levy@ucbvax.Berkeley.EDU@ttrdc.UUCP (12/04/86)
I have found what appears to be a bug in printf under VMS C 2.0 (running on
VMS 4.3).
main()
{
printf("X%2.2dX\n",2);
}
will produce the output line
X 2X
^
|
+-[this is a blank]
when compiled in the aforementioned VMS C.
Under all versions of UNIX C compilers that I have tried, I get what I want:
X02X
Is this a "known bug"? Is there some workaround which doesn't require using
different format strings depending on the value of the number being printed?
(I want to print numbers in the range 0-99 and have them come out as precisely
two digits. And I want to do it portably in C.) THANKS....
--
------------------------------- Disclaimer: The views contained herein are
| dan levy | yvel nad | my own and are not at all those of my em-
| an engihacker @ | ployer or the administrator of any computer
| at&t computer systems division | upon which I may hack.
| skokie, illinois |
-------------------------------- Path: ..!{akgua,homxb,ihnp4,ltuxa,mvuxa,
go for it! allegra,ulysses,vax135}!ttrdc!levycarl@CITHEX.CALTECH.EDU.UUCP (12/07/86)
Use
printf("X%02.2dX\n", 2);
instead of
printf("X%2.2dX\n", 2);bzs@BU-CS.BU.EDU.UUCP (12/07/86)
From: levy@ucbvax.Berkeley.EDU@ttrdc.UUCP >I have found what appears to be a bug in printf under VMS C 2.0 (running on >VMS 4.3). > >main() >{ > > printf("X%2.2dX\n",2); >} > >will produce the output line >X 2X > ^ > | > +-[this is a blank] > >when compiled in the aforementioned VMS C. > >Under all versions of UNIX C compilers that I have tried, I get what I want: >X02X Use: printf("X%02.2dX\n",2); ^ (this works on UNIX also and is "more correct", I'm not sure that what you were relying upon didn't work by accident, see the printf man page.) -Barry Shein, Boston University
campbell@maynard.UUCP.UUCP (12/07/86)
In article <8612041854.AA23322@ucbvax.Berkeley.EDU> levy@ucbvax.Berkeley.EDU@ttrdc.UUCP writes: >I have found what appears to be a bug in printf under VMS C 2.0 (running on >VMS 4.3). >... > printf("X%2.2dX\n",2); > >will produce the output line >X 2X > ... >Under all versions of UNIX C compilers that I have tried, I get what I want: >X02X > >Is this a "known bug"? Yes, it is a "known bug" in your program. You want: printf("X%02dX\n",2); I tried your example under VENIX (UNIX V7) and got "X 2X", as I should. See K&R, page 146. In fact, if the UNIX C compilers you tried really produced "X02X", they disagree with K&R, and should be fixed. -- Larry Campbell The Boston Software Works, Inc. Internet: campbell@maynard.bsw.com 120 Fulton Street, Boston MA 02109 uucp: {alliant,wjh12}!maynard!campbell +1 617 367 6846 ARPA: campbell%maynard.uucp@harvisr.harvard.edu MCI: LCAMPBELL
mic@NGP.UTEXAS.EDU (Mic Kaczmarczik) (12/09/86)
In article <8612041854.AA23322@ucbvax.Berkeley.EDU> levy@ucbvax.Berkeley.EDU@ttrdc.UUCP writes: >I have found what appears to be a bug in printf under VMS C 2.0 (running on >VMS 4.3). > >main() >{ > > printf("X%2.2dX\n",2); >} > >will produce the output line >X 2X > ^ > | > +-[this is a blank] > >when compiled in the aforementioned VMS C. > >Under all versions of UNIX C compilers that I have tried, I get what I want: >X02X > >Is this a "known bug"? Is there some workaround which doesn't require using >different format strings depending on the value of the number being printed? >(I want to print numbers in the range 0-99 and have them come out as precisely >two digits. And I want to do it portably in C.) THANKS.... >-- > ------------------------------- Disclaimer: The views contained herein are >| dan levy | yvel nad | my own and are not at all those of my em- >| an engihacker @ | ployer or the administrator of any computer >| at&t computer systems division | upon which I may hack. >| skokie, illinois | > -------------------------------- Path: ..!{akgua,homxb,ihnp4,ltuxa,mvuxa, > go for it! allegra,ulysses,vax135}!ttrdc!levy Try printf("X%02dX\n",2); This should do exactly what you said you wanted: print 2-digit numbers, padded on the left with 0's. (Of course, that's only as long as the numbers are between 0 and 99. If the number is 100, the number will use three spaces anyway.) Now, is the way VAX C interprets the format string "%2.2d" a bug? If it don't work like Unix, it's probably a bug :-)... However, the Berkeley 4.3 printf() man page indicates the first 2 is a "field width", basically meaning the %d conversion should output *at least* that many spaces. The 2 after the period is the "precision", meaning the *maximum* number of spaces the field should use. Going by this, I wouldn't have expected the output to be zero-padded (if I use a precision on a string, do I want it zero-padded?), but perhaps it makes sense in some situations to have %2.2d work that way. Any C wizards care to comment? Mic Kaczmarczik User Services Digital Support Group UT Austin Computation Center ...!ihnp4!seismo!ut-sally!ut-ngp!mic mic@ngp.utexas.edu ccep001@UTADNX.BITNET
LEICHTER-JERRY@YALE.ARPA.UUCP (12/10/86)
Reply-To: <LEICHTER-JERRY@YALE.ARPA>
... [U]nder VMS C 2.0 (running on VMS 4.3)
main()
{ printf("X%2.2dX\n",2); }
will produce the output line
X 2X
^
+-[this is a blank]
...Under all versions of UNIX C compilers that I have tried, I get what I
want: X02X Is this a "known bug"? Is there some workaround which
doesn't require using different format strings depending on the value of
the number being printed? (I want to print numbers in the range 0-99 and
have them come out as precisely two digits. And I want to do it portably
in C.)
Assuming you are reporting accurately the format string you are using, and
the output you are getting, you have indeed discovered a bug - in "all ver-
sions of UNIX C compilers that [you] have tried"! The documentation of printf
is quite clear: Fields are right-justified with SPACES, not 0's. You can
request zero fill by preceeding the field width with a 0, as in:
printf("X%02.2dX\n",2);
-- Jerry
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