From: Daniel Shahaf <d.s@daniel.shahaf.name>
To: TJ Luoma <luomat@gmail.com>
Cc: Zsh-Users List <zsh-users@zsh.org>
Subject: Re: Converting bash script to zsh for converting bytes to 'readable'
Date: Wed, 12 Sep 2018 23:08:42 +0000 [thread overview]
Message-ID: <20180912230842.db66mgh3px2rsbru@tarpaulin.shahaf.local2> (raw)
In-Reply-To: <20180912230445.fpfihe7htuqkfbed@tarpaulin.shahaf.local2>
Daniel Shahaf wrote on Wed, Sep 12, 2018 at 23:04:45 +0000:
> 1 zmodload zsh/mathfunc
> 2 f() {
> 3 setopt localoptions ksharrays
> 4 integer i=$(( log2( $1 )/10 ))
> 5 local -a SI=( '' 'Ki' 'Mi' 'Gi' )
> 6 printf '%5.2g %s\n' "$(( ($1)*1.0 / (1<<(10*i)) ))" "${SI[i]}B"
> 7 }
A subtle point here: in an arithmetic expression, using raw variable names
behave as one'd expect, but using variable expansions does not. Compare:
% s='1+1'
% echo $(( s * 2 ))
4
% echo $(( $s * 2 ))
3
%
That's why I put parentheses around the «$1» in the math expression: that
ensures consistent parsing even if $1 is an expression (as in «f "1024+1024"»).
Cheers,
Daniel
(It's exactly the same issue as with C macros)
prev parent reply other threads:[~2018-09-12 23:09 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-12 22:02 TJ Luoma
2018-09-12 22:38 ` TJ Luoma
2018-09-12 22:52 ` Bart Schaefer
2018-09-12 23:04 ` Daniel Shahaf
2018-09-12 23:08 ` Daniel Shahaf [this message]
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