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List:       kde-devel
Subject:    RE: Single instance only applications
From:       "Glen Parker" <glenebob () nwlink ! com>
Date:       1999-07-29 21:06:28
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> Well, if you insist to use lock files, you can just write some text into
> the file so that such multi-instance programs can check and decide if
> they're allowed to run another instance exactly because another option is
> used. E.g., writing "screensaver" in the lock file, will allow kcmdisplay
> to spawn a new process if you attempt to run `kcmdisplay color` but not if
> you try to start `kcmdisplay screensaver`. But, once again, lock files

But really, this should be done in the file name, like:
kcmdisplay.$DISPLAY.<OPTION_ENCODING>.lock
And maybe write the pid into the file.
That way, a second instance would generate a file name, and if it already
exists, then exit, without having to worry about the contents (except for
error reporting maybe).

> are a poor solution: a) because user can change them (their name,
> delete them, or change their contents) b) and what you can do if you have

So?  A user should be expected to live with the consequenses of modifying
files in /tmp.  Besides, no ordinary user would do that anyway.

> `kcmdisplay screensaver` running and user tries to run `kcmdisplay` (with
> all tabs). Then you certainly want to have `kcmdisplay` running, but
> you'll have the screensaver functions duplicated (which is wrong, I
> agree).

 --
Glen Parker
glenebob@nwlink.com

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