Date: Wed, 21 Apr 2010 00:50:03 GMT From: Garrett Cooper <yanegomi@gmail.com> To: freebsd-bugs@FreeBSD.org Subject: Re: bin/145748: hexdump(1) %s format qualifier broken Message-ID: <201004210050.o3L0o36p068229@freefall.freebsd.org>
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The following reply was made to PR bin/145748; it has been noted by GNATS.
From: Garrett Cooper <yanegomi@gmail.com>
To: Wayne Sierke <ws@au.dyndns.ws>
Cc: bug-followup@freebsd.org
Subject: Re: bin/145748: hexdump(1) %s format qualifier broken
Date: Tue, 20 Apr 2010 17:49:43 -0700
On Tue, Apr 20, 2010 at 7:33 AM, Wayne Sierke <ws@au.dyndns.ws> wrote:
>> The fact that "%4s" fails and isn't noted in the addendum is a failure
>> according to the specifications of hexdump as per the manpage; "%.4s"
>> passing is a reasonable workaround for broken "%[:digit:]s"
>> functionality.
>
> I should have made my earlier reply more explicit. It doesn't seem to be
> a failure.
The issue with %4s failing is still a failure. The non-issue with
%.4s, %0.4s etc not failing is not a failure; it's just a bit more
obfuscated logic.
> The part of the hexdump(1) manpage quoted previously:
>
> o A byte count or field precision is required for each ``s'' con-
> version character (unlike the fprintf(3) default which prints
> the entire string if the precision is unspecified).
That statement is misleading. It should make the above statement with
field width, not [field] precision. FWIW, the statement `field
precision' makes absolutely no sense in the terminology used by
printf(3), and is most likely a typo.
And finally, yes I agree that %s is illegal because you can't qualify
the number of characters required for each format unit -- something
that's required for hexdump to function. %4s, etc with precision not
being specified is legal however.
> And as observed hexdump does accept the required value when passed a
> "field precision" - the numeric value immediately after the period in
> "%.4s" (NB not a "field width" - as described in fprintf(3) and slightly
> more clearly in printf(3)).
From printf(3):
o An optional decimal digit string specifying a minimum field width.
If the converted value has fewer characters than the field width, it
will be padded with spaces on the left (or right, if the left-adjust-
ment flag has been given) to fill out the field width.
o An optional precision, in the form of a period . followed by an
optional digit string. If the digit string is omitted, the precision
is taken as zero. This gives the minimum number of digits to appear
for d, i, o, u, x, and X conversions, the number of digits to appear
after the decimal-point for a, A, e, E, f, and F conversions, the
maximum number of significant digits for g and G conversions, or the
maximum number of characters to be printed from a string for s con-
versions.
Note the word `optional' in the first and second clauses. `.' isn't
required except to disambiguate precision from field width.
Thanks,
-Garrett
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