Windows PowerShell 1.0 Functions - Revision history

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2016-10-27T20:14:40Z
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<td width="20%">[[The Windows PowerShell 1.0 switch Statement|Previous]]<td align="center">[[Windows PowerShell 1.0 Essentials|Table of Contents]]<td width="20%" align="right">[[Working with File Systems in Windows PowerShell 1.0|Next]]</td>

<td width="20%">[[The Windows PowerShell 1.0 switch Statement|Previous]]<td align="center">[[Windows PowerShell 1.0 Essentials|Table of Contents]]<td width="20%" align="right">[[Working with File Systems in Windows PowerShell 1.0|Next]]</td>

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Neil: Text replacement - "" to "
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2016-05-05T14:43:53Z
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<td width="20%">[[The Windows PowerShell 1.0 switch Statement|Previous]]<td align="center">[[Windows PowerShell 1.0 Essentials|Table of Contents]]<td width="20%" align="right">[[Working with File Systems in Windows PowerShell 1.0|Next]]</td>

<td width="20%">[[The Windows PowerShell 1.0 switch Statement|Previous]]<td align="center">[[Windows PowerShell 1.0 Essentials|Table of Contents]]<td width="20%" align="right">[[Working with File Systems in Windows PowerShell 1.0|Next]]</td>

Neil: Text replacement - "BUY_WPS" to "powershell"

2016-02-01T21:12:13Z

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Neil at 14:45, 15 May 2009

2009-05-15T14:45:26Z

Neil at 13:48, 14 May 2009

2009-05-14T13:48:36Z

Neil: /* Passing Parameters to a Function */

2009-03-18T18:49:08Z

‎Passing Parameters to a Function

Neil: /* Windows PowerShell Function Administration */

2008-12-05T14:59:30Z

‎Windows PowerShell Function Administration

Neil: /* Windows PowerShell Function Administration */

2008-12-04T20:53:22Z

‎Windows PowerShell Function Administration

Neil: /* Using Functions in a Pipeline */

2008-12-04T20:51:54Z

‎Using Functions in a Pipeline

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 == Creating and Calling a Simple Windows PowerShell Function ==
-The most basic of Windows PowerShell functions are created using the ''function'' keyword followed by the name of the function. Finally, the list of statements to be executed are enclosed in curly braces. For example, the following function simply outputs a string before returning:
+The most basic of Windows PowerShell functions are created using the ''function'' keyword followed by the name of the function. Finally, the list of statements to be executed is enclosed in curly braces. For example, the following function simply outputs a string before returning:
 <pre>
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 == Passing Parameters to a Function ==
 <google>ADSDAQBOX_FLOW</google>
-In the preceding example, the function did not expect to be passed any parameters (also known as arguments). These are values which are entered on the command-line along with the function at the point that it is called. Windows PowerShell stores any parameters that were entered in a special variable called ''$args''. The ''$args'' variable is actually an array object with each parameter assigned to an array element (for more detailed information on working with arrays refer to the chapter entitled [[Working with Arrays in Windows PowerShell 1.0]]).
+In the preceding example, the function did not expect to be passed any parameters (also known as arguments). These are values that are entered on the command-line along with the function at the point that it is called. Windows PowerShell stores any parameters that were entered in a special variable called ''$args''. The ''$args'' variable is actually an array object with each parameter assigned to an array element (for more detailed information on working with arrays refer to the chapter entitled [[Working with Arrays in Windows PowerShell 1.0]]).
 In order to demonstrate the use of the ''$args'' variable in the context of Windows PowerShell functions, the following function displays the number of parameters passed into the function, and then multiplies the first two parameters:
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 == Specifying Named Parameters ==
-In the above example, we relied on the ''$args'' array to access any parameters which were passed through the function when it was called. Whilst this apprach works fine for simple functions, it can quickly become confusing as functions become more complex. An alternative mechanism is to declare the expected parameters and assign them variable names by which they may be accessed within the body of the function. This is achieved by placing the expected parameters in parentheses after the function name during the declaration. For example, the following function declares that two parameters are expected when the function is called, and names them "$firstname" and "$lastname" respectively.
+In the above example, we relied on the ''$args'' array to access any parameters that were passed through to the function when it was called. Whilst this approach works fine for simple functions, it can quickly become confusing as functions become more complex. An alternative mechanism is to declare the expected parameters and assign them variable names by which they may be accessed within the body of the function. This is achieved by placing the expected parameters in parentheses after the function name during the declaration. For example, the following function declares that two parameters are expected when the function is called, and names them "$firstname" and "$lastname" respectively.
 <pre>
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 </pre>
-Alternatively, the parameters may be specified using the names, which allows them to be passed in any order. In the following example, the last name parameter is specified before the first name. Because the parameter names are specified, however, the values are still assigned to the correct parameters:
+Alternatively, the parameters may be specified using the names, which allow them to be passed in any order. In the following example, the last name parameter is specified before the first name. Because the parameter names are specified, however, the values are still assigned to the correct parameters:
 <pre>
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 == Windows PowerShell Function Administration ==
-Functions declared within PowerShell are stored in the ''function'' namespace which is mapped to a virtual ''function:'' drive. As such, functions can be manipulated and administered much in the same way files in a filesytem are handled. It is possible, for example, to list the ''multiply_nnumbers'' function created earlier in this chapter using the ''dir'' command:
+Functions declared within PowerShell are stored in the ''function'' namespace which is mapped to a virtual ''function:'' drive. As such, functions can be manipulated and administered much in the same way files in a filesytem are handled. It is possible, for example, to list the ''multiply_numbers'' function created earlier in this chapter using the ''dir'' command:
 <pre>
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 As illustrated above, the function is now retained in the Windows PowerShell session. This technique applies equally to variables and any other settings that may be included in a script file which is subsequently ''dotted''.

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 == Passing Parameters to a Function ==
+<google>ADSDAQBOX_FLOW</google>
 In the preceding example, the function did not expect to be passed any parameters (also known as arguments). These are values which are entered on the command-line along with the function at the point that it is called. Windows PowerShell stores any parameters that were entered in a special variable called ''$args''. The ''$args'' variable is actually an array object with each parameter assigned to an array element (for more detailed information on working with arrays refer to the chapter entitled [[Working with Arrays in Windows PowerShell 1.0]]).

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	PS C:\Users\Administrator> rm function:/filelengths		PS C:\Users\Administrator> rm function:/filelengths
	</pre>		</pre>
		+
		+	== Loading Function Definitions from a Windows PowerShell Script File ==
		+
		+	Functions are not persistent across Windows PowerShell sessions. In other words, if you define a function from within the Windows PowerShell interactive shell environment and then exit the session, the function will no longer exist in future sessions. One way of quickly re-loading predefined functions is to place them into a script file and then load that script file from within the shell environment. The way this works isn't quite as most people might expect so this issue needs a little explanation. For the purposes of this description, we will create a simple function in a script file called ''myfunction.ps1'' as follows:
		+
		+	<pre>
		+	function hello ($name)
		+	{
		+	if ($name -ne "Fred")
		+	{
		+	return "Sorry $name, I was looking for Fred!"
		+	}
		+
		+	"Hello Fred!"
		+	}
		+	</pre>
		+
		+	Ordinarily, a script file is loaded and executed simply by referencing the name of the script at the PowerShell prompt. In fact, when this is performed, PowerShell executes the commands in the script and then discards any new settings, functions and variables once the script exists. So executing our ''myfunction.ps1'' script in the usual way isn't actually going to result in the new function being retained in the function namespace of the current session as illustrated below:
		+
		+	<pre>
		+	PS C:\Users\Administrator> dir function:hello
		+	Get-ChildItem : Cannot find path 'hello' because it does not exist.
		+	At line:1 char:4
		+	+ dir <<<< function:hello
		+	</pre>
		+
		+	In order to have the settings, functions and variables from a script file retained, it is necessary to perform a task known as ''dotting'' the script file (also known as ''sourcing'' in the UNIX and Linux worlds). This is achieved by prefixing the script name with a dot and a space as follows:
		+
		+	<pre>
		+	PS C:\Users\Administrator> . ./myfunction.ps1
		+	PS C:\Users\Administrator> dir function:hello
		+
		+	CommandType Name Definition
		+	----------- ---- ----------
		+	Function hello param($name) if ($name -ne "Fred")...
		+	</pre>
		+
		+	As illustrated above, the function is now retained in the Windows PowerShell session. This technique applies equally to variables and any other settings that may be included in a script file which is subsequently ''dotted''.

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 == Windows PowerShell Function Administration ==
-Functions declared within PowerShell are stored in the ''function'' namespace which is mapped to a virtual ''function:'' drive. As such, functions can be manipulated and administered much in the same way files in a filesytem are handled. It is possible, for example, to list the ''multiply'' function created earlier in this chapter using the ''dir'' command:
+Functions declared within PowerShell are stored in the ''function'' namespace which is mapped to a virtual ''function:'' drive. As such, functions can be manipulated and administered much in the same way files in a filesytem are handled. It is possible, for example, to list the ''multiply_nnumbers'' function created earlier in this chapter using the ''dir'' command:
 <pre>

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 <td width="20%">[[The Windows PowerShell 1.0 switch Statement|Previous]]<td align="center">[[Windows PowerShell 1.0 Essentials|Table of Contents]]<td width="20%" align="right">[[Working with File Systems in Windows PowerShell 1.0|Next]]</td>
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← Older revision		Revision as of 13:48, 14 May 2009
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		+	<td width="20%">[[The Windows PowerShell 1.0 switch Statement\|Previous]]<td align="center">[[Windows PowerShell 1.0 Essentials\|Table of Contents]]<td width="20%" align="right">[[Working with File Systems in Windows PowerShell 1.0\|Next]]</td>
		+	<tr>
		+	<td width="20%">The Windows PowerShell 1.0 switch Statement<td align="center"><td width="20%" align="right">Working with File Systems in Windows PowerShell 1.0</td>
		+	</table>
		+	<hr>
		+
		+
		+	<google>BUY_WPS</google>
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		+
	Windows PowerShell functions provide a way to organize scripts and promote re-use of code. They also provide a mechanism for creating custom cmdlets and filters. Windows PowerShell functions are easy to create and simple to use, as will be illustrated in the remainder of this chapter.		Windows PowerShell functions provide a way to organize scripts and promote re-use of code. They also provide a mechanism for creating custom cmdlets and filters. Windows PowerShell functions are easy to create and simple to use, as will be illustrated in the remainder of this chapter.

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 == Using Functions in a Pipeline ==
-As discussed in previous chapters, Windows PowerShell allows cmdlets to be executed in a sequence, with the results from one cmdlet used as input to the next cmdlet in the pipeline chain. Pipelines are created by separating the cmdlets by the pipe character (|). In order to include a function in a pipeline it is necessary for that function to process the $input variable. This variable contains the results from the previous cmdlet or function in the pipeline. In the following example, a function named ''filelengths'' is designed to take the output from the ''dir'' cmdlet'', iterate through the ''$input'' variable and display the name and length of each file:
+As discussed in previous chapters, Windows PowerShell allows cmdlets to be executed in a sequence, with the results from one cmdlet used as input to the next cmdlet in the pipeline chain. Pipelines are created by separating the cmdlets by the pipe character (|). In order to include a function in a pipeline it is necessary for that function to process the $input variable. This variable contains the results from the previous cmdlet or function in the pipeline. In the following example, a function named ''filelengths'' is designed to take the output from the ''dir'' cmdlet, iterate through the ''$input'' variable and display the name and length of each file:
 <pre>