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[Mike Tremell] "/dev/null and /dev/zero on Linux and Unix: What's the difference?"
http://linuxshellaccount.blogspot.com/2009/04/devnull-and-devzero-on-linux-and-unix.html
(via http://www.digg.com/linux_unix/)
読むこと ← 自分 (digg の コメント欄も チェック)。
(追記)
/dev/zero returns numbers, /dev/null doesn't return anything.
If you go 'dd if=/dev/zero of=test bs=512 count=1' you'll get a file containing 512 bytes of zero, if you go 'dd if=/dev/null of=test bs=512 count=1' you'll get a file containg 0 bytes.
Simple, assuming I've remembered this right.
(from comments of dig readers)