This may not be what you are looking for, but if you were
to name the files in a way that uses the date, then
you can just delete the old ones the next day.
Joe.
On May 28, 2006, at 5:34 PM, wren ng thornton wrote:
--- Chris Devers wrote:
Really??
In my experience, the `open` command immediately
returns control to the controlling process (the
shell,
or whatever else invoked it (pine etc)) without
waiting for the `open`ed application to finish, or
for
that matter even to finish launching.
Others have gone over briefly why your observations
about `open` returning are correct, but why that's
actually the root of the problem. The problem isn't
that it takes too long to return, it's that it returns
too quickly. The issue in general is race conditions.
Because `open` returns so soon you have no idea when
the other app will open the file let alone close it.
If you delete the file right away it may be missing by
the time the app is up and running; if you delete it
after it's been opened but before it's been closed,
the app may choose to "undelete" it for you by saving
it or whatnot.
The only real way around this problem is to wait for
the app to close and only then delete the file, and
the only way to get that information without race
conditions itself is from the OS itself. You'll want
the new process to be a child process so you can know
definitively that it has completed (and without
constantly polling the process table). system() does
this, though you'll want to launch the app directly
rather than using something like `open` to open it
indirectly.
Since terminated processes can't have open files you
can be sure that once the child finishes, the file is
closed (or at least closed as far as your program is
concerned, other processes out there in the universe
may muck with your plans to delete it, but you have no
control over that).
In short, `open` is an awesome utility that I wish all
*nices had, but it's not the right tool for this job.
Live well,
~wren
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