Functions

A function is a set of statements that are executed when the function name is called. Functions allow programmers to break down a problem into smaller chunks and help define a particular task. A couple of the major reasons for using functions are readability and reusability.

Function Definition

The syntax for defining functions in PowerShell is:

Function <Name>{
  <statement 1>
  <statement 2>
  <statement 3>
  ...
}

The Name of the function is used to invoke the function. Statements are written between the curly brackets { }.

Invoking a Function

To invoke or call a function, simply use the function’s name.

Function StatusDisplay{
  $date = get-date -format "MM/dd/yyyy HH:mm:ss"
  write-host "Script is running at $date"
}

StatusDisplay
# Output: Script is running at 02/27/2023 06:24:04

Parameters and Arguments

Parameters can be added to the function declaration to make them more flexible. The keyword param is used to declare all parameters in the first function statement.

Function <Name>{
  param (<parameter 1>, <parameter 2>, ...)
  <statements>
  ...
}

To invoke a function with arguments, the values passed to the function as parameters, list arguments after the function call:

<Name> <argument 1> <argument 2> ...

Example

Function StatusDisplay{
  param ($filename, $status)
  $date = get-date -format "MM/dd/yyyy HH:mm:ss"
  write-host "$filename is running $status at $date"
}

StatusDisplay "server.ps1" "normal"
# Output: server.ps1 is running normal at 02/27/2023 22:57:29

Default Parameters

A function will use default parameters unless arguments are explicitly provided in the function call. Default parameters are defined by assigning values to parameters:

Function <Name>{
  param (<parameter 1> = <value 1>, <parameter 2> = <value 2>, ...)
  <statements>
  ...
}

Example

Function StatusDisplay{
  param ($filename, $status = "normal")
  $date = get-date -format "MM/dd/yyyy HH:mm:ss"
  write-host "$filename is running $status at $date"
}

StatusDisplay "server.ps1"
# Output: server.ps1 is running normal at 02/27/2023 22:57:29

Importing Functions

Functions (as well as variables, cmdlets, and more) can be imported from another script .ps1 file using the Import-Module cmdlet. Its syntax is:

Import-Module <Path to file containing functions>

Example

Assume there’s a function called StatusDisplay in a script file called my_functions.ps1. All modules including the StatusDisplay function can be imported into another script like so:

Import-Module .\my_functions.ps1

StatusDisplay
# Output: Script is running at 02/28/2023 12:29:16