Re: sprintf and the trailing null

From	jt@toerring.de (Jens Thoms Toerring)
Newsgroups	comp.lang.c
Subject	Re: sprintf and the trailing null
Date	2015-07-06 14:15 +0000
Organization	Freie Universitaet Berlin
Message-ID	<cvvgsmFudv8U1@mid.uni-berlin.de> (permalink)
References	<be51c03d-a8d6-4c66-b490-85466818284d@googlegroups.com> <mndvt7$299$1@dont-email.me> <4218c1d7-073c-48a4-8485-687a794848d1@googlegroups.com>

Show all headers | View raw

Rick C. Hodgin <rick.c.hodgin@gmail.com> wrote:
> On Monday, July 6, 2015 at 9:31:49 AM UTC-4, John McCue wrote:
> > Rick C. Hodgin <rick.c.hodgin@gmail.com> wrote:
> > > Two questions:
> > >  (1) Is there a version of sprintf() without a trailing NULL?
> > I have not seen any, but what are you trying to accomplish ?

> One example:

>     char buffer[8];
>     sprintf(buffer, "%04u%02%02u", year, month, day);

> > >  (2) Why does sprintf() automatically insert a trailing NULL?
> > 
> > You can see why if you replace the 'trailing NULL' with another
> > character and print out the string.

> Why not options:

>     sprintf0(buffer, "%04u", value);    // NULL-terminated form
>     sprintf(buffer, "%04u\0", value);   // Manually terminated (if needed)

As someone else already pinted out, you'd need a something
different for the "don't output a trailing '\0'" marker...

> Or at this point in support of legacy systems, a new function:
>     rawprintf(buffer, "%04u\0", value); // No NULL-termination by default

because the 's' at the start of sprintf() stands for "string"
and strings are strings because the have a'\0' at the end -
otherwise it would be just a char array.

What would be an sprintf() variant be useful that doens't write
a trailing '\0'? The only reason I can think of is that you want
to write to some memory location of restricted size and the trai-
ling '\0' is one too much. But in that case you can use snprintf()
to ensure that no more that the number of chars you want get out-
put, i.e. in your example

    snprint( buffer, 4, "%04u\n", value );

would probably do the trick (this, of course, assumes that 'value'
never is larger than 9999).
                                 Regards, Jens
-- 
  \   Jens Thoms Toerring  ___      jt@toerring.de
   \__________________________      http://toerring.de

Thread

sprintf and the trailing null "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-07-06 06:16 -0700
  Re: sprintf and the trailing null John McCue <jmccue@jmcnet1.bstnma.east.verizon.net> - 2015-07-06 13:30 +0000
    Re: sprintf and the trailing null "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-07-06 06:37 -0700
      Re: sprintf and the trailing null Reinhardt Behm <rbehm@hushmail.com> - 2015-07-06 21:58 +0800
        Re: sprintf and the trailing null "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-07-06 07:12 -0700
          Re: sprintf and the trailing null Reinhardt Behm <rbehm@hushmail.com> - 2015-07-06 22:34 +0800
            Re: sprintf and the trailing null "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-07-06 08:44 -0700
          Re: sprintf and the trailing null Bartc <bc@freeuk.com> - 2015-07-06 15:46 +0100
            Re: sprintf and the trailing null Keith Thompson <kst-u@mib.org> - 2015-07-06 08:06 -0700
              Re: sprintf and the trailing null Bartc <bc@freeuk.com> - 2015-07-06 17:42 +0100
                Re: sprintf and the trailing null "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-07-06 09:48 -0700
                Re: sprintf and the trailing null Bartc <bc@freeuk.com> - 2015-07-06 18:07 +0100
                Re: sprintf and the trailing null Martin Shobe <martin.shobe@yahoo.com> - 2015-07-06 12:40 -0500
                Re: sprintf and the trailing null Keith Thompson <kst-u@mib.org> - 2015-07-06 10:46 -0700
                Re: sprintf and the trailing null Bartc <bc@freeuk.com> - 2015-07-06 18:58 +0100
          Re: sprintf and the trailing null Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-07-06 16:38 +0100
            Re: sprintf and the trailing null Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-07-06 23:44 +0100
              Re: sprintf and the trailing null "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-07-06 15:48 -0700
              Re: sprintf and the trailing null Phil Carmody <pc+usenet@asdf.org> - 2015-07-08 20:09 +0300
                Re: sprintf and the trailing null "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-07-08 10:11 -0700
                Re: sprintf and the trailing null Bartc <bc@freeuk.com> - 2015-07-08 19:01 +0100
                Re: sprintf and the trailing null David Kleinecke <dkleinecke@gmail.com> - 2015-07-09 09:02 -0700
                Re: sprintf and the trailing null Richard Heathfield <rjh@cpax.org.uk> - 2015-07-09 17:07 +0100
                Re: sprintf and the trailing null Phil Carmody <pc+usenet@asdf.org> - 2015-07-10 17:06 +0300
                Re: sprintf and the trailing null glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-07-09 17:42 +0000
                Re: sprintf and the trailing null Phil Carmody <pc+usenet@asdf.org> - 2015-07-10 13:33 +0300
                Re: sprintf and the trailing null Bartc <bc@freeuk.com> - 2015-07-10 12:09 +0100
                Re: sprintf and the trailing null Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-07-10 04:51 -0700
                Re: sprintf and the trailing null Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-07-10 17:24 +0100
                Re: sprintf and the trailing null Keith Thompson <kst-u@mib.org> - 2015-07-10 08:33 -0700
                Re: sprintf and the trailing null Tim Rentsch <txr@alumni.caltech.edu> - 2015-07-11 04:58 -0700
      Re: sprintf and the trailing null jt@toerring.de (Jens Thoms Toerring) - 2015-07-06 14:15 +0000
        Re: sprintf and the trailing null "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-07-06 07:20 -0700
          Re: sprintf and the trailing null raltbos@xs4all.nl (Richard Bos) - 2015-07-06 19:54 +0000
            Re: sprintf and the trailing null "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-07-06 13:31 -0700
              Re: sprintf and the trailing null Richard Heathfield <rjh@cpax.org.uk> - 2015-07-06 21:52 +0100
              Re: sprintf and the trailing null raltbos@xs4all.nl (Richard Bos) - 2015-07-06 22:52 +0000
                Re: sprintf and the trailing null Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-07-07 01:04 +0100
                Re: sprintf and the trailing null Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-07-06 19:13 -0700
                Re: sprintf and the trailing null Reinhardt Behm <rbehm@hushmail.com> - 2015-07-07 12:45 +0800
                Re: sprintf and the trailing null Rosario19 <Ros@invalid.invalid> - 2015-07-07 10:15 +0200
                Re: sprintf and the trailing null Bartc <bc@freeuk.com> - 2015-07-07 10:31 +0100
                Re: sprintf and the trailing null Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-07-07 02:51 -0700
                Re: sprintf and the trailing null Bartc <bc@freeuk.com> - 2015-07-07 12:10 +0100
                Re: sprintf and the trailing null Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-07-07 05:08 -0700
                Re: sprintf and the trailing null Bartc <bc@freeuk.com> - 2015-07-07 13:52 +0100
                Re: sprintf and the trailing null Phil Carmody <pc+usenet@asdf.org> - 2015-07-08 20:20 +0300
                Re: sprintf and the trailing null Bartc <bc@freeuk.com> - 2015-07-08 18:51 +0100
                Re: sprintf and the trailing null raltbos@xs4all.nl (Richard Bos) - 2015-07-09 10:27 +0000
                Re: sprintf and the trailing null Tim Rentsch <txr@alumni.caltech.edu> - 2015-07-10 19:03 -0700
              Re: sprintf and the trailing null gordonb.7tw58@burditt.org (Gordon Burditt) - 2015-07-07 15:40 -0500
                Re: sprintf and the trailing null "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-07-07 15:14 -0700
        Re: sprintf and the trailing null "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-07-06 07:27 -0700
          Re: sprintf and the trailing null jt@toerring.de (Jens Thoms Toerring) - 2015-07-06 16:46 +0000
        Re: sprintf and the trailing null Keith Thompson <kst-u@mib.org> - 2015-07-06 07:56 -0700
  Re: sprintf and the trailing null Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2015-07-06 09:32 -0600
  Re: sprintf and the trailing null Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-07-06 08:37 -0700
    Re: sprintf and the trailing null Keith Thompson <kst-u@mib.org> - 2015-07-06 08:54 -0700
  Re: sprintf and the trailing null "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-07-06 08:53 -0700
    Re: sprintf and the trailing null "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-07-06 09:00 -0700
    Re: sprintf and the trailing null Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-07-06 17:14 +0100
      Re: sprintf and the trailing null "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-07-06 09:24 -0700
        Re: sprintf and the trailing null "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-07-06 09:31 -0700
  Re: sprintf and the trailing null Sjouke Burry <burrynulnulfour@ppllaanneett.nnll> - 2015-07-07 01:43 +0200
    Re: sprintf and the trailing null "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-07-06 17:09 -0700
      Re: sprintf and the trailing null Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2015-07-06 21:08 -0600
        Re: sprintf and the trailing null "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-07-06 21:29 -0700
        Re: sprintf and the trailing null Phil Carmody <pc+usenet@asdf.org> - 2015-07-08 20:24 +0300
          Re: sprintf and the trailing null "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-07-08 10:44 -0700
  Re: sprintf and the trailing null Les Cargill <lcargill99@comcast.com> - 2015-07-07 21:48 -0500

csiph-web