Re: [Help-bash] About printf "%d\n" with no arguments.

[Dan Douglas]

On Tuesday, July 16, 2013 08:34:00 PM Eric Blake wrote:
> On 07/16/2013 08:04 PM, Peng Yu wrote:
> > Hi,
> > 
> > The following command will print "0". But I think the appropriate
> > output should be nothing. As mentioned in the man page "Write  the
> > formatted  arguments  to the standard output under the control of the
> > format", since there are no arguments, nothing should be printed. Is
> > there a way to configure printf to do what I just described? Thanks.
> > 
> > ~$ printf "%d\n"
> > 0
> 
> POSIX requires this behavior:
> http://pubs.opengroup.org/onlinepubs/9699919799/utilities/printf.html
> "9. The format operand shall be reused as often as necessary to satisfy
> the argument operands. Any extra c or s conversion specifiers shall be
> evaluated as if a null string argument were supplied; other extra
> conversion specifications shall be evaluated as if a zero argument were
> supplied. If the format operand contains no conversion specifications
> and argument operands are present, the results are unspecified."
> 
> And ksh and dash agree.  Sorry, but even if this behavior is not what
> you desire, it is intentional in order to comply with POSIX.
> 

It might be noted that there are exceptions in non-POSIX extensions. Bash 4.3 
and ksh give a non-empty implicit value to '%()T' arguments, and ksh93 and zsh 
(and mksh's corresponding feature) omit the implicit null argument for '%q', 
which as I've mentioned previously is probably the better behavior.

-- 
Dan Douglas