Re: fseek under IBM MVS

From	Keith Thompson <kst-u@mib.org>
Newsgroups	comp.lang.c
Subject	Re: fseek under IBM MVS
Date	2014-12-19 08:08 -0800
Organization	None to speak of
Message-ID	<lntx0rbp20.fsf@nuthaus.mib.org> (permalink)
References	(8 earlier) <ln1tnxes0a.fsf@nuthaus.mib.org> <5492c2fc.401187@news.xs4all.nl> <54930469.3010102@verizon.net> <54940c6e.1006062@news.xs4all.nl> <m717m3$6lc$1@dont-email.me>

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James Kuyper <jameskuyper@verizon.net> writes:
> On 12/19/2014 06:31 AM, Richard Bos wrote:
>> James Kuyper <jameskuyper@verizon.net> wrote:
>>> On 12/18/2014 07:06 AM, Richard Bos wrote:
>>>> Sorry, typo/braino. I meant strncpy() and strncat().
>>>
>>> That makes more sense, though my own preferences differ. In most
>>> contexts in my code where I might need either one or the other of those,
>>> I already know the starting place for inserting new characters, and I
>>> need the unused portion of the array to be nulled out.  Every appearance
>>> of strncat() in code that I am currently responsible for was due to it
>>> being originally written by someone else.
>> 
>> Surprising. Do you work for the NSA, or for a business which has reason
>> to believe the NSA is on its case? Because I can think of no other good
>> reason why you'd want to do that.
>
> The field I'm filling in the output file has a fixed length. I'm using
> third-party library that copies an array of precisely that length into
> the file, including the part after the end of the string. If I allow
> random garbage to appear after the end of the string, output files that
> are functionally identical will compare different when using Unix
> utilities like cmp. This has bitten me often enough for me to decide it
> needs to be prevented. In some of the files I'm working on, every text
> field has a fixed length.

Do they allow storing an N-character string in an N-byte field (which
means it won't be null-terminated)?  That's exactly the data structure
strncpy() was designed for.  Of course you have to be careful not to
assume that there's a null terminator (and I have no doubt that you
are).

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"

Thread

fseek under IBM MVS jacob navia <jacob@spamsink.net> - 2014-12-14 22:16 +0100
  Re: fseek under IBM MVS glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-12-15 01:12 +0000
    Re: fseek under IBM MVS jacob navia <jacob@spamsink.net> - 2014-12-15 09:13 +0100
      Re: fseek under IBM MVS glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-12-15 09:22 +0000
  Re: fseek under IBM MVS Kaz Kylheku <kaz@kylheku.com> - 2014-12-15 16:26 +0000
    Re: fseek under IBM MVS raltbos@xs4all.nl (Richard Bos) - 2014-12-17 09:58 +0000
      Re: fseek under IBM MVS BartC <bc@freeuk.com> - 2014-12-17 11:29 +0000
  Re: fseek under IBM MVS John Bode <jfbode1029@gmail.com> - 2014-12-15 10:35 -0800
    Re: fseek under IBM MVS glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-12-15 21:33 +0000
      Re: fseek under IBM MVS jacob navia <jacob@spamsink.net> - 2014-12-15 23:45 +0100
        Re: fseek under IBM MVS Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2014-12-15 17:56 -0500
          Re: fseek under IBM MVS Kaz Kylheku <kaz@kylheku.com> - 2014-12-15 23:05 +0000
          Re: fseek under IBM MVS BartC <bc@freeuk.com> - 2014-12-15 23:19 +0000
            Re: fseek under IBM MVS Keith Thompson <kst-u@mib.org> - 2014-12-15 16:36 -0800
            Re: fseek under IBM MVS Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2014-12-15 20:42 -0500
          Re: fseek under IBM MVS jacob navia <jacob@spamsink.net> - 2014-12-16 01:00 +0100
        Re: fseek under IBM MVS glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-12-16 01:09 +0000
          Re: (OT) fseek under IBM MVS Vincenzo Mercuri <nomail@yahoo.it> - 2014-12-16 09:11 +0100
        Re: fseek under IBM MVS raltbos@xs4all.nl (Richard Bos) - 2014-12-17 10:06 +0000
          Re: fseek under IBM MVS jacob navia <jacob@spamsink.net> - 2014-12-17 11:33 +0100
            Re: fseek under IBM MVS John Bode <jfbode1029@gmail.com> - 2014-12-17 08:48 -0800
              Re: fseek under IBM MVS raltbos@xs4all.nl (Richard Bos) - 2014-12-17 17:26 +0000
              Re: fseek under IBM MVS jacob navia <jacob@spamsink.net> - 2014-12-17 19:46 +0100
                Re: fseek under IBM MVS Richard Heathfield <invalid@see.sig.invalid> - 2014-12-17 19:28 +0000
                Re: fseek under IBM MVS jacob navia <jacob@spamsink.net> - 2014-12-17 21:38 +0100
                Re: fseek under IBM MVS Richard Heathfield <invalid@see.sig.invalid> - 2014-12-17 21:05 +0000
                Re: fseek under IBM MVS Ian Collins <ian-news@hotmail.com> - 2014-12-18 11:37 +1300
                Re: fseek under IBM MVS John Bode <jfbode1029@gmail.com> - 2014-12-17 12:43 -0800
        Re: fseek under IBM MVS fir <profesor.fir@gmail.com> - 2014-12-19 08:35 -0800
          Re: fseek under IBM MVS BartC <bc@freeuk.com> - 2014-12-19 16:51 +0000
          Re: fseek under IBM MVS Robert Wessel <robertwessel2@yahoo.com> - 2014-12-19 16:36 -0600
    Re: fseek under IBM MVS raltbos@xs4all.nl (Richard Bos) - 2014-12-17 10:05 +0000
      Re: fseek under IBM MVS Keith Thompson <kst-u@mib.org> - 2014-12-17 09:05 -0800
        Re: fseek under IBM MVS raltbos@xs4all.nl (Richard Bos) - 2014-12-17 17:29 +0000
          Re: fseek under IBM MVS John Bode <jfbode1029@gmail.com> - 2014-12-17 12:55 -0800
            Re: fseek under IBM MVS John Bode <jfbode1029@gmail.com> - 2014-12-17 15:02 -0800
              Re: fseek under IBM MVS raltbos@xs4all.nl (Richard Bos) - 2014-12-17 23:37 +0000
                Re: fseek under IBM MVS Keith Thompson <kst-u@mib.org> - 2014-12-17 16:11 -0800
                Re: fseek under IBM MVS raltbos@xs4all.nl (Richard Bos) - 2014-12-18 12:06 +0000
                Re: fseek under IBM MVS James Kuyper <jameskuyper@verizon.net> - 2014-12-18 11:44 -0500
                Re: fseek under IBM MVS Keith Thompson <kst-u@mib.org> - 2014-12-18 11:03 -0800
                Re: fseek under IBM MVS raltbos@xs4all.nl (Richard Bos) - 2014-12-19 11:31 +0000
                Re: fseek under IBM MVS James Kuyper <jameskuyper@verizon.net> - 2014-12-19 08:03 -0500
                Re: fseek under IBM MVS Keith Thompson <kst-u@mib.org> - 2014-12-19 08:08 -0800
                Re: fseek under IBM MVS James Kuyper <jameskuyper@verizon.net> - 2014-12-19 11:30 -0500
              Re: fseek under IBM MVS Keith Thompson <kst-u@mib.org> - 2014-12-17 15:56 -0800
              Re: fseek under IBM MVS Ian Collins <ian-news@hotmail.com> - 2014-12-21 21:37 +1300
        Re: fseek under IBM MVS glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-12-17 21:59 +0000
          Re: fseek under IBM MVS Keith Thompson <kst-u@mib.org> - 2014-12-17 14:33 -0800
          Re: fseek under IBM MVS "Charles Richmond" <numerist@aquaporin4.com> - 2014-12-18 16:06 -0600
  Re: fseek under IBM MVS Siri Crews <chine.bleu@yahoo.com> - 2014-12-17 04:20 -0800

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