Disk Operating System Commands in VBA.
The Microsoft Disk Operating System (MS-DOS 1.0) was launched in 1982. The first edition of the Microsoft Windows 1.0 Operating System, Disk Operating System with Graphical User Interface (GUI), was released on November 20, 1985 – Source: www.wikipedia.org. The Disk Operating System Version under Windows 7 is 6.1.7600.
Disk Operating System Commands (both Internal and External) are used in the Command Prompt for Managing Files and folders on Disks, and for retrieving information about them.
DIR Command.
For example, the Directory Command (Dir /S/B/P) provides a file list with full Path Names (like 'C:\My Documents\New Folder\Resume.doc') from your C: Drive and displays them on screen, one page at a time.
Let us try an example.
Click on the Start Menu.
Type cmd and press Enter; the DOS Window will open up with the Command Prompt C:\>. Type the following command to display a list of Folders and Files from your C: drive, one page at a time. You must press a key to advance to the next.
Warning: The Folders/Files listing on your C: drive may run to hundreds of pages. Press Ctrl+C (break the command) to terminate the list from displaying further.
C:\> Dir /S/B/P
C:\>> is the command prompt
Dir (command stands for Directory)
The Command switch /S includes Files in subdirectories in the output.
The Command switch /B provides a bare-formatted list of files, i.e., gives only the file Path names without creation date, file sizes, or any other information about the files.
The Command switch /P displays the output on Screen one Page (one screen full) at a time. Need to press a key on the keyboard to advance the files list to the next Page.
If you want to save the entire list to a text file, without page breaks, issue the following command with the output redirection symbol (>) and a text File name. The redirection symbol will send the output of the Directory command to a specified text file, without displaying it on the screen.
C:> Dir /S/B > myDirList.txt
Note: Leave a space on either side of the > symbol.
TYPE and MORE Command.
Open myDirList.txt file in Notepad and check the contents. You can display the contents of the myDirList.txt file with the following DOS Command:
C:\> TYPE myDirList.txt
Press Ctrl+C to stop the runaway display. The TYPE command displays the contents of a text file on screen. But it will not display the output one screen full at a time. To do that, we can use another DOS command: MORE, both Commands joined with the piping symbol (|).
C:\> TYPE myDirList.txt | MORE
In the above command, the piping symbol (|) is used to join the TYPE filename.txt | MORE commands to get the required output. The TYPE command reads the text file Contents and passes it to the next command, MORE, without directly sending the output to the Screen. The MORE Command takes its input from the TYPE command and displays it one screen-full at a time. Press SPACEBAR to display the next screen-full of text.
OR
C:\> MORE < myDirList.txt
If the > (greater than) symbol is known as a redirection symbol in DOS, then the < (less than) symbol is known as a Source symbol for the MORE command. The MORE command reads data from the filename given immediately after the Source Symbol (<) and displays one screen-full at a time.
DIR Command in VBA.
The Dir Command is available in VBA too. But it is used for a different purpose. We can use this command to check for a particular file or the presence of any file in a folder. The usage of this command is shown below:
strOutput = Dir("C:\My Documents\Resume.doc", vbNormal)
The Dir command checks for the Word File Resume.doc in the Folder C:\My Documents. If found, the file name 'Resume.doc' is returned in the strOutput Variable; otherwise, an empty String is returned.
strOutput = Dir("C:\My Documents\*.*", vbNormal)
This command gets the first file name from the specified folder, and returns it in the strOutput Variable. You may try out this command in the Debug Window directly, like:
? Dir("C:\My Documents\*.*")
This will print the first file name found in the folder C:\My Documents in the Debug Window. To get subsequent file names from the same folder, you can run the command without any parameters to the function, like:
? Dir()
Note: The First time you run this Command, you should provide a Path as a parameter; otherwise, it will run into an error.
Place the insertion point on the Dir() Command, and press F1 to display the details of this Command in Access Help Documents.
There are other interesting Disk Operating System Commands, like ChDrive, ChDir, MkDir, RmDir, etc., and we will learn their usage in VBA Next week.
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