131 lines
4.9 KiB
Markdown
131 lines
4.9 KiB
Markdown
# 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 `$mYinVoCAtiOn` among other things. Coming from a Unix background and preferring some consistency I like to pretend it is case-sensitive so in this repo I'll strive for that but it's worth keeping in mind. Especially since **the Microsoft docs use case a lot** in variable and cmdlet names.
|
|
|
|
Variables use `$` 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. Use `[parameter(mandatory)]` to require one otherwise they are optional. 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
|
|
}
|
|
```
|
|
|
|
# foreach
|
|
|
|
Works on [arrays](https://learn.microsoft.com/en-us/powershell/scripting/lang-spec/chapter-09?view=powershell-7.3#92-array-creation), which can be concatenated with `+` and `+=` by the way.
|
|
|
|
```powershell
|
|
$letterArray = "a","b","c","d"
|
|
foreach ($letter in $letterArray)
|
|
{
|
|
Write-Host $letter
|
|
}
|
|
```
|
|
|
|
# items and paths
|
|
|
|
In PowerShell files and folders are called items. Some useful cmdlets for working with them are:
|
|
|
|
- [`New-Item`](https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.management/new-item?view=powershell-7.3#description) - create a file or folder
|
|
- [`Remove-Item`](https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.management/remove-item?view=powershell-7.3#description) - delete a file or folder
|
|
- [Move, Invoke, Rename etc...](https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.management/?view=powershell-7.3)
|
|
|
|
Here's how to loop through files in a folder using [`Get-ChildItem`](https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.management/get-childitem?view=powershell-7.3#description):
|
|
|
|
```powershell
|
|
foreach ($image Get-ChildItem .\images\* -Include *.png) {
|
|
Write-Host $image.BaseName
|
|
}
|
|
```
|
|
|
|
There are also a handful of useful functions for dealing with path strings by the names of [[Verb]-Path](https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.management/?view=powershell-7.3). Here are some examples:
|
|
|
|
```powershell
|
|
# Get parent folder
|
|
Split-Path -Parent $path
|
|
# Test if a file exists. For folder use `-PathType container`
|
|
Test-Path -Path $path -PathType leaf
|
|
```
|
|
|
|
# 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)
|