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Re: [minor] "precision" of $SECONDS

From: Stephane Chazelas
Subject: Re: [minor] "precision" of $SECONDS
Date: Thu, 25 Feb 2016 17:20:16 +0000
User-agent: Mutt/1.5.21 (2010-09-15)

2016-02-25 10:48:51 -0500, Chet Ramey:
> Because bash doesn't have floating point arithmetic.

Yes, makes sense. mksh having $EPOCHREALTIME floating point even
though it doesn't have floating point arithmetic does sound

Any plan of adding floating point arithmetic support to bash by
the way?

> There's no
> real reason to have $SECONDS in a format you can't use to perform
> calculations.

That could be done with an extra $NANOSECONDS variable, but then
that wouldn't be reliable as in now=$SECONDS.$NANOSECONDS,
$SECONDS and $NANOSECONDS could be expanded at different seconds
(if run for instance at 00:00:00.9999999).

A printf '%(sec=%s nsec=%N)T' -1 wouldn't have the problem though.

> Bash's %T implementation doesn't have %N because it uses the libc
> strftime(3), and as far as I know, no strftime provides it.  I assume
> that ksh93 implements it internally as part of libast.

Probably. Note that GNU date also has a %N and doesn't use
strftime either. strftime taking a struct tm can't have
subseconds anyway.


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