From 06cbe3694a488650375a84a3eb0d56d65236169a Mon Sep 17 00:00:00 2001
From: Michele Cereda <cereda.michele@gmail.com>
Date: Thu, 15 Sep 2022 18:01:10 +0200
Subject: [PATCH] Greatly improved TL;DR, added ToC

---
 knowledge base/powershell.md | 82 +++++++++++++++++++++++++++++++++---
 1 file changed, 76 insertions(+), 6 deletions(-)

diff --git a/knowledge base/powershell.md b/knowledge base/powershell.md
index 72031ab..20f3a53 100644
--- a/knowledge base/powershell.md	
+++ b/knowledge base/powershell.md	
@@ -1,22 +1,92 @@
-# Windows PowerShell
+# Windows PowerShell <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+2. [Further readings](#further-readings)
+3. [Sources](#sources)
 
 ## TL;DR
 
 ```powershell
-# print the value of the PATH environment variable
-Write-Output $env:PATH
-
-# calculate the hash of a file
+# Calculate the hash of a file.
 CertUtil -hashfile path/to/file sha256
 
-# get super user privileges
+# Get super user privileges.
 powershell Start-Process powershell -Verb runAs
+
+# Assign values to variables.
+$variableName = 'value'
+$response = Invoke-WebRequest -Uri 'https://jsonplaceholder.typicode.com/users'
+
+# Print the value of the PATH environment variable.
+$env:PATH
+Write-Output $env:PATH
+Write-Host $env:PATH
+
+# Pipe the output of a command into another.
+$users = $response | ConvertFrom-Json
+$response | ConvertFrom-Json | Select-Object -Property username,email
+
+# Access Objects' properties via dot-notation.
+$users.id
+(Invoke-WebRequest -Uri 'https://jsonplaceholder.typicode.com/users').Content
+
+# Show selected Objects' properties.
+$users | Select-Object -Property id,username,email
+$users | select -Property id,username,email
+
+# Show selected Objects' properties (expanded).
+# Dot-notation automatically expands the output.
+$users | Select-Object -Expand id,username,email
+$users | select -Expand id,username,email
+
+# Filter Objects' values.
+$users | Where-Object -Property id -EQ 10
+$users | where {$_.id -eq 10}
+$users | where {($_.id -eq 10) -or ($_.id -lt 3)}
+
+# Split a command on multiple lines.
+Invoke-WebRequest `
+  -Uri 'https://jsonplaceholder.typicode.com/users' `
+  -UseBasicParsing `
+| select -Expand Content `
+| ConvertFrom-Json `
+| Select-Object -Property id,username,email
+
+# Filter out nodes name and their issues from K8S nodes' command output.
+# Both contructions do the same operations and have the same output.
+kubectl get nodes -o json `
+| ConvertFrom-Json `
+| Select-Object -ExpandProperty items `
+| Select-Object -Property `
+    @{l="Node";e={$_.metadata.name}},`
+    @{l="Issues";e={$_.status.conditions `
+      | Where-Object { ($_.status -ne "False") -and ($_.type -ne "Ready") } `
+      | Select-Object -ExpandProperty type}}
+(kubectl get nodes -o json | ConvertFrom-Json).items `
+| select @{l="Node";e={$_.metadata.name}},@{l="Issues";e={`
+    ($_.status.conditions | where {($_.status -ne "False") -and ($_.type -ne "Ready")}).type`
+  }}
 ```
 
 ## Further readings
 
 - [How to print environment variables to the console in PowerShell?]
 - [Running PowerShell as Administrator with the Command Line]
+- [Multiline Command]
+
+## Sources
+
+- [Working with JSON data in PowerShell]
+- [JSON file to table]
+- [Retrieve JSON object by field value]
+- [Select-Object of multiple properties]
+- [Multiple -and -or in PowerShell Where-Object statement]
 
 [how to print environment variables to the console in powershell?]: https://stackoverflow.com/questions/50861082/how-to-print-environment-variables-to-the-console-in-powershell#50861113
+[json file to table]: https://stackoverflow.com/questions/31415158/powershell-json-file-to-table#31415897
+[multiline commands]: https://shellgeek.com/powershell-multiline-command/
+[multiple -and -or in powershell where-object statement]: https://stackoverflow.com/questions/24682939/multiple-and-or-in-powershell-where-object-statement#24683254
+[retrieve json object by field value]: https://stackoverflow.com/questions/16575419/powershell-retrieve-json-object-by-field-value#16580887
 [running powershell as administrator with the command line]: https://adamtheautomator.com/powershell-run-as-administrator/
+[select-object of multiple properties]: https://stackoverflow.com/questions/44142738/select-object-of-multiple-properties#44142777
+[working with json data in powershell]: https://devblogs.microsoft.com/scripting/working-with-json-data-in-powershell/