A variable is a named place to store a value or collection of objects for later use. In PowerShell, use the dollar sign to access the contents; it is not part of the variable name. Variables can hold computer names, services, processes, XML documents, or other objects. section 16.0 section 16.1
Store and reuse a value
Assign a value with the equals sign, then use the variable wherever the value belongs: $var = "SRV-02" $var A variable can replace a literal command argument: $var = "13481" Get-Process -Id $var PowerShell does not require a separate declaration before first use, and variables normally disappear when the shell session closes. section 16.2 section 16.1
Use these naming and assignment habits:
- Choose meaningful, succinct names such as $computername; avoid spaces even though ${My Variable} is supported. section 16.2 section 16.8
- Assign a comma-separated list to store multiple objects: $computers = 'SRV-02','SERVER1','localhost'. section 16.4
- Read collection elements with indexes beginning at 0; use -1 for the last element and Count to see the number of objects. section 16.4.1
- Assign a new value to replace the entire variable or an indexed element; methods such as ToLower() return new strings rather than changing the original. section 16.4.1 section 16.4.2
PS > $computername = 'SRV-02' PS > $phrase = "The computer name is $computername" PS > $phrase The computer name is SRV-02
Use double quotation marks when a string should substitute a variable's current contents during parsing. section 16.3
Single-quoted strings treat variable text literally. Double-quoted strings substitute embedded variables when the string is first parsed, so changing the original variable later does not update the already-created string. Escape a dollar sign with the backtick when you want the variable name displayed, and use `n for a newline. section 16.3
Control the stored type
Input from Read-Host arrives as a string. Multiplying the string "100" by 10 repeats its text instead of performing numeric multiplication. Declare an integer when assigning the input: [int]$number = Read-Host "Enter a number" $number = $number * 10 Entering 100 produces 1000. Entering nonnumeric text raises a conversion error. Type declarations can therefore prevent later logic errors when a variable is expected to contain one kind of object. section 16.6 section 16.8
Process collections with indexing, pipelines, or ForEach-Object. For example, pipe $computers to ForEach-Object and assign the resulting lowercase strings back to $computers; use Select-Object to select a property such as Length. Variables also make commands easier to parameterize: store a computer name or path, then substitute it into a repeatable script. section 16.4.3 section 19.3
PowerShell provides New-Variable, Set-Variable, Remove-Variable, Get-Variable, and Clear-Variable, but ordinary assignment usually handles creation, reading, and updating more simply. Scope controls where variables exist: the global scope contains script scopes, while functions have private scopes; a scope disappears when its execution ends. section 16.7 section 19.7
Administrator workflow
Store command results for inspection or export. A background job can retrieve processes from two computers, receive its results into a variable, display them, and export them to CLIXML. A service query can be stored, narrowed to bits and the print spooler service, displayed, and exported to CSV. section 16.10
