KB139548 - How to Use the GetDiskFreeSpace API Call

Article ID: 139548

Article Last Modified on 7/30/1999

Microsoft Visual FoxPro 3.0 Standard Edition

This article was previously published under Q139548

SUMMARY

By using the GetDiskFreeSpace API call, you can determine how much disk space a drive has, how much is used, and how much is free. This article explains how to use and call the Win32 GetDiskFreeSpace API.

MORE INFORMATION

In many cases, such as backing up or restoring user data, you need to know various characteristics about the media with which you are working (such as whether or not it is fixed or removable) and about the amount of available space on that media.

By using the GetDiskFreeSpace API call, you can derive the low-level information about the disk (such as bytes per sector and sectors per cluster), and then use that information for your calculations.

The following code demonstrates the syntax and use of this API call and gives some of the more common calculations you may need to perform.

Code Sample

**---------------------------------------------------------------**
** Program: Getspace.prg                                         **
** Purpose: Demonstrates how to declare and call the Win32       **
**          GetDiskFreeSpace API.                               **
**---------------------------------------------------------------**
PUBLIC  lpRootPathName, ;
        lpSectsPerCluster, ;
        lpBytesPerSector, ;
        lpNumberOfFreeClusters, ;
        lpTotalNumberOfClusters

lpRootPathName       = "A:\"
lpSectsPerCluster    = 0
lpBytesPerSect       = 0
lpNumOfFreeClusters  = 0
lpTotNumOfClusters   = 0

DECLARE INTEGER GetDiskFreeSpace IN Win32API AS GetDiskSpace ;
        STRING  @lpRootPathName, ;
        INTEGER @lpSectsPerCluster, ;
        INTEGER @lpBytesPerSect, ;
        INTEGER @lpNumOfFreeClusters, ;
        INTEGER @lpTotNumOfClusters

RetVal=GetDiskSpace(@lpRootPathName, @lpSectsPerCluster, @lpBytesPerSect, ;
        @lpNumOfFreeClusters, @lpTotNumOfClusters)

DEFINE WINDOW ShowInfo FROM 0,0 TO 12,70 ;
        FLOAT CLOSE ;
        TITLES "Drive Information for " + ;
        ALLTRIM(lpRootPathName) ;
        FONT "Courier",10

ACTIVATE WINDOW ShowInfo
MOVE WINDOW ShowInfo CENTER

@ 0,1 SAY "Drive & path name            : " + ;
   ALLTRIM(lpRootPathName)
@ 1,1 SAY "Sectors per cluster          : " + ;
   ALLTRIM(STR(lpSectsPerCluster))
@ 2,1 SAY "Bytes per Sector             : " + ;
   ALLTRIM(STR(lpBytesPerSect))
@ 3,1 SAY "Number of free clusters      : " + ;
   ALLTRIM(STR(lpNumOfFreeClusters))
@ 4,1 SAY "Total number of clusters     : " + ;
   ALLTRIM(STR(lpTotNumOfClusters))
@ 5,1 SAY "==================================================="
@ 6,1 SAY "Total disk space             : " + ;
   ALLTRIM(STR(lpSectsPerCluster * lpBytesPerSect * lpTotNumOfClusters))
@ 7,1 SAY "Free disk space              : " + ;
   ALLTRIM(STR(lpSectsPerCluster * lpBytesPerSect * lpNumOfFreeClusters))
@ 8,1 SAY "Used disk space              : " + ;
   ALLTRIM(STR(lpSectsPerCluster * lpBytesPerSect * ;
   (lpTotNumOfClusters - lpNumOfFreeClusters)))

**--------------------------<End Code>---------------------------**

When this code is run on a 1.44-megabyte floppy disk, the following output is what you would get if the floppy disk is a new, formatted floppy disk that contains no data:

Drive & path name        : A:\ 
Sectors per cluster      : 1
Bytes per sector         : 512
Number of free clusters  : 2847
Total number of clusters : 2847
===================================
Total disk space         : 1457664
Free disk space          : 1457664
Used disk space          : 0

Using this API call, you can quickly and easily determine how much disk space you have available for your program. A related disk API (GetVolumeInformation) provides information about the disk physical characteristics such as the file system and file compression.

For additional information on this API function, please see the "GetDiskFreeSpace" topic in the Win32API help file. Note that this help file is available only on the compact disc version of Visual FoxPro; it is not shipped with the disk version. For more information, please see the following article in the Microsoft Knowledge Base:

139172 PRB: Visual FoxPro CD-ROM Compact Disc Includes Extra Files

For information about the DECLARE - DLL command, please search the Visual FoxPro Help file.

Additional query words: VFoxWin drive volume space free attributes

Keywords: kbcode KB139548