Date: Fri, 12 Aug 2005 10:54:49 +0800 From: Xu Qiang <Qiang.Xu@fujixerox.com> To: dpk <dpk@dpk.net>, Xu Qiang <Qiang.Xu@fujixerox.com> Cc: freebsd-questions@freebsd.org Subject: RE: Help on bash script? Message-ID: <20050812025115.CB2561D93C@imss.sgp.fujixerox.com>
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dpk wrote: > On Fri, 12 Aug 2005, Xu Qiang wrote: >> 1. The way of incrementing the variable NCOREFILES. Why does it use >> the formula of "NCOREFILES=3D$[ $NCOREFILES + 1 ]", and not the direct >> way of "NCOREFILES=3D$NCOREFILES+1"? > = > If that was done, NCOREFILES would end up looking like: > = > +1+1+1+1+1+1+1 > = > as bash does not automatically differentiate between numeric and > string variables. What the funky looking construct does is convince > bash to treat it as a numeric/arithmetic expression. Strangely, there is no mention of this assignment usage in the book "Learni= ng the bash shell, 2nd ed" by O'Reilly at my hand. :( And "man bash" didn't talk of it either. However, it mentioned for arithmet= ic evaluation, we can use = id++ id-- variable post-increment and post-decrement ++id --id variable pre-increment and pre-decrement If it is correct, then I can also increment NCOREFILES by: = ++NCOREFILES. = But I doubt it... Regards, Xu Qiang
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