There are two types of PowerShell Functions, basic and advanced. On the other hand, an advanced PowerShell function acts like cmdlets. A PowerShell function defines parameters, comment-based help information and statement blocks. This guide provides a step by step guide on how to write a PowerShell function. At the end of the guide you should be able to write your own PowerShell function. This section explains the meaning of each value in the syntax.
To make it easy to explain, I have added line numbers 1 to 20 to the syntax. You will learn step by step how to define the function block, add parameters and help files. This section 3m 9001v mask end with a brief explanation of the BeginProcess and End blocks.
This section covers the first stage in writing a Powershell Function: defining the function block. Now that you have added parameters and help to the Powershell function, it is time to add the actual scripts to the function. Before I begin, I will like to revisit the syntax of a Powershell function. A summarized version is shown below:. So far, we have added parameters and help information into the function. In this section I will discuss how to add statements to the 3 blocks of a PowerShell Function.
The Begin block is usually where you add scripts you require in the Process block. To work with the credential, I will use the Get-Credential cmdlet to extract the credential. But because this parameter is optional, I will add an IF statement as shown below. The Process block is where you add the main scripts for the function. In this instance, this block contains the Get-ADUser cmdlet.
Writing a PowerShell function may appear complex but it is actually easy. I hope this guide simplified it for you.So I thought it worth making a post to refer people to, rather than trying to respond in kind to each comment. There are a number of ways it can be done depending on your requirements and they are listed below.
The function is now available for use and if using the ISE will appear interactively when you start typing the name:. If the function is something that you wish to use regularly in your interactive PowerShell sessions then you can place the function in your PowerShell Profile and it will be available every time you open your PowerShell console.
If you are unsure what a PowerShell profile is or how to use one, there is some good info here. A quick way to create one is:. Once you have created a PowerShell profile, place the function in the profile and save and close.
Now every time you open your PowerShell console the function will be available. If you wish to use the function in a script, place the function in the script above the sections where you need to use it. Typically this will be towards the top.
The plus side of doing it this way is everything is contained in one file, a negative is that if you have a number of functions then readability of the script is reduced since there may be a long way to scroll down before anything of significance starts to happen. Using a PowerShell module is a more advanced and significantly more structured and powerful method of achieving what was done in 4.
Essentially they are a method to package up your reusable functions and make them available in a manner similar to how other teams in Microsoft and third-parties produce suites of PowerShell cmdlets for consumption.
However, it would be a good practice to add the Import-Module line to your script, so that another user is aware of where you are getting the functionality from. You can add parameters to a script, pretty much the same as you would do to a function. Functions script file Tools. Thanks this is the best explanation i have found of functions.This avoids redundant script blocks and facilitates code maintenance.
In contrast to most compiled languages, such as C, the use of functions is not required in PowerShell. It is worth pointing out that, even though PowerShell is an object-oriented language, functions are defined as in procedural languages and not as methods in classes.
In PowerShell, as in other programming languages, functions define the scope of variables. The values of variables defined within a function block are not available outside the function. However, to avoid undesirable side effects, you should not use the same name for local and global variables. Scopes also affect the functions themselves. By default, functions that you define in a script are not available at the PowerShell prompt. You can change this by using the scope identifier, as in the example below:.
With this command, you are extending the scope of the function Get-UserInput to globalwhich makes the function available outside the script where you defined it. If you define a function at the PowerShell prompt to save typing of complex commands, the function only exists during this session. To make it available in future sessions, you have to add it to your PowerShell profile. In an interactive session, you will probably only use simple functions with just one statement; however, functions can get quite complex in scripts.
The definition begins with the keyword function ; a declaration of the return value is not provided. As mentioned above, you can prepend the name of the function with a value for the scope.
The naming should follow the PowerShell convention in the form verb-nounas with all integrated PowerShell cmdlets Get-Processfor instance. PowerShell offers many more features here than other languages do, but this also means a steeper learning curve. It is already unusual that two different ways exist to define parameters.
As in most languages, you can define the list of parameters directly after the function name. Alternatively, you can define the parameters at the beginning of the function block with the keyword param. It is a matter of taste which option you prefer. However, if you intend to use several of the numerous attributes and work with predefined values, you should use the param block to improve the readability of your script.
Hence, you should follow this convention for your functions. In the declaration, you define the name of a parameter as a variable, which allows you to access its value in the function.
This example packs the command to run a Windows 8. For instance, if you want to launch the Notepad app, you could call the function in the following way:. In the above example, the sole parameter is defined without the use of additional attributes.
However, by assigning a data type, you could ensure that the function accepts only a value of the type String. In most cases, you will want to intercept the function call if no parameter has been passed.A function is a list of PowerShell statements that has a name that you assign. When you run a function, you type the function name. The statements in the list run as if you had typed them at the command prompt. Like cmdlets, functions can have parameters.
The parameters can be named, positional, switch, or dynamic parameters. Function parameters can be read from the command line or from the pipeline. Functions can return values that can be displayed, assigned to variables, or passed to other functions or cmdlets. You can also specify a return value using the return keyword. The return keyword does not affect or suppress other output returned from your function.
However, the return keyword exits the function at that line. The function's statement list can contain different types of statement lists with the keywords BeginProcessand End.
These statement lists handle input from the pipeline differently. Functions can also act like cmdlets.
You can create a function that works just like a cmdlet without using C programming. Functions do not have to be complicated to be useful. The simplest functions have the following format:. To add statements to the function, type each statement on a separate line, or use a semi-colon ; to separate the statements.
How-to: PowerShell Functions and Filters
For example, the following function finds all. You can create a toolbox of useful small functions. You can assign any name to a function, but functions that you share with others should follow the naming rules that have been established for all PowerShell commands. Functions names should consist of a verb-noun pair in which the verb identifies the action that the function performs and the noun identifies the item on which the cmdlet performs its action.
Functions should use the standard verbs that have been approved for all PowerShell commands. These verbs help us to keep our command names simple, consistent, and easy for users to understand. You can use parameters with functions, including named parameters, positional parameters, switch parameters, and dynamic parameters. You can define any number of named parameters.You can add parameters to the advanced functions that you write, and use parameter attributes and arguments to limit the parameter values that function users submit with the parameter.
The parameters that you add to your function are available to users in addition to the common parameters that PowerShell adds automatically to all cmdlets and advanced functions. Beginning in PowerShell 3. Splatting is valid on simple and advanced functions. When you supply strings as arguments to parameters that expect a different type, PowerShell implicitly converts the strings to the parameter target type.
Advanced functions perform culture-invariant parsing of parameter values. By contrast, a culture-sensitive conversion is performed during parameter binding for compiled cmdlets.
In this example, we create a cmdlet and a script function that take a [datetime] parameter. The current culture is changed to use German settings.
A German-formatted date is passed to the parameter. Static parameters are parameters that are always available in the function. Most parameters in PowerShell cmdlets and scripts are static parameters. The following example shows the declaration of a ComputerName parameter that has the following characteristics:. All attributes are optional. However, if you omit the CmdletBinding attribute, then to be recognized as an advanced function, the function must include the Parameter attribute.
You can add one or multiple attributes in each parameter declaration. There's no limit to the number of attributes that you can add to a parameter declaration. The Parameter attribute is used to declare the attributes of function parameters. The Parameter attribute is optional, and you can omit it if none of the parameters of your functions need attributes. But, to be recognized as an advanced function, rather than a simple function, a function must have either the CmdletBinding attribute or the Parameter attribute, or both.
The Parameter attribute has arguments that define the characteristics of the parameter, such as whether the parameter is mandatory or optional. Use the following syntax to declare the Parameter attribute, an argument, and an argument value.
The parentheses that enclose the argument and its value must follow Parameter with no intervening space. Use commas to separate arguments within the parentheses. Use the following syntax to declare two arguments of the Parameter attribute.
If you use the Parameter attribute without arguments, as an alternative to using the CmdletBinding attribute, the parentheses that follow the attribute name are still required. The Mandatory argument indicates that the parameter is required. If this argument isn't specified, the parameter is optional. The following example declares the ComputerName parameter.
It uses the Mandatory argument to make the parameter mandatory. The Position argument determines whether the parameter name is required when the parameter is used in a command.
When a parameter declaration includes the Position argument, the parameter name can be omitted and PowerShell identifies the unnamed parameter value by its position, or order, in the list of unnamed parameter values in the command.Are they a tool to be used occasionally for recurring blocks of code? Alternatively, will functions become the central methodology for every script we create?
To elaborate on what I mean, let us consider three statements from people with different scripting knowledge:. Instead, Guy has invented a basic function to calculate batting averages.
I realise that my hybrid example may please neither cricket lovers nor baseball aficionados. By using keyboard input, we are going to take two numbers and divide the first number by the second, and thus calculate the average in traditional math fashion.
Before we get down to using my Get-BatAvg Function, here are a few considerations. What you place inside the script block is the same code that you could execute normally outside the scope of the function. The whole point is that you can execute this block of PowerShell code simply by typing the name of the function.
Here is a classic example for dissecting, fiddling, changing stuff to see what happens, and thus truly learning how functions are constructed.
I re-jigged the first script to make it more suitable for baseball. Incidentally, square brackets mean optional information.
Default order -Name -Hits -AtBats. This utility will also guide you through troubleshooting; the dashboard will indicate whether the root cause is a broken link, faulty equipment or resource overload. What I like best is the way NPM suggests solutions to network problems.
Its also has the ability to monitor the health of individual VMware virtual machines.
If you are interested in troubleshooting, and creating network maps, then I recommend that you try NPM on a day free trial. From a learning point of view, I wanted to show how there are numerous styles for creating Windows PowerShell functions. I prefer example 1 above. You need to supply three parameters, a name, the number of runs, and the number of dismissals. Thankfully the utilities are displayed logically: monitoring, network discovery, diagnostic, and Cisco tools.
Here is a completely different function example, which is nothing to do with batting averages. In this case we need a specialist function that displays the primary key for a particular WMI Class. Secondly, you can introduce parameters which modify the code, for example, to change a name or a numeric value within the code block.A place to learn about PowerShell and share stories of automation.
I know I can change them in the web portal, but is there a faster way of doing it through Windows PowerShell? There absolutely is!
PowerShell Basics: How to Create a Function
Q: Hey, Scripting Guy! Does that mean I can use PowerShell to consume them? Could you show me how to authenticate t. I can see there is this cool cmdlet called Invoke-RestMethod.
Could you give me a hand getting started? Just like I mentioned in my first post, PowerShell supports a lot of stuff that makes it pretty easy to dive in and get stuff running. The following two examples are supported in PowerShell, but not something you should really be doing for any reusable tool set. Putting your parameters arguments next to the function name in parenthesis.
NET Core. Recordset ADOR. Paste your code snippet. Cancel Ok.Chapter 21 - Advanced jwl.truckmountsprioritizing.pw4