launching on Wintel/inter-process communication

[Richard Gaskin]

Yennie at aol.com wrote:

> Simple. Write the milliseconds into the file. Then, when the app launches,
> grab the milliseconds as its "launch date". When it goes to look in the
> folder, it will read in the "leftover" file, but because the milliseconds in
> the leftover is *earlier* than the launch date, it is ignored. It will only
> read files written into the "watched" folder *after* the launch date.
> 
> The time stamp seems logical- but here's my question: how does a second
> instance of the application know what file to look for? That is, if the file
> is already there from the first instance which was launched hours ago, how can
> it tell the difference between that file and a crashed one.

That's where the time stamp comes in.

In the event that a crash occurs before any time limit had been exceeded,
then yes, the app could become confused and refuse to run.  So you get a
tech support call and tell them to hold a modifier on launch to clear that
out.  It's probably fewer support calls than you'll get for alternatives
like always quitting the first instance or having two instances open (two
instances is not bad for the single-window model, but for the project model
like Rev uses it's not optimal).

-- 
 Richard Gaskin 
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