printf ("%*c"... possible problem

[p5pRT]

Migrated from rt.perl.org#4556 (status was 'resolved')

Searchable as RT4556$

[p5pRT]

From [email protected]

Created by [email protected]

I believe there is a problem in the way perl handles field widths in
printf style format strings (especially w.r.t similar "C" handling).

perl -e 'printf ("%2c-\n", " ");'

should print out 2 spaces followed by a dash. ie. " -"

more simply​:

perl -e 'printf ("%c-\n", " ");'

does not print the space at all!

This also fails with perl 5.6.0 built for i586-linux.

Perl Info

Site configuration information for perl 5.00404:

Configured by fulko at Tue Aug 18 11:17:34 EDT 1998.

Summary of my perl5 (5.0 patchlevel 4 subversion 4) configuration:
  Platform:
    osname=sco_sv, osvers=3.2, archname=i386-sco_sv
    uname='sco_sv fulko 3.2 2 i386 '
    hint=previous, useposix=true, d_sigaction=define
    bincompat3=y useperlio=undef d_sfio=undef
  Compiler:
    cc='cc', optimize=' ', gccversion=
    cppflags='-w0 -U M_XENIX -DPERL_SCO5 -I/usr/local/include'
    ccflags ='-w0 -U M_XENIX -DPERL_SCO5 -I/usr/local/include'
    stdchar='unsigned char', d_stdstdio=undef, usevfork=false
    voidflags=15, castflags=0, d_casti32=undef, d_castneg=define
    intsize=4, alignbytes=4, usemymalloc=y, prototype=define
  Linker and Libraries:
    ld='ld', ldflags =' -L/usr/local/lib'
    libpth=/usr/local/lib /shlib /lib /usr/lib /usr/ccs/lib
    libs=-lintl -lsocket -lnsl -lndbm -ldbm -lld -lm -lc -lcrypt -lPW -lx
    libc=, so=so
    useshrplib=false, libperl=libperl.a
  Dynamic Linking:
    dlsrc=dl_none.xs, dlext=none, d_dlsymun=undef, ccdlflags=''
    cccdlflags='', lddlflags=''

Locally applied patches:
	


@INC for perl 5.00404:
	/usr/local/lib/perl5/i386-sco_sv/5.00404
	/usr/local/lib/perl5
	/usr/local/lib/perl5/site_perl/i386-sco_sv
	/usr/local/lib/perl5/site_perl
	.


Environment for perl 5.00404:
    HOME=/u/fulko
    LANG=C_C.C
    LD_LIBRARY_PATH=/usr/lib:/lib:/usr/local/lib:/usr/ccs/lib:/usr/progrerssive/lib:/usr/skunk/lib
    LOGDIR (unset)
    PATH=/u/local/bin:/bin:/usr/bin:/usr/dbin:/usr/ldbin:/usr/bin/X11:/u/snap7.0/bin:/usr/java/bin:.
    PERL_BADLANG (unset)
    SHELL=/bin/ksh

[p5pRT]

From [Unknown Contact. See original ticket]

On Oct 31, fulko@​wecan.com said​:

perl -e 'printf ("%2c-\n", " ");'

You're used to the C idiom of​:

  printf("%2c-", ' ');

where ' ' is not an actual space, but rather the number 32. The %c format
takes an integer, and converts it to the corresponding character.

perl -e 'printf ("%c-\n", " ");'

  jeffp@​friday [9​:27am] ~ #190> perl -lwe 'printf "<%c>", " "'
  Argument " " isn't numeric in prtf at -e line 1.
  jeffp@​friday [9​:27am] ~ #191> perl -lwe 'printf "<%c>", ord(" ")'
  < >

Why did Perl abbreviate 'printf' as 'prtf'?

[p5pRT]

From @vanstyn

In <10010310919.aa08664@​wecan.com>, fulko@​wecan.com writes​:
:
:I believe there is a problem in the way perl handles field widths in
:printf style format strings (especially w.r.t similar "C" handling).
:
:perl -e 'printf ("%2c-\n", " ");'
:
:should print out 2 spaces followed by a dash. ie. " -"

No, it should format chr(" ") in a two character field. Now chr(" ") is
the same as chr(0), and perl does indeed print a space followed by a
zero byte followed by a dash.

If you turn on warnings, you will be given a clue to this​:
  Argument " " isn't numeric in printf at -e line 1.

You can also verify that the zero byte is printed by piping the output
to od(1) or similar.

Hope this helps,

Hugo

[p5pRT]

From @JohnPeacock

Even stranger is why his code prints "fine" under NT​:

  D​:\>perl -we "printf ("""-%2c-\n""", """ """);"
  Argument " " isn't numeric in printf at -e line 1.
  - -

  D​:\>

John Peacock

Jeff Pinyan wrote​:

Why did Perl abbreviate 'printf' as 'prtf'?

--
Jeff "japhy" Pinyan japhy@​pobox.com http​://www.pobox.com/~japhy/
PerlMonth - An Online Perl Magazine http​://www.perlmonth.com/
The Perl Archive - Articles, Forums, etc. http​://www.perlarchive.com/
CPAN - #1 Perl Resource (my id​: PINYAN) http​://search.cpan.org/

[p5pRT]

From [Unknown Contact. See original ticket]

Behind-the-scenes mail between John Peacock and myself
has confirmed that NT, too, is printing a blank and a byte of 0's,
which NT saw fit to display as two blanks.

That leaves the somewhat odd difference in the opcode.h tables,
UNIX with "prtf", NT with "printf". -- jpl

[p5pRT]

From @jhi

On Tue, Oct 31, 2000 at 09​:29​:22AM -0500, Jeff Pinyan wrote​:

On Oct 31, fulko@​wecan.com said​:

perl -e 'printf ("%2c-\n", " ");'

You're used to the C idiom of​:

printf("%2c-", ' ');

where ' ' is not an actual space, but rather the number 32. The %c format
takes an integer, and converts it to the corresponding character.

perl -e 'printf ("%c-\n", " ");'

jeffp@​friday [9​:27am] ~ #190> perl -lwe 'printf "<%c>", " "'
Argument " " isn't numeric in prtf at -e line 1.
jeffp@​friday [9​:27am] ~ #191> perl -lwe 'printf "<%c>", ord(" ")'
< >

Why did Perl abbreviate 'printf' as 'prtf'?

Perl 5.6.0​:

$ perl -lwe 'printf "<%c>", " "'
Argument " " isn't numeric in printf at -e line 1.

[p5pRT]

From @jhi

On Tue, Oct 31, 2000 at 10​:53​:59AM -0500, John P. Linderman wrote​:

Behind-the-scenes mail between John Peacock and myself
has confirmed that NT, too, is printing a blank and a byte of 0's,
which NT saw fit to display as two blanks.

That leaves the somewhat odd difference in the opcode.h tables,
UNIX with "prtf", NT with "printf". -- jpl

Which version of Perl on UNIX does this? As I noted at least 5.6.0
should have it right.

[p5pRT]

From [Unknown Contact. See original ticket]

On Tue, Oct 31, 2000 at 10​:53​:59AM -0500, John P. Linderman wrote​:

Behind-the-scenes mail between John Peacock and myself
has confirmed that NT, too, is printing a blank and a byte of 0's,
which NT saw fit to display as two blanks.

That leaves the somewhat odd difference in the opcode.h tables,
UNIX with "prtf", NT with "printf". -- jpl

Which version of Perl on UNIX does this? As I noted at least 5.6.0
should have it right.

--
$jhi++; # http​://www.iki.fi/jhi/
# There is this special biologist word we use for 'stable'.
# It is 'dead'. -- Jack Cohen

This is perl, version 5.005_03 built for sgi6-irix

The curse of having too many versions of Perl on too many hosts,
many of which are not under my control. I cut-and-pasted the
original test code into the nearest window, and happened across
a ``bad'' one. Indeed, opcode.h is fine under 5.6 and 5.7.
Sorry -- jpl