DO decl
 
#DEFINE GENERIC_READ 0x80000000
#DEFINE GENERIC_WRITE 0x40000000
#DEFINE cret  Chr(13)
#DEFINE dcret Chr(13)+Chr(13)
 
    LOCAL lcPath, lcAlias, lcFile, hFile, lnHeader, lcBuffer
    lcPath  = GetTmpPath()
    lcAlias = "Test"
    lcFile  = lcPath + lcAlias + ".dbf"
 
    * creating a testing table
    IF USED (lcAlias)
        USE IN (lcAlias)
    ENDIF
 
    IF Not FILE(lcFile)
        SET SAFETY OFF
        CREATE TABLE (lcFile) (dt T)
        SET SAFETY ON
        INSERT INTO (lcAlias) VALUES (datetime())
    ELSE
        USE (lcFile) ALIAS (lcAlias) SHARED
    ENDIF
 
    lnHeader = HEADER()
    USE IN (lcAlias)
 
    lcBuffer = REPLI (Chr(0), 250)
    hFile = OpenFile (lcFile, @lcBuffer, GENERIC_READ)
 
    IF LockFile (hFile, 0,0, lnHeader,0) <> 0
        = MessageB ("File " + lcFile + " is locked." + dcret +;
            "At this point do not close this Dialog " +;
            "and start another VFP instance." + dcret +;
            "Use another instance to open " + lcFile + cret +;
            "or just try to read the tables on " + lcPath + " " + ;
            "using regular DIRECTORY command." + dcret +;
            "After that click Ok to unlock the target file.", 64, "Locking a file")
 
        = UnlockFile (hFile, 0,0, lnHeader,0)
    ELSE
        * 6 = ERROR_INVALID_HANDLE - already in exclusive use
        ? "Error code:", GetLastError()
    ENDIF
    = CloseHandle (hFile)
 
FUNCTION  GetTmpPath
    LOCAL lpBuffer, lnLength
    lpBuffer = SPACE(250)
    lnLength = GetTempPath (LEN(lpBuffer), @lpBuffer)
RETURN Iif (lnLength=0, "C:\Temp", PADR(lpBuffer, lnLength))
 
PROCEDURE  decl
    DECLARE INTEGER GetLastError IN kernel32
 
    DECLARE INTEGER GetTempPath IN kernel32;
        INTEGER nBufferLength, STRING @ lpBuffer
 
    DECLARE INTEGER LockFile IN kernel32;
        INTEGER hFile, INTEGER dwFileOffsetLow,;
        INTEGER dwFileOffsetHigh,;
        INTEGER nNumberOfBytesToLockLow,;
        INTEGER nNumberOfBytesToLockHigh
 
    DECLARE INTEGER UnlockFile IN kernel32;
        INTEGER hFile, INTEGER dwFileOffsetLow,;
        INTEGER dwFileOffsetHigh,;
        INTEGER nNumberOfBytesToUnlockLow,;
        INTEGER nNumberOfBytesToUnlockHigh
 
    DECLARE INTEGER OpenFile IN kernel32;
        STRING   lpFileName,;
        STRING @ lpReOpenBuff,;
        INTEGER  wStyle
 
    DECLARE INTEGER CloseHandle IN kernel32;
        INTEGER hObject