The Basics of the Windows PowerShell 1.0 Interactive Shell

Windows PowerShell is both a scripting language and an interactive shell. In interactive shell mode, PowerShell provides a command line prompt at which commands may be entered and executed interactively. The purpose of this chapter is to cover the basics of using the PowerShell 1.0 interactive shell.

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The Windows PowerShell Command Prompt

The PowerShell interactive prompt may be accessed in two ways. One option is to launch PowerShell from the Start menu by selecting Start -> All Programs -> Windows PowerShell 1.0 -> Windows PowerShell. Alternatively, PowerShell may be launched from the Windows Command Prompt (cmd.exe) window simply by entering the command powershell. Once loaded, PowerShell will display copyright information, followed by the shell prompt:

Windows PowerShell
Copyright (C) 2006 Microsoft Corporation. All rights reserved.

PS C:\Users\Administrator>

The interactive shell prompt consists of the letter PS to indicate that the user is working within the PowerShell, followed by the current working directory. The prompt is terminated with a '>' character after which the cursor appears awaiting user input. The current working directory indicates that any file system based operations will take place relative to that directory on the file system. Typing the dir or ls command, therefore, will provide a listing of files and sub-directories in the current working directory (C:\Users\Administrator) in this case:

PS C:\Users\Administrator> dir


    Directory: Microsoft.PowerShell.Core\FileSystem::C:\Users\Administrator


Mode                LastWriteTime     Length Name
----                -------------     ------ ----
d-r--         11/7/2008   4:26 PM            Contacts
d-r--         11/7/2008   4:26 PM            Desktop
d-r--         11/7/2008   4:26 PM            Documents
d-r--         11/7/2008   4:26 PM            Downloads
d-r--         11/7/2008   4:26 PM            Favorites
d-r--         11/7/2008   4:26 PM            Links
d-r--         11/7/2008   4:26 PM            Music
d-r--         11/7/2008   4:26 PM            Pictures
d-r--         11/7/2008   4:26 PM            Saved Games
d-r--         11/7/2008   4:26 PM            Searches
d-r--         11/7/2008   4:26 PM            Videos

By default, this will be the home directory of the user who invoked PowerShell. The directory may be changed using cd command, for example:

PS C:\Users\Administrator> cd \windows
PS C:\Windows>

PowerShell Command Line Editing Keys

PowerShell provides a number of special key sequences which speed the task of creating and editing commands in the interactive shell, each of which is outlined in the following table:

Key Sequence	Description
Left Arrow	Moves the command line cursor one character to the left.
Right Arrow	Moves the command line cursor one character to the right.
Ctrl+Left Arrow	Moves the command line cursor one word to the left.
Ctrl+Right Arrow	Moves the command line cursor one word to the right.
Delete	Deletes the character in the command line at the current cursor position.
Backspace	Deletes the character immediately to the right of the current cursor position.
Insert	Toggles between character insert and overwrite modes.
Home	Relocates the cursor to the beginning of the command line.
End	Relocates the cursor to the end of the command line.
Tab	Performs command completion operation whereby the shell attempts to guess at the remainder of the command being entered.
F7	Displays a new window containing the command history from which previous commands may be selected.

PowerShell Command Completion

After a few characters of a command, parameter, file name, variable or variable property have been entered at the PowerShell command line prompt, the Tab key may be pressed to instruct PowerShell to complete the remainder of the entry. For example, if the first few characters of a command have been entered, PowerShell will try to find the best match for a command and fill in the remainder of the command name. If the command selected by PowerShell is not the correct one, pressing the Tab key repeatedly will cycle through all the possible matches until the correct one is displayed. Similarly, if a partial file name is entered followed by the Tab key, PowerShell will populate the command line with file name from the current directory. If, once again, the first match displayed by PowerShell is not the desired file, the Tab key can be pressed repeatedly until the correct match is displayed.

Tab completion is particularly useful for finding the properties and methods of a variable. As an example, suppose a variable named $mynumber is assigned a numerical value and we want to find out what the type of that value is. We assume there must be a method we can call on on the varaible to get the type but do not know what that method is called. To cycle through the available methods we simply enter the name of the variable, followed by a . character and then the first few characters of the method (we are assuming it will begin with Get), We then press the Tab key until we find the method that does what we need, in this case, GetType():

PS C:\Users\Administrator> $mynum.GetType(

We then enter the closing parentheses ) since we do not need to pass any arguments through to the method, and then press enter to execute the command:

PS C:\Users\Administrator> $mynum.GetType()

IsPublic IsSerial Name                                     BaseType
-------- -------- ----                                     --------
True     True     Double                                   System.ValueType