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/dev/null And /dev/zero On Linux And Unix: What's The Difference?

Apr 29, 2009, 20:02 (0 Talkback[s])
(Other stories by Mike Tremell)

[ Thanks to Mike Golvach for this link. ]

"2. Reading from /dev/null and /dev/zero: This is where the difference between the two files becomes apparent. The most significant difference is exposed in the "reading" since this action highlights the major way in which the two differ.

"/dev/null is, essentially, a black hole. Writes to it (as noted above), basically go down the drain. They go nowhere, stay there and you can't get them back. When you "read" from /dev/null, the same rule holds true. /dev/null is virtually "nothing," and all reads from it produce no output whatsoever. For instance, this output from Solaris' truss (you can get the same from Linux's "strace" and similar utilities) shows what happens when /dev/null is read from (e.g. "cat /dev/null") - below, what you'd see at the command line, followed by a snippet of truss output from the almost-immediate end of the command's execution:"

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