Date: Thu, 25 Jun 2009 14:15:49 +0200 (CEST) From: Alexander Best <alexbestms@math.uni-muenster.de> To: Matthew Seaman <m.seaman@infracaninophile.co.uk> Cc: Wojciech Puchar <wojtek@wojtek.tensor.gdynia.pl>, Julian Elischer <julian@elischer.org>, freebsd-hackers@freebsd.org Subject: Re: small usr.bin/find patch Message-ID: <permail-200906251215491e86ffa800006660-a_best01@message-id.uni-muenster.de> In-Reply-To: <4A420073.6060405@infracaninophile.co.uk>
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wow. thanks a bunch for all the great info. Matthew Seaman schrieb am 2009-06-24: > Alexander Best wrote: > > hmmm...but dd e.g. uses lowercase instead of upercase letters to > > indicate > > kilobyte, megabyte and so on. isn't there some unix/posix/whatever > > standard > > telling app developers what to use? > Sure. The standard for scale-prefixes is defined by the Systeme > Internationale as part of the definition of SI units: > http://www.npl.co.uk/reference/measurement-units/si-prefixes/ > Note that these are strictly powers-of-10^3 multipliers, and > explicitly > not the computing style powers-of-2^10 commonly used for file sizes > or > hard drive capacities, which should instead use the somewhat clunky > Ki, > Mi, Gi etc. forms: > http://physics.nist.gov/cuu/Units/binary.html > These binary prefixes are mandated by the IEC and approved by the > IEEE > amongst others. > Not that many people use the binary prefixes appropriately, relying > on > context to disambiguate 1 MB = 1024 KB = 1,048,576 Bytes etc. Except > that (confusingly) as a measure of network bandwidth 10 Mb/s always > was > 10,000,000 b/s and never 10,485,760 b/s; a fact that has caught me > out > more than a few times. > Making find(1) / dd(1) / etc. operate pedantically correctly with > these > scale-factor symbols would cause a certain degree of pain for little > practical gain. Unless there was a broad consensus amongst all > Unixoid > OS providers, I can't see that change ever happening. > Cheers, > Matthew
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