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    No, with lockrun you don't have a problem - when a NFS server hangs, all lockrun calls will hang (at least) in the lockf() system call - when it is back up all processes are resumed but only one process will win the lock. No race condition. I don't run into such problems with cronjobs a lot - the opposite is the case - but this is a problem when it hits you it has the potential to create a lot of pain. Commented Oct 4, 2011 at 20:15
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    I have accepted this answer because the method is safe and so far the most elegant one. I suggest a small variant: set -o noclobber && echo "$$" > "$lockfile" to get a safe fallback when the shell does not support the noclobber option. Commented Oct 7, 2011 at 9:45
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    Good answer, but you should also 'kill -0' the value in lockfile to ensure that the process that created the lock still exists. Commented Dec 17, 2014 at 13:29
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    The noclobber option may be prone to race conditions. See mywiki.wooledge.org/BashFAQ/045 for some food for thought. Commented Jun 16, 2015 at 5:09
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    Note: using noclobber (or -C) in ksh88 does not work because ksh88 does not use O_EXCL for noclobber. If you're running with a newer shell you may be OK... Commented Nov 17, 2015 at 19:24