Messages in this thread | | | Date | Fri, 15 Feb 2008 14:25:55 -0500 | From | Bill Davidsen <> | Subject | Re: Is there a "blackhole" /dev/null directory? |
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Jan Engelhardt wrote: > On Feb 14 2008 10:46, Andi Kleen wrote: >> Jasper Bryant-Greene <jasper@unix.geek.nz> writes: >>> This could be done fairly trivially with FUSE, and IMHO is a good use >>> for FUSE because since you're just throwing most data away, performance >>> is not a concern. > > There is a much more interesting 'problem' with a "/dev/null directory". > > Q: Why would you need such a directory? > A: To temporarily fool a program into believing it wrote something.
Also: to let a program believe it was creating files which are used to hold the written data. Otherwise /dev/null would probably be the solution. > > Q: Should all files disappear? (e.g. "unlink after open") > A: Maybe not, programs may stat() the file right afterwards and > get confused by the "inexistence".
I think what is going to happen is that files created behave as if they are the result of a mknod resulting in a /dev/null clone. > > Q: What if a program attempts to mkdir /dev/nullmnt/foo to just > create a file /dev/nullmnt/foo/barfile? > A: /dev/nullmnt/foo must continue to exist or be accepted for a while, > or perhaps for eternity.
The directory structure can persist, it's the writing of data which can be avoided.
Real example:
A program which reads log files and prepares a whole raft of reports in a directory specified. If you just want to see the summary (stdout) and exception notices (stderr) having a nulldir would avoid the disk space and i/o load if you were just looking at the critical output rather than the analysis.
Yes, if this was an original program requirement it would or should have been a feature. Real world cases sometimes use tools in creative ways.
-- Bill Davidsen <davidsen@tmr.com> "We have more to fear from the bungling of the incompetent than from the machinations of the wicked." - from Slashdot
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