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An ASP Disk Space Monitor
A previous article describes how to use the
Drives collection to access information about disk drives attached to an ASP web server.
This article expands on the ideas presented in that article by describing how to create a
dynamic disk space monitor. The techniques used here could be used to ensure that there is
enough disk space before a user uploads a large file to the server, or perhaps the code
could be used to help create a web based server monitoring tool so that the server
administrator can keep a track of server resources when miles from home.
The typical output from this script is shown in the image below. For each
accessible drive connected to the system, the drive letter is printed, together with the
drive’s volume name (if it has one). The amount of used space on a disk is shown in
red, free space shown in blue. This effect is created by resizing red and blue GIF images
to give a representation of the total amount of disk space on a given drive. Additionally,
the images’ ALT tags have been set up so that they give the amount of disk space (in
the example below, the ALT tag for the C: drive’s free space shows that there is
227.1Mb of free disk space).
If you want the images used above, they are available in a ZIP file which is linked
from the bottom of this article.
Dissecting the Script
The first line of code creates a FileSystemObject object. This is a powerful object
when used with ASP – its most common use is for reading and writing text files on the
server, but here the Drives property is used to find out information about the drives
connected to the server:
Set FileSystemObject =
Server.CreateObject("Scripting.FileSystemObject")
The following line of code establishes the Drives object as a Drives collection:
Set Drives = FileSystemObject.Drives
The Drives collection will contain information about all of the drives connected to the
server, so a For Each … Next loop is used to loop through each member of the Drives
collection:
For Each DiskDrive in Drives
One thing to remember is that although a drive is connected to a server, it may not be
accessible. The script will generate errors if it attempts to access certain drive
properties if that drive is not ready. Removable media such as a floppy, CD-ROM or ZIP
drives will not be accessible unless there are disks in the drives. Fortunately, the
IsReady property of each drive can be used to check that the drive is ready:
If DiskDrive.IsReady Then
From the TotalSize and FreeSpace drive properties, it is possible to work out the
amount of disk space in use on that drive:
totalspace = DiskDrive.TotalSize
freespace = DiskDrive.FreeSpace
usedspace = totalspace - freespace
Disk space is reported as bytes, so the following code will convert the space to Mb. It
will also convert free and used space as a percentage of the total space on a drive:
freepercent = Int((freespace/totalspace)*100)
freemb = Int((freespace/1024)/1024)
usedmb = Int((usedspace/1024)/1024)
usedpercent = Int((usedspace/totalspace)*100)
The following code is used to format the text that will be used for the ALT tags that
display disk space. To make the display look nicer, it shows space less than 1 Mb in size
as Kb, and space greater than 1024 Mb as Gb. The FormatNumber function is used to specify
the number of decimal places that the numbers should be rounded to:
If freespace =< 1048576 Then
freelabel = FormatNumber(freespace/1024, 1) & " Kb"
Elseif freespace =< 1073741824 then
freelabel = FormatNumber((freespace/1024)/1024, 1) & " Mb"
Else
freelabel = FormatNumber(((freespace/1024)/1024)/1024, 2) & " Gb"
End If
If usedspace =< 1048576 Then
usedlabel = FormatNumber(usedspace/1024, 1) & " Kb"
Elseif usedspace =< 1073741824 Then
usedlabel = FormatNumber((usedspace/1024)/1024, 1) & " Mb"
Else
usedlabel = FormatNumber(((usedspac e/1024)/1024)/1024, 2) & " Gb"
End If
There is also a bit of a hack for drives that have no free or used space – this is
reported as 0 bytes:
If Left(freelabel,3) = "0.0" Then freelabel = "0 bytes"
If Left(usedlabel,3) = "0.0" Then usedlabel = "0
bytes"
The ALT tags for the free and used space are then prepared:
used_alt_tag = "Drive " & DiskDrive.DriveLetter & ": " & usedlabel
& " in use"
free_alt_tag = "Drive
" & DiskDrive.DriveLetter & ": " & freelabel & " free"
The drive letter and (if it has one) volume name are then output using Response.Write
statements:
Response.Write "Drive " & DiskDrive.DriveLetter & ": "
If DiskDrive.VolumeName <> "" then
Response.Write "["
& DiskDrive.VolumeName & "] : "
End If
Further Response.Write statements are then used to display the graphical representation
of disk space. Note that the width of the free and used space indicators are altered
according to the percentage calculated earlier. The actual image is composed of four
elements: a left border, the used space indicator, the free space indicator, and finally
the right border.
Response.Write "<img
align=absmiddle src=bb-drives-diskindicator-leftborder.gif>"
Response.Write "<img align=absmiddle
src=bb-drives-diskindicator-used.gif width=" &
usedpercent & " height=29 alt=" & Chr(34) & used_alt_tag & Chr(34) & ">"
Response.Write "<img align=absmiddle src=bb-drives
-diskindicator-free.gif width=" & (100-usedpercent)
& " height=29 alt="
& Chr(34) & free_alt_tag & Chr(34) & ">"
Response.Write "<img align=absmiddle
src=bb-drives-diskindicator-rightborder.gif>"
Response.Write "<br>"
The next two lines of code will allow the script to proceed to the next drive in the
Drives collection:
End If
Next
The final lines of code release the created objects from system memory:
Set Drives = nothing
Set FileSystemObject = nothing
And that’s it. Hopefully you should be able to find a use for the script
don’t hesitate to email me if you find an interesting use
for it.
For convenience, the entire code for the script is given below.
The entire code for the disk monitoring script
<%
'An ASP disk space monitoring script
'See http://www.brettb.com/ASPDiskMonitoringScript.asp
'Create a FileSystemObject object
Set FileSystemObject =
Server.CreateObject("Scripting.FileSystemObject")
Set Drives = FileSystemObject.Drives
'Step through the drives collection, and extract information
about any drive that is ready
For Each DiskDrive in Drives
If DiskDrive.IsReady Then
'The following lines work out the amount of used and free
space on a disk. ASP reports disk space in bytes.
'Divide bytes by 1024 to get Kb, Kb by 1024 to get Mb, and so on...
totalspace = DiskDrive.TotalSize
freespace = DiskDrive.FreeSpace
usedspace = totalspace - freespace
freepercent = Int((freespace/totalspace)*100)
freemb = Int((freespace/1024)/1024)
usedmb = Int((usedspace/1024)/1024)
usedpercent = Int((usedspace/totalspace)*100)
'If the amount of disk space is below one Mb then report
freespace as Kb.
'A similar thing is done for Mb and Gb of space.
If freespace =< 1048576 Then
freelabel = FormatNumber(freespace/1024, 1) & " Kb"
Elseif freespace =< 1073741824 then
freelabel = FormatNumber((freespace/1024)/1024, 1) & " Mb"
Else
freelabel = FormatNumber(((freespace/1024)/1024)/1024, 2) & " Gb"
End If
If usedspace =< 1048576 Then
usedlabel = FormatNumber(usedspace/1024, 1) & " Kb"
Elseif usedspace =< 1073741824 Then
usedlabel = FormatNumber((usedspace/1024)/1024, 1) & " Mb"
Else
usedlabel = FormatNumber(((usedspace/1024)/1024)/1024, 2) & " Gb"
End If
If Left(freelabel,3) = "0.0" Then freelabel = "0
bytes"
If Left(usedlabel,3) = "0.0" Then usedlabel = "0
bytes"
used_alt_tag = "Drive
" & DiskDrive.DriveLetter & ": " & usedlabel & " in use"
free_alt_tag = "Drive
" & DiskDrive.DriveLetter & ": " & freelabel & " free"
Response.Write "Drive
" & DiskDrive.DriveLetter & ": "
If DiskDrive.VolumeName <> "" then
Response.Write "["
& DiskDrive.VolumeName & "] : "
End If
'Create the graphical representation of the freespace
Response.Write "<img
align=absmiddle src=bb-drives-diskindicator-leftborder.gif>"
Response.Write "<img align=absmiddle
src=bb-drives-diskindicator-used.gif width=" &
usedpercent & " height=29 alt=" & Chr(34) & used_alt_tag & Chr(34) & ">"
Response.Write "<img align=absmiddle
src=bb-drives-diskindicator-free.gif width=" &
(100-usedpercent) & " height=29 alt=" & Chr(34) & free_alt_tag & Chr(34) & ">"
Response.Write "<img align=absmiddle
src=bb-drives-diskindicator-rightborder.gif>"
Response.Write "<br>"
End If
Next
Set Drives = nothing
Set FileSystemObject = nothing
%>
Images used by the Disk Monitoring Script
If you would like the four images used with this script (created using Kai's Power
Tools 5), then download this ZIP file.
Further Reading
Useful Development Tools
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