| Service | Microsoft Docs article | Related commit history on GitHub | Change details |
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| learn | Everything About Switch | https://github.com/MicrosoftDocs/PowerShell-Docs/commits/staging/reference/docs-conceptual/learn/deep-dives/everything-about-switch.md | --- description: The switch statement in PowerShell offers features that aren't found in other languages. Previously updated : 10/05/2021 Last updated : 01/28/2022 Title: Everything you ever wanted to know about the switch statement --- # Everything you ever wanted to know about the switch statement Like many other languages, PowerShell has commands for controlling the flow of execution within your -scripts. One of those statements is the [switch][switch] statement and in PowerShell, it offers features -that aren't found in other languages. Today, we take a deep dive into working with the PowerShell -`switch`. +scripts. One of those statements is the [switch][switch] statement and in PowerShell, it offers +features that aren't found in other languages. Today, we take a deep dive into working with the +PowerShell `switch`. > [!NOTE]-> The [original version][original version] of this article appeared on the blog written by [@KevinMarquette][@KevinMarquette]. The -> PowerShell team thanks Kevin for sharing this content with us. Please check out his blog at -> [PowerShellExplained.com][PowerShellExplained.com]. +> The [original version][original version] of this article appeared on the blog written by +> [@KevinMarquette][@KevinMarquette]. The PowerShell team thanks Kevin for sharing this content with +> us. Please check out his blog at [PowerShellExplained.com][PowerShellExplained.com]. ## The `if` statement switch -Regex ( $message ) } ``` -I have more examples of using regex in another article I wrote: [The many ways to use regex][The many ways to use regex]. +I have more examples of using regex in another article I wrote: +[The many ways to use regex][The many ways to use regex]. ### -File write-error -message $PSItem : Error: out of disk space In this case, if we hit any lines that start with `Error` then we get an error and the switch stops. This is what that `break` statement is doing for us. If we find `Error` inside the string and not-just at the beginning, we write it as a warning. We do the same thing for `Warning`. It's -possible that a line could have both the word `Error` and `Warning`, but we only need one to -process. This is what the `continue` statement is doing for us. +just at the beginning, we write it as a warning. We do the same thing for `Warning`. It's possible +that a line could have both the word `Error` and `Warning`, but we only need one to process. This is +what the `continue` statement is doing for us. ### Break labels It still executes the same way and gives a better visual break when quickly look We need to revisit regex to touch on something that isn't immediately obvious. The use of regex populates the `$matches` variable. I do go into the use of `$matches` more when I talk about-[The many ways to use regex][The many ways to use regex]. Here is a quick sample to show it in action with named matches. +[The many ways to use regex][The many ways to use regex]. Here is a quick sample to show it in +action with named matches. ``` powershell $message = 'my ssn is 123-23-3456 and credit card: 1234-5678-1234-5678' WARNING: message may contain a credit card number: 1234-5678-1234-5678 You can match a `$null` value that doesn't have to be the default. -``` powershell -$value = $null --switch ( $value ) +```powershell +$values = '', 5, $null +switch ( $values ) {- $null - { - 'Value is null' - } - default - { - 'value is not null' - } + $null { "Value '$_' is `$null or an empty string" } + '' { "Value '$_' is an empty string" } + default { "Value [$_] is not an empty string or `$null" } }+``` ++Notice that the empty string value doesn't match `$null` but `$null` matches both `$null` and an +empty string. ```Output-Value is null +Value '' is an empty string +Value [5] is not an empty string or $null +Value '' is $null or an empty string +Value '' is an empty string ``` -Same goes for an empty string. +Also, be careful with empty returns from cmdlets. Cmdlets or pipelines that have no output are +treated as an empty array that does not match anything, including the `default` case. -``` powershell -switch ( '' ) +```powershell +$file = Get-ChildItem NonExistantFile* +switch ( $file ) {- '' - { - 'Value is empty' - } - default - { - 'value is a empty string' - } + $null { '$file is $null' } + default { "`$file is type $($file.GetType().Name)" } }--```Output -Value is empty +# No matches ``` ### Constant expression Do-Action Enabled-AdminMenu ``` -This is a clean way to evaluate and take action on the status of several boolean fields. The -cool thing about this is that you can have one match flip the status of a value that hasn't been +This is a clean way to evaluate and take action on the status of several boolean fields. The cool +thing about this is that you can have one match flip the status of a value that hasn't been evaluated yet. ``` powershell Do-Action Show-Animation ``` -Setting `$isEnabled` to `$true` in this example makes sure that `$isVisible` is also set to -`$true`. Then when `$isVisible` gets evaluated, its scriptblock is invoked. This is a bit -counter-intuitive but is a clever use of the mechanics. +Setting `$isEnabled` to `$true` in this example makes sure that `$isVisible` is also set to `$true`. +Then when `$isVisible` gets evaluated, its scriptblock is invoked. This is a bit counter-intuitive +but is a clever use of the mechanics. ### $switch automatic variable access that value directly. I would call it madness. ### Hashtables -One of my most popular posts is the one I did on [hashtables][hashtables]. One of the use cases for a -`hashtable` is to be a lookup table. That is an alternate approach to a common pattern that a +One of my most popular posts is the one I did on [hashtables][hashtables]. One of the use cases for +a `hashtable` is to be a lookup table. That is an alternate approach to a common pattern that a `switch` statement is often addressing. ``` powershell |