Re: What is the difference between (r+ and w+)

Path	csiph.com!eternal-september.org!feeder.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail
From	Keith Thompson <kst-u@mib.org>
Newsgroups	comp.lang.c
Subject	Re: What is the difference between (r+ and w+)
Date	Sat, 17 Jun 2017 19:55:05 -0700
Organization	None to speak of
Lines	46
Message-ID	<lnvanuhunq.fsf@kst-u.example.com> (permalink)
References	<oi4ih6$5mi$1@gioia.aioe.org> <ln4lvejey6.fsf@kst-u.example.com> <oi4jq0$74j$1@gioia.aioe.org> <oi4l0m$vl6$1@jstuckle.eternal-september.org> <oi4mab$a0f$1@gioia.aioe.org>
Mime-Version	1.0
Content-Type	text/plain; charset=us-ascii
Injection-Info	mx02.eternal-september.org; posting-host="1d5a24d016722a50a74735015b7fb40e"; logging-data="25040"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX18yuZng3ckgA6qgmOhVPhDR"
User-Agent	Gnus/5.13 (Gnus v5.13) Emacs/23.1 (gnu/linux)
Cancel-Lock	sha1:PAorFGfw7GEnYyAFn0PBwqzagcw= sha1:6e3cLT1Rbix7/V3UvCcihTtWhKA=
Xref	csiph.com comp.lang.c:112430

Show key headers only | View raw

Christopher <invalid@invalid.invalid> writes:
> On 18/06/2017 02:32, Jerry Stuckle wrote:
>> On 6/17/2017 9:00 PM, Christopher wrote:
>>> On 18/06/2017 01:51, Keith Thompson wrote:
>>>> Christopher <invalid@invalid.invalid> writes:
>>>>> r+ Opens a text file to read from or write to
>>>>> w+ Opens a text file to write to or read from
>>>>>
>>>>> It looks exactly the same thing to me!!
>>>> What reference did you use?  Here's what the C standard says
>>>> (N1570 7.21.5.3p3):
>>>>
>>>>       r+   open text file for update (reading and writing)
>>>>       w+   truncate to zero length or create text file for update
>>>>
>>> This is a copy from the book!!
>>>
>>> <https://i.cubeupload.com/pdNkOH.png>
>> Yes, but although your book isn't very clear on this (at least not what
>> you posted - I don't know what the rest of the text says), these are
>> extensions of the "r" and "w" modes.
>>
>> "r" opens an existing file to read, while "r+ does the same but also
>> allows writing.
>>
>> "w" opens a file to write.  If one exists, it is truncated; otherwise a
>> new file is created.  "w+" does the same but also allows reading.
>>
>
> The book is pretty simple.  It is for newbies like me and it gives step 
> by step instructions of how to do things.  See this two page doc from 
> the book re files creation:
>
> <https://drive.google.com/file/d/0Bwx0lG_v1tcONExSejZWMGJaMUU/view?usp=sharing>

Does the book's author think that beginners don't need to know that "w+"
truncates an existing file?

That's twice you've posted excerpts from the book without identifying
it.  Are you keeping the title and author secret?

-- 
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

What is the difference between (r+ and w+) Christopher <invalid@invalid.invalid> - 2017-06-17 23:59 -0100
  Re: What is the difference between (r+ and w+) Keith Thompson <kst-u@mib.org> - 2017-06-17 17:51 -0700
    Re: What is the difference between (r+ and w+) Christopher <invalid@invalid.invalid> - 2017-06-18 00:00 -0100
      Re: What is the difference between (r+ and w+) Jerry Stuckle <jstucklex@attglobal.net> - 2017-06-17 21:32 -0400
        Re: What is the difference between (r+ and w+) Christopher <invalid@invalid.invalid> - 2017-06-18 00:50 -0100
          Re: What is the difference between (r+ and w+) Richard Heathfield <rjh@cpax.org.uk> - 2017-06-18 03:40 +0100
            Re: What is the difference between (r+ and w+) jacobnavia <jacob@jacob.remcomp.fr> - 2017-06-18 11:48 +0200
              Re: What is the difference between (r+ and w+) Richard Heathfield <rjh@cpax.org.uk> - 2017-06-18 13:13 +0100
                Re: What is the difference between (r+ and w+) Gareth Owen <gwowen@gmail.com> - 2017-06-18 16:20 +0100
            Re: What is the difference between (r+ and w+) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-06-18 14:49 +0100
              Re: What is the difference between (r+ and w+) Richard Heathfield <rjh@cpax.org.uk> - 2017-06-18 15:46 +0100
                Re: What is the difference between (r+ and w+) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-06-19 00:16 +0100
                Re: What is the difference between (r+ and w+) Richard Heathfield <rjh@cpax.org.uk> - 2017-06-19 05:37 +0100
                Re: What is the difference between (r+ and w+) Keith Thompson <kst-u@mib.org> - 2017-06-19 09:25 -0700
                Re: What is the difference between (r+ and w+) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-06-19 17:35 +0100
                Re: What is the difference between (r+ and w+) Richard Heathfield <rjh@cpax.org.uk> - 2017-06-19 18:19 +0100
                Re: What is the difference between (r+ and w+) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-06-19 20:51 +0100
                Re: What is the difference between (r+ and w+) Richard Heathfield <rjh@cpax.org.uk> - 2017-06-19 21:16 +0100
                Re: What is the difference between (r+ and w+) Tim Rentsch <txr@alumni.caltech.edu> - 2017-06-19 04:58 -0700
                Re: What is the difference between (r+ and w+) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-06-19 17:43 +0100
                Re: What is the difference between (r+ and w+) Tim Rentsch <txr@alumni.caltech.edu> - 2017-06-19 22:16 -0700
                Re: What is the difference between (r+ and w+) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-06-20 11:53 +0100
                Re: What is the difference between (r+ and w+) Tim Rentsch <txr@alumni.caltech.edu> - 2017-06-20 22:45 -0700
              Re: What is the difference between (r+ and w+) Good Guy <hello.world@example.com> - 2017-06-18 18:17 +0100
                Re: What is the difference between (r+ and w+) Richard Heathfield <rjh@cpax.org.uk> - 2017-06-18 18:20 +0100
                Re: What is the difference between (r+ and w+) bartc <bc@freeuk.com> - 2017-06-18 18:27 +0100
                Re: What is the difference between (r+ and w+) jacobnavia <jacob@jacob.remcomp.fr> - 2017-06-20 11:11 +0200
                Re: What is the difference between (r+ and w+) bartc <bc@freeuk.com> - 2017-06-20 10:27 +0100
                Re: What is the difference between (r+ and w+) Richard Heathfield <rjh@cpax.org.uk> - 2017-06-20 10:54 +0100
                Re: What is the difference between (r+ and w+) jacobnavia <jacob@jacob.remcomp.fr> - 2017-06-20 12:25 +0200
                Re: What is the difference between (r+ and w+) Richard Heathfield <rjh@cpax.org.uk> - 2017-06-20 12:34 +0100
                Re: What is the difference between (r+ and w+) jameskuyper@verizon.net - 2017-06-20 05:37 -0700
                Re: What is the difference between (r+ and w+) Richard Heathfield <rjh@cpax.org.uk> - 2017-06-20 14:11 +0100
                Re: What is the difference between (r+ and w+) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-06-20 14:35 +0100
                Re: What is the difference between (r+ and w+) raltbos@xs4all.nl (Richard Bos) - 2017-06-18 17:30 +0000
                Re: What is the difference between (r+ and w+) Richard Heathfield <rjh@cpax.org.uk> - 2017-06-18 21:21 +0100
                Re: What is the difference between (r+ and w+) Richard Heathfield <rjh@cpax.org.uk> - 2017-06-18 21:23 +0100
                Re: What is the difference between (r+ and w+) Richard Heathfield <rjh@cpax.org.uk> - 2017-06-18 21:47 +0100
                Re: What is the difference between (r+ and w+) Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2017-06-18 17:01 -0400
                Re: What is the difference between (r+ and w+) "James R. Kuyper" <jameskuyper@verizon.net> - 2017-06-19 10:41 -0400
                Re: What is the difference between (r+ and w+) Richard Heathfield <rjh@cpax.org.uk> - 2017-06-18 21:50 +0100
                Re: What is the difference between (r+ and w+) Keith Thompson <kst-u@mib.org> - 2017-06-18 13:52 -0700
                Re: What is the difference between (r+ and w+) jacobnavia <jacob@jacob.remcomp.fr> - 2017-06-20 11:16 +0200
                Re: What is the difference between (r+ and w+) raltbos@xs4all.nl (Richard Bos) - 2017-06-26 15:54 +0000
                Re: What is the difference between (r+ and w+) Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2017-06-18 17:13 -0400
                Re: What is the difference between (r+ and w+) Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2017-06-18 17:17 -0400
                Re: What is the difference between (r+ and w+) Keith Thompson <kst-u@mib.org> - 2017-06-18 15:14 -0700
                Re: What is the difference between (r+ and w+) Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2017-06-18 18:24 -0400
                Re: What is the difference between (r+ and w+) Tim Rentsch <txr@alumni.caltech.edu> - 2017-06-19 04:11 -0700
                Re: What is the difference between (r+ and w+) Richard Heathfield <rjh@cpax.org.uk> - 2017-06-18 23:01 +0100
          Re: What is the difference between (r+ and w+) Keith Thompson <kst-u@mib.org> - 2017-06-17 19:55 -0700
            Re: What is the difference between (r+ and w+) Christopher <invalid@invalid.invalid> - 2017-06-18 02:10 -0100
              Re: What is the difference between (r+ and w+) Richard Heathfield <rjh@cpax.org.uk> - 2017-06-18 04:15 +0100
              Re: What is the difference between (r+ and w+) raltbos@xs4all.nl (Richard Bos) - 2017-06-18 08:31 +0000
                Re: What is the difference between (r+ and w+) Good Guy <hello.world@example.com> - 2017-06-18 18:28 +0100
                Re: What is the difference between (r+ and w+) Keith Thompson <kst-u@mib.org> - 2017-06-18 11:25 -0700
                Re: What is the difference between (r+ and w+) raltbos@xs4all.nl (Richard Bos) - 2017-06-18 19:13 +0000
                Re: What is the difference between (r+ and w+) David Kleinecke <dkleinecke@gmail.com> - 2017-06-18 14:30 -0700
                Re: What is the difference between (r+ and w+) Richard Heathfield <rjh@cpax.org.uk> - 2017-06-18 23:04 +0100
              Re: What is the difference between (r+ and w+) GOTHIER Nathan <nathan.gothier@gmail.com> - 2017-06-18 10:43 +0200
                Re: What is the difference between (r+ and w+) Jerry Stuckle <jstucklex@attglobal.net> - 2017-06-18 10:33 -0400
                Re: What is the difference between (r+ and w+) GOTHIER Nathan <nathan.gothier@gmail.com> - 2017-06-19 01:27 +0200
                Re: What is the difference between (r+ and w+) Jerry Stuckle <jstucklex@attglobal.net> - 2017-06-18 21:16 -0400
      Re: What is the difference between (r+ and w+) Ian Collins <ian-news@hotmail.com> - 2017-06-18 13:45 +1200
      Re: What is the difference between (r+ and w+) Keith Thompson <kst-u@mib.org> - 2017-06-17 19:05 -0700

csiph-web