From owner-freebsd-questions  Sun Feb 25 14:48:23 2001
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Date: Sun, 25 Feb 2001 14:48:21 -0800 (PST)
From: Marc W <mwlist@lanfear.com>
Message-Id: <200102252248.OAA36102@akira.lanfear.com>
To: freebsd-questions@freebsd.org
Subject: Getting around a broken O_EXCL
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hello!

    i want to set up a named pipe (FIFO) to prevent multiple instances
of a program i'm writing.   what i wanted to have the programs do is:

    -- check for FIFO
    -- if !FIFO,   int res = mkfifo("unique fifo name", O_EXCL);
    if (res == -1 && errno ==  EWOULDBLOCK)  recheck for FIFO
    else if (res == -1) abort or something
    else spawn thread and wait on FIFO.

    now, the problem is that, in reading the Linux docs, O_EXCL appears
to be busted on NFS, and I'm assuming on other OSes, including FreeBSD
as well.

    So, what are my options to get around this?  i'd really rather
there not be a potential race condition in my program.

    marc.




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