Date: Wed, 31 Aug 2005 14:48:17 -0700 From: Gary Kline <kline@tao.thought.org> To: Dan Nelson <dnelson@allantgroup.com> Cc: Gary Kline <kline@tao.thought.org>, FreeBSD Mailing List <freebsd-questions@freebsd.org> Subject: Re: Doing a modulo in /bin/sh?? Message-ID: <20050831214817.GA60141@thought.org> In-Reply-To: <20050831184205.GC16354@dan.emsphone.com> References: <20050831181545.GA57907@thought.org> <20050831184205.GC16354@dan.emsphone.com>
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On Wed, Aug 31, 2005 at 01:42:05PM -0500, Dan Nelson wrote: > In the last episode (Aug 31), Gary Kline said: > > I can grab the results of "w=$date+%U)"; in C an use the modulo > > operator; is there a way to do this is /bin/sh? ot zsh? > > > > #/bin/sh > > w=$(date +%U) > > echo "w is $w"; > > (even=$(w % 2 )); ## flubs. > > echo "even is $even"; ## flubs. > > > > if [ $even -eq 0 ] ## flubs, obv'ly. > > then > > echo "week is even"; > > else > > echo "week is odd"; > > fi > > For the simple even/odd case, you can AND with 1: > > even=$(( w & 1 )) > > For the general case: > > xmodn=$(( x - ((x / n) * n) )) I didn't think of the first cast, but yep; the general is seriously sharp in my book; got to salt this away:-) Thanks. > > which works since sh's arithmetic evaluator is integer-only. > > zsh has the % modulo operator, so xmod=$(( x % n )) . > I knew ksh/zsh/bash(?) have it; forgot about `expr`, tho. gary -- Gary Kline kline@thought.org www.thought.org Public service Unix
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