Date: Wed, 3 Mar 2004 15:07:32 -0600 From: Dan Nelson <dnelson@allantgroup.com> To: Wayne Sierke <ws+freebsd-questions@au.dyndns.ws> Cc: freebsd-questions@freebsd.org Subject: Re: Size of variables in awk Message-ID: <20040303210731.GE79860@dan.emsphone.com> In-Reply-To: <1078334144.666.179.camel@ovirt.dyndns.ws> References: <1078286126.666.11.camel@ovirt.dyndns.ws> <20040303080359.GB79860@dan.emsphone.com> <1078304560.666.157.camel@ovirt.dyndns.ws> <20040303161840.GD79860@dan.emsphone.com> <1078334144.666.179.camel@ovirt.dyndns.ws>
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In the last episode (Mar 04), Wayne Sierke said:
> On Thu, 2004-03-04 at 02:48, Dan Nelson wrote:
> > In the last episode (Mar 03), Wayne Sierke said:
> > > I'm using the printf function in awk but something ain't right:
> > >
> > > # jot 4 30 | awk '{ printf("%u\n", 2^$1-1) }'
> > > 2147483648
> > >
> > > # jot 4 30 | awk '{ printf("%lu\n", 2^$1-1) }'
> > > 2147483648
> > >
> > > # jot 4 30 | awk '{ printf("%llu\n", 2^$1-1) }'
> > > 35186519572480
> >
> > I see nothing wrong here. %u is an unsigned int, and on x86 systems,
> > an int is 32 bits. %llu is a long long unsigned int, and they are 64
> > bits. Since there is no way for C to print a number larger than 64
> > bits, you won't be able to use the numeric specifiers to print large
> > numbers. You can use %s though. See
> > /usr/src/contrib/one-true-awk/run.c, the format() function.
>
> When you say "they are 64 bits" you're referring to a long
> (signed/unsigned) int (not long long unsigned int)?
>
> In which case aren't there two problems with the results shown?
>
> 1 - %u should print values up to 2^32-1
>
> 2 - %lu should print values up to 2^64-1
>
> whereas they're both hitting a limit at 2^31.
It's definitely weird. See run.c, line 865:
case 'o': case 'x': case 'X': case 'u':
flag = *(s-1) == 'l' ? 'd' : 'u';
break;
and line 897:
case 'd': sprintf(p, fmt, (long) getfval(x)); break;
case 'u': sprintf(p, fmt, (int) getfval(x)); break;
in which case I have no idea how the %llu output is working at all :)
--
Dan Nelson
dnelson@allantgroup.com
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