On Tue, Mar 15, 2005 at 07:54:38PM +0530, Asif, M wrote:
> Hello Jeremy,
>
> Thanks for your response.
>
> I tried the following
>
> On Windows side, an MFC application with the code given below access the
> file using the samba share.
>
>
> CString strFile =
> _T("\\\\180.144.1.11\\netmbase\\tmp\\test.txt");
> CStdioFile fValueFile;
> if (!fValueFile.Open( strFile ,CFile::modeWrite |
> CFile::shareExclusive ) )
> {
> wcout<<_T("Open failed")<<endl;
> }
> else
> {
> //wcout<<_T("Open Success")<<endl;
> }
>
> fValueFile.WriteString( strt );
> getchar()
>
> fValueFile.Close();
>
> On UNIX side, code is something similar to this
>
> int fid =
> open("/export/home/scsd13/kiran/NetMBase/tmp/test.txt", O_RDWR|O_EXCL ) ;
> if( 0 > fid )
> {
> perror("open"),exit(1);
> }
>
> struct flock lockDetails ;
> lockDetails.l_start = 0 ;
> lockDetails.l_whence = SEEK_SET;
> lockDetails.l_len = 0 ;
> lockDetails.l_type = F_WRLCK ;
> int nErr = fcntl( fid, F_SETLK, &lockDetails);
> if( 0 > nErr )
> {
> perror("lock"),exit(1);
> }
> getchar();
> close(fid);
>
> Now,
>
> 1. Two instances of the executable runs on Windows side, open fails with
> sharing violation if the first one is not released ( blocked at getchar()
> call) , no problem.
> 2. Same is the case with two instances of UNIX processes.
> 3.The unix process locks the file and does not release it (blocked at
> getchar() ), and then the windows client is executed, WriteString throws an
> exceptoin giving error 33(locked by other process). No problem 4. Now if the
> Windows client opens the file first (blocked at getchar() ) and then the
> unix client is invoked, the fcntl call succeeds...
>
> I tried lockf() instead of fcntl(), turned on mandatory locking etc, but
> with no success.
>
> Am I missing out some thing? Is there an easier way for getting this work?
> Basically, I want to ensure that there is no read happening when any one
> (from unix or windows) is writing into the file an vice versa.
What OS are you running on ? This code will work on Linux with kernel
oplocks, and if you turn off oplocks should work on other UNIXes.
Jeremy.
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