Items

# See Also

- [About scripts (learn.microsoft.com)](https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_scripts?view=powershell-7.3)