Microsoft WSH and VBScript Programming for the Absolute Beginner Part 10 ppsx

70 Unfortunately, the statement’s syntax requirements have not been followed. The MsgBox() function requires that all text messages be enclosed within a pair of quotation marks. If you look closely, you will see that the closing quotation mark is omitted. Figure 3.7 shows the error produced by this statement at run-time. Reserved Characters Like any programming language, VBScript has a collection of reserved words. Reserved words are words that you cannot use within your scripts because VBScript also assigns a special meaning to them. Some of these words are reserved because they are part of the language itself, and others are reserved for future use. Table 3.2 lists VBScript’s reserved words. The important thing to remember when it comes to VBScript reserved words is that you can only use them as intended (that is, you cannot use them as variables, constants, and procedure names). Adding Comments One of the easiest VBScript statements to understand is the comment statement. The com- ment statement gives you the ability to add to your VBScripts descriptive text that docu- ments why you wrote the script the way you did. Documenting your scripts with comments makes them easier to support and helps others who may come after you to pick up where you left off. Comments do not have any affect on the execution of your scripts and you should use them liberally. Comments can be added to scripts using the VBScript Rem (short for remark) statement, as follows: Rem Use the VBScript MsgBox() function to display a message MsgBox “Thanks for playing!” Comments also can be created using the ‘ character: ‘ Use the VBScript MsgBox() function to display a message MsgBox “Thanks for playing!” Microsoft WSH and VBScript Programming for the Absolute Beginner, Second Edition Figure 3.7 The error message caused by an unmatched quotation mark in a MsgBox() statement. 71 Chapter 3 • VBScript Basics And EndIf LSet RSet As Enum Me Select Boolean Eqv Mod Set ByRef Event New Shared Byte Exit Next Single ByVal False Not Static Call For Nothing Stop Case Function Null Sub Class Get On Then Const GoTo Option To Currency If Optional True Debug Imp Or Type Dim Implements ParamArray TypeOf Do In Preserve Until Double Integer Private Variant Each Is Public Wend Else Let RaiseEvent While ElseIf Like ReDim With Empty Long Rem Xor End Loop Resume TABLE 3.2 VBSCRIPT’ S C OLLECTION OF R ESERVED W ORDS The ‘ character is my preferred style. I find it less visually intrusive and just as effective. Also, you can add a comment to the end of any statement: MsgBox “Thank you for playing” ‘Display a thank you message One sign of an experienced programmer is the amount of and usefulness of comments added to his or her scripts. Consider adding comments that describe the function of variables, constants, and arrays; also use them to explain com- plicated pieces of coding. HINT 72 Comments also can be used to create a script template, which will provide additional struc- ture to your VBScripts. For example, consider the following template: ‘************************************************************************* ‘Script Name: ScriptName.vbs ‘Author: Author Name ‘Created: MM/DD/YY ‘Description: Xxxxxxxxxxxxxxxxxxxxxxxxx. ‘************************************************************************* ‘Initialization Section Option Explicit On Error Resume Next Dim… Const… Set… ‘Main Processing Section ‘Procedure Section ‘This function Function Xxxxx(Zzzz) Xxxxxxxxxx End Function This template begins with a documentation section that provides a place to record the script’s name, its author, its creation date, and a brief description. Other information that you might want to add here includes • Instructions for running the script • Documentation for any arguments the script expects to receive at execution time • Documentation of the recent updates to the script, including when, by whom, and why • Copyright information • Contact or support information Microsoft WSH and VBScript Programming for the Absolute Beginner, Second Edition The rest of the template is divided into three sections. • Initialization Section. Contains statements that globally affect the scripts, including Option Explicit and On Error, as well as the declaration of any variables, constants, arrays, and objects used by the script. • Main Processing Section. This section contains the statements that control the main processing logic of the script. The statements in this section access the resources defined in the Initialization Section as necessary, and call on the procedures and functions located in the Procedure Section. • Procedure Section. This section contains all the script’s procedures. Procedures are groups of statements that can be called and executed as a unit. You’ll learn how to work with procedures in Chapter 7, “Using Procedures to Organize Scripts.” Mastering the VBScript Object Model In Chapter 2, “Overview of the Windows Script Host,” you learned about the WSH core object model and its properties and methods. You also learned how to instantiate WSH objects to access and manipulate their properties and methods. VBScript also provides two collections of objects that you can use in your scripts. Table 3.3 provides an overview of VBScript’s built-in or core objects. Check out Chapter 11 “Working with Built-in VBScript Objects” to learn more about VBScript’s built-in objects. 73 Chapter 3 • VBScript Basics Object Name Description Class Provides scripts with access to class events Err Provides scripts with access to information about run-time errors Match Provides scripts with access to the read-only properties of a regular expression match Matches Collection A collection of regular expression Match objects RegExp Supports regular expressions SubMatches Collection Provides scripts with access to read-only values of regular expression submatch strings TABLE 3.3 VBSCRIPT BUILT- IN O BJECTS 74 Working with VBScript Run-Time Objects In addition to its core object model, VBScript’s FileSystemObject object also provides a number of run-time objects. As Table 3.4 shows, your scripts can use these objects and their proper- ties and methods to interface with the Windows file system. The WSH core object model provides access to a number of Windows resources. Absent from this model is a file system object. Therefore, to access system files from your VBScripts, you’ll need to learn how to work with VBScript’s FileSystemObject object. With this object, your scripts will be able to • Check for the existence of files and folders before attempting to work with them • Create and delete files and folders • Open and read files • Write or append to files • Close files • Copy and move files and folders Microsoft WSH and VBScript Programming for the Absolute Beginner, Second Edition Object Name Description Dictionary Stores data key, item pairs. Properties: Count, Item, Key. Methods: Add, Exists, Items, Keys, Remove, RemoveAll. Drive Provides script with access to disk properties. Properties: AvailableSpace, DriveLetter, DriveType, FileSystem, FreeSpace, IsReady, Path, RootFolder, SerialNumber, ShareName, TotalSize, VolumeName. Methods: This object does not support any methods. Drives Collection Provides script with access to information regarding a drive’s location. Properties: Count, Item. Methods: This object does not support any methods. File Provides script with access to file properties. Properties: Attributes, DateCreated, DateLastAccessed, DateLastModified, Drive, Name, ParentFolder, Path, ShortName, ShortPath, Size, Type. Methods: Copy, Delete, Move, OpenAsTextStream. TABLE 3.4 VBSCRIPT RUN-TIME O BJECTS 75 Chapter 3 • VBScript Basics Object Name Description Files Collection Provides scripts with access to files stored in a specified folder. Properties: Count, Item. Methods: This object does not support any methods. FileSystemObject Provides scripts with access to the file system. Properties: Drives. Methods: BuildPath, CopyFile, CopyFolder, CreateFolder, CreateTextFile, DeleteFile, DeleteFolder, DriveExists, FileExists, FolderExists, GetAbsolutePathName, GetBaseName, GetDrive, GetDriveName, GetExtensionName, GetFile, GetFileName, GetFolder, GetParentFolderName, GetSpecialFolder, GetTempName, MoveFile, MoveFolder, OpenTextFile. Folder Provides scripts with access to folder properties. Properties: Attributes, DateCreated, DateLastAccessed, DateLastModified, Drive, Files, IsRootFolder, Name, ParentFolder, Path, ShortName, ShortPath, Size, SubFolders, Type. Methods: Copy, Delete, Move, OpenAsTextStream. Folders Collection Provides scripts with access to folders located within another folder. Properties: Count, Item. Methods: Add. TABLE 3.4 VBSCRIPT RUN-TIME O BJECTS ( CONTINUED) Properties Like WSH objects, the VBScript run-time objects support a large number of properties. Table 3.5 provides a complete list of VBScript run-time properties. Property Name Description AtEndOfLine Returns a value of either true or false based on whether the file pointer has reached the TextStream file’s end-of-line marker AtEndOfStream Returns a value of either true or false based on whether the end of a TextStream file has been reached Attributes Modifies or retrieves file and folder attributes AvailableSpace Retrieves the amount of free space available on the specified drive TABLE 3.5 VBSCRIPT RUN-TIME P ROPERTIES (continues) 76 Microsoft WSH and VBScript Programming for the Absolute Beginner, Second Edition Property Name Description Column Retrieves the current column position in a TextStream file CompareMode Sets or returns the comparison mode used to compare a Dictionary object’s string keys Count Returns a value representing the number of the items in a collection or Dictionary object DateCreated Retrieves a file or folder’s creation date and time DateLastAccessed Retrieves the date and time that a file or folder was last accessed DateLastModified Retrieves the date and time that a file or folder was last modified Drive Retrieves the drive letter where a file or folder is stored DriveLetter Retrieves the specified drive’s drive letter Drives Establishes a Drives collection representing all the drives found on the computer DriveType Returns a value identifying a drive’s type Files Establishes a Files collection to represent all the File objects located within a specified folder FileSystem Retrieves the name of the file system used on the specified drive FreeSpace Retrieves the amount of free space available on the specified drive IsReady Returns a value of either true or false based on the availability of the specified drive IsRootFolder Returns a value of either true or false based on whether the specified folder is the root folder Item Retrieves or sets an item based on the specified Dictionary object key Key Sets a Dictionary object key Line Retrieves the current line number in the TextStream file Name Gets or modifies a file or folder’s name ParentFolder Returns a reference to the specified file or folder’s parent folder object Path Retrieves the path associated with the specified file, folder, or drive RootFolder Retrieves the Folder object associated with the root folder on the specified drive SerialNumber Retrieves the specified disk volume’s serial number ShareName Retrieves the specified network drive’s share name ShortName Retrieves the specified file or folder’s 8.3-character short name TABLE 3.5 VBSCRIPT RUN-TIME P ROPERTIES (CONTINUED) Methods VBScript run-time objects also support a larger number of methods, which you will find essen- tial when working with the Windows file system. These methods are outlined in Table 3.6. 77 Chapter 3 • VBScript Basics Property Name Description ShortPath Retrieves a file or folder’s short pathname associated with a file or folder’s 8.3-character name Size Returns the number of bytes that make up a file or folder SubFolders Establishes a Folders collection made up of the folders located within a specified folder TotalSize Retrieves a value representing the total number of bytes available on a drive Type Retrieves information about the specified file or folder’s type VolumeName Gets or modifies a drive’s volume name TABLE 3.5 VBSCRIPT RUN-TIME P ROPERTIES (CONTINUED) Method Name Description Add (Dictionary) Adds a key and item pair to a Dictionary object Add (Folders) Adds a Folder to a collection BuildPath Appends a name to the path Close Closes an open TextStream file Copy Copies a file or folder CopyFile Copies one or more files CopyFolder Recursively copies a folder CreateFolder Creates a new folder CreateTextFile Creates a file and a TextStream object so that it can be read from and written to Delete Deletes a file or folder DeleteFile Deletes a file TABLE 3.6 VBSCRIPT RUN-TIME M ETHODS (continues) 78 Microsoft WSH and VBScript Programming for the Absolute Beginner, Second Edition Method Name Description DeleteFolder Deletes a folder’s contents DriveExists Returns a value of true or false based on whether a drive exists Exists Returns a value of true or false based on whether a key exists in a Dictionary object FileExists Returns a value of true or false based on whether the specified file can be found FolderExists Returns a value of true or false based on whether the specified folder can be found GetAbsolutePathName Retrieves a complete pathname GetBaseName Retrieves a file name without its file extension GetDrive Returns the Drive object associated with the drive in the specified path GetDriveName Returns the name of a drive GetExtensionName Returns a file’s extension GetFile Returns a File object GetFileName Returns the last file name or folder of the specified path GetFileVersion Returns a file’s version number GetFolder Returns the Folder object associated with the folder in the specified path GetParentFolderName Returns the name of the parent folder GetSpecialFolder Returns a special folder’s name GetTempName Returns the name of a temporary file or folder Items Returns an array where items in a Dictionary object are stored Keys Returns an array containing the keys in a Dictionary object Move Moves a file or folder MoveFile Moves one or more files MoveFolder Moves one or more folders OpenAsTextStream Opens a file and retrieves a TextStream object to provide a reference to the file OpenTextFile Opens a file and retrieves a TextStream object to provide a reference to the file Read Returns a string containing a specified number of characters from a TextStream file TABLE 3.6 VBSCRIPT RUN-TIME M ETHODS ( CONTINUED) Using VBScript Run-Time Objects in Your Scripts Now seems like a good time to look at an example of how to incorporate the VBScript FileSystemObject into your scripts and use its properties and methods to work with the Windows file system. Take a look at the following script: ‘************************************************************************* ‘Script Name: FreeSpace.vbs ‘Author: Jerry Ford ‘Created: 11/22/02 ‘Description: This script demonstrates how to use VBScript run-time ‘objects and their properties and methods. ‘************************************************************************* ‘Initialization Section Option Explicit Dim FsoObject, DiskDrive, AvailSpace 79 Chapter 3 • VBScript Basics Method Name Description ReadAll Reads the entire TextStream file and its contents ReadLine Reads an entire line from the TextStream file Remove Deletes a Dictionary object’s key, item pair RemoveAll Deletes all Dictionary object’s key, item pairs Skip Skips a specified number of character positions when processing a TextStream file SkipLine Skips an entire line when processing a TextStream file Write Places a specified string in the TextStream file WriteBlankLines Writes a specified number of newline characters to the TextStream file WriteLine Writes the specified string to the TextStream file TABLE 3.6 VBSCRIPT RUN-TIME M ETHODS ( CONTINUED) . Copyright information • Contact or support information Microsoft WSH and VBScript Programming for the Absolute Beginner, Second Edition The rest of the template is divided into three sections. • Initialization. amount of free space available on the specified drive TABLE 3.5 VBSCRIPT RUN-TIME P ROPERTIES (continues) 76 Microsoft WSH and VBScript Programming for the Absolute Beginner, Second Edition Property. because VBScript also assigns a special meaning to them. Some of these words are reserved because they are part of the language itself, and others are reserved for future use. Table 3.2 lists VBScript s