On Jan 29, 2011, at 8:01 AM, Robert DuToit wrote: > On Jan 29, 2011, at 5:15 AM, Ken Thomases wrote: > >> You should definitely not be creating subprocesses to run 'tail' or 'ps'. >> 'tail' is just a file reader, and your app can directly open and read the >> file. To monitor whether rsync is still running, you may be able to use the >> techniques illustrated in these articles: > > I know - I didn't see any easy way to directly read in just some last lines > of the log as 'tail' does assuming you don't want to read in 1 million lines > of a log every fraction of a second and then parse. I'll research this more.
You shouldn't open the file and read from the beginning every time. Open the file once after rsync creates it, then read some data (perhaps up to the then-current end of file) and parse it, keeping in mind that the final line may be incomplete. At the next firing of your timer, clear the end-of-file marker and read some more. Append the new data to whatever partial line was left over from the last time. Etc. >> It may also be possible to use a pipe to the rsync process not for >> communicating its output but just to monitor its lifetime. If you redirect >> most of rsync's output to a file (e.g. using the --log-file option), then >> you can monitor its stdout (and/or stderr) from your app. When it closes, >> the process has presumably exited. > > I hadn't thought of that - I was redirecting the stdout in the Helper Tool > using a timer to poll the log but never thought of the rsync option itself! > I'll have to check this out. That would do away with the ps call nicely. > Isn't the stdout already redirected to the file though via rsync? Maybe the > two can coincide. I wouldn't expect the --log-file option to redirect stdout. Even if it did, you can (and probably should) capture the rsync stderr via the pipe, and that should only close when the process exits. > Thanks Ken. This has been an enlightening discussion. You're welcome. Cheers, Ken _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
