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Re: Number with sign is read as octal despite a leading 10#


From: Ilkka Virta
Subject: Re: Number with sign is read as octal despite a leading 10#
Date: Tue, 10 Jul 2018 21:41:56 +0300
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:52.0) Gecko/20100101 Thunderbird/52.9.0

On 10.7. 18:09, Chet Ramey wrote:
On 7/10/18 6:44 AM, Ilkka Virta wrote:
I think the problematic case here is when the number comes as input from
some program, which might or might not print a leading sign or leading
zeroes, but when we know that the number is, in any case, decimal.

E.g. 'date' prints leading zeroes, which is easy enough to handle:

hour=$(date +%H)

hour=${hour#0}         # remove one leading zero, or
hour="10#$hour"        # make it base-10

The latter works even with more than one leading zero, but neither works
with a sign. So, handling numbers like '-00159' gets a bit annoying:

That is not an integer constant. Integer constants don't begin with `-'.
Bash uses the same definition for constants as the C standard, with the
addition of the `base#value' syntax.

At least from my point of view this isn't necessarily a bug, more like a feature request. The behaviour matches the description you just wrote, and also the documentation. That doesn't mean it's the only possible behaviour.

Changing the parsing here could be useful, and would improve compatibility with ksh and zsh. I don't think there's any alternative sensible meaning for 10#-0123 anyway, but I might be mistaken.

Since the `10#' notation is sufficient to deal with leading zeroes if you
want to force decimal, you only have to remove a leading unary plus or
minus.

Which I thought I just did, and Pierre provided a better way to do it (thanks).

Not having to splice the sign around would make this somewhat easier though, but YMMV.

--
Ilkka Virta / address@hidden



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