Hi Justin! On 24 Sep., 00:04, "Justin C. Walker" <jus...@mac.com> wrote: > For most unix-like systems, it's generally not true that a close() of a file > descriptor will wait until the file is closed.
Thank you, that's good to know! Then it seems more than likely to me that there's the problem with the expect interface. > > Would it make sense to call os.fsync(F) after F.close()? > > I would think that doing this will only cause an error of some sort to be > handed to your code: 'F' is not associated with anything after the close, so > "os.sync(F)" would be essentially meaningless to the kernel. Sure, I meant to catch the ValueError that is raised when the file really is done. But do I understand correctly that os.sync(F) will either raise a ValueError orr wait until F.close() is completed? > To your problem with corruption, if you are opening a new file descriptor for > a file that you are writing with an existing file descriptor, you are asking > for trouble, ... It is not *I* who is asking for trouble here: The code that I posted above is from sage/interfaces/expect.py. > You write to the file descriptor > Python holds onto the data for a while > You open a new descriptor on the same file > Python reads in what's there I guess that is exactly what's happening in the Gap, Singular,... interfaces: - If one has a big string s, then singular(s) will not directly send s to the singular interface, but eventually singular._eval_line_using_file(s) is called.In that method, the file singular._local_tmpfile() is opened for writing, s is written to it, then it is closed. - Directly after closing the file, it is read into Singular. I could imagine that sometimes it is attempted to read it before closing it succeeded. - Moreover, if the next large input line occurs, then singular._local_tmpfile() is again opened for writing -- perhaps before the previous I/O to it was completed? > I don't know enough about the rest of the system or your code to be sure this > is what's happening. If you haven't already, try F.sync() (or os.sync(F)) > before closing the file. So, better before than afterwards. Makes sense. > Another hack: try pausing before accessing the file after the close, so > you're (more) sure that the close has had an effect before proceeding. I doubt that it would be acceptable to slow down every single call to an expect interface by pausing. Best regards, Simon -- To post to this group, send an email to sage-devel@googlegroups.com To unsubscribe from this group, send an email to sage-devel+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URL: http://www.sagemath.org
