I'm sorry, I don't remember if this problem was occuring under unix or windows. The following response applies to unix The OPENSEQ doesn't prevent other people from opening/changing/deleting the file. In general, there's nothing in unix that prevents you from deleting an open file either. The file gets unlinked from the directory where it had been deleted from, but the inode continues to exist and the file remains accessable to anyone who already had it open. When the last person closes the file, the inode goes away. I seem to remember that universe, and maybe unidata, had a table of open files, and it would close and reopen unix files as necessary to avoid running out of OS file handles. Is it possible that that is happening here? Unidata closes the unix file, and then tries to reopen it so that it can do the write, and fails because it has been deleted?
-----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Kevin King Sent: Monday, December 20, 2004 10:56 AM To: [EMAIL PROTECTED] Subject: RE: [U2] Writeseq quirkiness - the answer That's something of a mystery to me too. The app that Dana is referring to is a java app that polls the directory and then consumes anything it finds. I found it interesting that the Java app could open a file that was being written to by Unidata, but then again, we've seen this with credit card processing so I figured the .tmp -> .out rename might be a workable solution in this case as well. -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of David Wolverton Sent: Monday, December 20, 2004 9:19 AM To: [EMAIL PROTECTED] Subject: RE: [U2] Writeseq quirkiness - the answer One question - why could Kevin's process delete an open file? I thought the OS prevented that very situation from happening! Or does UD not hold the item open such that the OS sees it an 'in use by another process'? It would seem that by virtue of doing OPENSEQ, no one could 'delete' the item until you wrote the item (or did CLOSESEQ)... -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Dana Baron Sent: Monday, December 20, 2004 8:39 AM To: U2-Users (E-mail) Subject: [U2] Writeseq quirkiness - the answer Greetings, And the prize goes to Kevin King! He came up with the "write" answer to solve my writeseq problem. Of course, he had an advantage since he helped write the application in the first place. Still, I was stumped and his answer worked. Thank you (once again!), Kevin. For those who care: To understand the solution, you need a little more background. The code segment I sent is part of an application that manages the interface between my Unidata application and a third-party device, which in turn manages the interface with a bunch of other devices. When I want to send data out of my application, I create a file with a .out extension and write the appropriately formatted data to the file. A program written by Kevin King sits out there looking for files with .out extensions. When it finds one, it reads the file and sends the data to the third-party device. It then deletes the file. And this is wherein lay the problem, and the solution. What was happening was, my program would open the file (OPENSEQ) and Kevin's program would come along and try to read it, then delete it, then I'd try to write to it (WRITESEQ), but by then it was gone. I changed the code a little bit to open the file with a .tmp extension, write to that, then rename it to .out. Works great! There are still a few mysteries: why does the original code work for just about every situation, then suddenly fail for one new situation that is seemly the same as all the others? But heck, it works so I'll go with it. Thanks to everyone who responded with a solution. And the u2 list comes through again! Dana Baron System Manager Smugglers' Notch Resort ------- u2-users mailing list [EMAIL PROTECTED] To unsubscribe please visit http://listserver.u2ug.org/ ------- u2-users mailing list [EMAIL PROTECTED] To unsubscribe please visit http://listserver.u2ug.org/ ------- u2-users mailing list [EMAIL PROTECTED] To unsubscribe please visit http://listserver.u2ug.org/ ------- u2-users mailing list [EMAIL PROTECTED] To unsubscribe please visit http://listserver.u2ug.org/
