On mardi 07 octobre 2008, Rolf-Werner Eilert wrote: > For my apps in Gambas, I use lockfiles, not folders, to lock a certain > file. Experience told me that "sometimes" when two users/processes want > to access the same file, these may overlap. So I added an identification > method and a time delay in case of locks. This is what it looks like > (kinda prototyped): > > WHILE Exist(theLockFile) THEN > > OPEN theLockFile FOR READ ... > LINE INPUT firstLine > CLOSE ... > > IF firstLine = myOwnName THEN 'old lock file from myself: > KILL theLockFile 'may be deleted, then proceed > > ELSE 'lock file from someone else: > WAIT one second > > WEND > > 'now first of all, write my own lockfile > 'then begin reading the file I want > 'finally delete lockfile > > This is how this looks in practice: > > WHILE Exist(pfad &/ "klassenbuch.block") > OPEN pfad &/ "klassenbuch.block" FOR READ AS #dtnr > LINE INPUT #dtnr, t$ > CLOSE #dtnr > IF t$ = system.User THEN > KILL pfad &/ "klassenbuch.block" > ELSE > WAIT 1 > END IF > WEND > > > OPEN pfad &/ "klassenbuch.block" FOR WRITE CREATE DIRECT AS #dtnr > PRINT #dtnr, system.User > CLOSE #dtnr > > OPEN karteiVerz &/ jg &/ "klassenbuch" FOR READ AS #dtnr > > and so on. While I am writing this email, I find that this has one big > drawback: If the lock file was made by someone else and that app > crashed, my program will wait forever for the lockfile to disappear. So > one should add a counter, e. g. 5 seconds, to stop waiting. > > Regards > > Rolf >
So, use the LOCK instruction to create a system-wide mutually exclusive code section! -- Benoit Minisini ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Gambas-user mailing list Gambas-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/gambas-user
