Essential Books

null

suggest change

$null is used to represent absent or undefined value.

$null can be used as an empty placeholder for empty value in arrays: 

PS C:\> $array = 1, "string", $null
PS C:\> $array.Count
3

When we use the same array as the source for ForEach-Object, it will process all three items (including $null): 

PS C:\> $array | ForEach-Object {"Hello"}
Hello
Hello
Hello

Be careful! This means that ForEach-Object WILL process even $null all by itself: 

PS C:\> $null | ForEach-Object {"Hello"} # THIS WILL DO ONE ITERATION !!!
Hello

Which is very unexpected result if you compare it to classic foreach loop: 

PS C:\> foreach($i in $null) {"Hello"} # THIS WILL DO NO ITERATION
PS C:\>
Found a mistake? Have a question or improvement idea? Let me know.

Feedback about page:

Feedback:
Optional: your email if you want me to get back to you:

Automatic variables:
* Automatic Variables
* OFS
*
* null
* error
* pid
* Boolean values
* PSItem
Table Of Contents
0 Getting started
1 Loops
2 Operators
3 Using ShouldProcess
4 PowerShell classes
5 Switch statement
6 Working with objects
7 Using existing static classes
8 Basic set operations
9 PowerShell functions
10 Sending email
11 Handling secrets and credentials
12 PowerShell Remoting
13 PowerShell Streams, debug, verbose, warning, error output
14 Variables in PowerShell
15 Communicating with RESTful APIs
16 Working with the PowerShell pipeline
17 PowerShell Background Jobs
18 Return behavior in PowerShell
19 XML
20 Introduction to psake
21 Progress bar
22 Strings
23 TCP communication
24 SharePoint module
25 Aliases
26 Automatic variables
27 Environment variables
28 PowerShell profiles
29 Enforcing script pre-requisites
30 Using the help system
31 Splatting
32 Desired state configuration
33 Signing scripts
34 Security and cryptography
35 CSV parsing
36 Introduction to Pester
37 Modules scripts and functions
38 PowerShell.exe command-line
39 Common parameters
40 Parameter sets
41 Regular Expressions
42 PowerShell dynamic parameters
43 WMI and CIM
44 GUI in PowerShell
45 Conditional logic
46 URL encode/decode
47 MongoDB
48 Running executables
49 Error handling
50 HashTables
51 ActiveDirectory module
52 SQL queries
53 Automatic variables #2
54 Package management
55 Cmdlet naming
56 Built-in variables
57 Creating DSC class-based resources
58 PowerShell modules
59 PowerShell workflows
60 How to downloaded latest artifact from artifactory
61 Calculated properties
62 Special operators
63 Anonymize IP v4 and v6
64 Comment-based help
65 AWS S3
66 AWS Rekognition
67 PSScriptAnalyzer
68 Naming conventions
69 Embedding managed code (C#, VB)
70 Archive module
71 Infrastructure automation
72 Scheduled tasks module
73 ISE module
74 Recipies
75 Contributors