Re: [gtk-list] Re: Detecting multiple application instances

[Andrew Wood <ivarch cus umist ac uk>]

My first thought was to use IPC - isn't there some way of testing to see if
another program already holds a particular resource? Don't know enough about
IPC to be sure (never used it myself) but presumably it would mean that you
could open the same application on 2 machines sharing the same home
directory, which Netscape would (I imagine) break on due to the file already
existing.

Looking at the ipc(5) man page it looks like IPC_CREAT | IPC_EXCL could be
used as a sort of machine-specific "lock file". You could also use IPC to
cause the second, unwanted, process to message the first and tell it to open
a new window.

Just my 2p. ;)

- Andrew


On Thu, 19 Aug 1999, Daniel Solaz wrote:

> Use a lock file somewhere in the users home directory.  Put the PID
> inside so other instances can check with kill() whether the lock is held
> by an existing process or has been left behind.  Check the lock at the
> beginning of your program: open() can be used to atomically
> test-or-create the lock file.  Destroy the lock you hold at exit.
> This is what netscape's communicator does.  I've done it in some
> programs and works fine.  I can email some code if you want.
> -Daniel