You can't guarantee that another process didn't happen to write a file with just that name, pid or not. Markus

-----Original Message----- From: Peter Simons [mailto:simons@cryp.to] Sent: Thursday, May 22, 2003 12:06 PM To: haskell-cafe@haskell.org Subject: Re: getpid() or something similar

Simon Marlow writes:

...

Even using a ProcessID doesn't guarnatee uniqueness [...]

Why not? If I use the file only temporarily (it is gone once the process terminates), something like /tmp/foo.<pid> will be unique, for all I can tell.

...

The right way to do this is to try to open it for writing, and try a different name if the open fails.

Unfortunately, this approach features a race condition because POSIX has no notion of mandatory file locking. I'd really rather avoid this, if I can.

Is there no other way? And one that works across different compilers?

Peter

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