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Re: Method other than strlen to check for truncation with fgets?

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James Kuyper <jameskuyper@verizon.net> writes:

> On 05/07/2015 09:44 PM, Ben Bacarisse wrote:
>> Lőrinczy Zsigmond <zsiga@nospam.for.me> writes:
>> 
>>>>> The input might contain \0 so this method is unreliable.
>>>>
>>>> The method is reliable even if there are nulls in the input (provided
>>>> fgets processes them just like any other character).
>>>
>>> fgets does that alright, strlen doesn't.
>>>
>>> You still could check for more data after the first \0
>>> and find out how many \0 the input contained,
>>> but this method is neither efficient nor elegant.
>> 
>> So why use it?  I think I'm losing track of the point you are making.
>> The idea of marking the last buffer element with a non-null value is
>> reliable even in the presence of nulls in the input (which was, I
>> thought, your point).  The length of the input can be recovered very
>> simply -- it's sizeof buffer - 1 if the last element is now null, and
>> memchr(buffer, '\n', sizeof buffer) - buffer + 1 otherwise.
>> 
>
> if fgets() reaches end-of-file before reading in a newline, and before
> reaching the end of the buffer, then the last element will not be
> null,

Yes, good point.  It's too late for me (the election is keeping me up)
but a test for eof() could be used to about undefined behaviour.  Nulls
in an incomplete last line would still be a problem.

<snip>
-- 
Ben.

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Method other than strlen to check for truncation with fgets? mathog <dmathog@gmail.com> - 2015-05-06 12:35 -0700
  Re: Method other than strlen to check for truncation with fgets? Barry Schwarz <schwarzb@dqel.com> - 2015-05-06 15:14 -0700
    Re: Method other than strlen to check for truncation with fgets? mathog <dmathog@gmail.com> - 2015-05-06 16:14 -0700
      Re: Method other than strlen to check for truncation with fgets? Barry Schwarz <schwarzb@dqel.com> - 2015-05-06 17:51 -0700
      Re: Method other than strlen to check for truncation with fgets? Tim Rentsch <txr@alumni.caltech.edu> - 2015-05-06 18:23 -0700
        Re: Method other than strlen to check for truncation with fgets? mathog <dmathog@gmail.com> - 2015-05-07 10:07 -0700
          Re: Method other than strlen to check for truncation with fgets? Tim Rentsch <txr@alumni.caltech.edu> - 2015-05-07 16:06 -0700
  Re: Method other than strlen to check for truncation with fgets? James Kuyper <jameskuyper@verizon.net> - 2015-05-06 22:20 -0400
    Re: Method other than strlen to check for truncation with fgets? mathog <dmathog@gmail.com> - 2015-05-07 10:29 -0700
      Re: Method other than strlen to check for truncation with fgets? James Kuyper <jameskuyper@verizon.net> - 2015-05-07 14:09 -0400
        Re: Method other than strlen to check for truncation with fgets? mathog <dmathog@gmail.com> - 2015-05-07 12:48 -0700
          Re: Method other than strlen to check for truncation with fgets? James Kuyper <jameskuyper@verizon.net> - 2015-05-07 17:01 -0400
            Re: Method other than strlen to check for truncation with fgets? mathog <dmathog@gmail.com> - 2015-05-08 10:59 -0700
              Re: Method other than strlen to check for truncation with fgets? James Kuyper <jameskuyper@verizon.net> - 2015-05-08 14:48 -0400
              Re: Method other than strlen to check for truncation with fgets? glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-05-08 18:37 +0000
                Re: Method other than strlen to check for truncation with fgets? James Kuyper <jameskuyper@verizon.net> - 2015-05-08 15:06 -0400
  Re: Method other than strlen to check for truncation with fgets? Lőrinczy Zsigmond <nospam@for.me> - 2015-05-07 07:04 +0200
    Re: Method other than strlen to check for truncation with fgets? Richard Heathfield <rjh@cpax.org.uk> - 2015-05-07 06:52 +0100
      Re: Method other than strlen to check for truncation with fgets? Lőrinczy Zsigmond <zsiga@nospam.for.me> - 2015-05-07 09:58 +0200
        Re: Method other than strlen to check for truncation with fgets? Stephen Sprunk <stephen@sprunk.org> - 2015-05-07 09:12 -0500
        Re: Method other than strlen to check for truncation with fgets? Keith Thompson <kst-u@mib.org> - 2015-05-07 08:51 -0700
          Re: Method other than strlen to check for truncation with fgets? Lőrinczy Zsigmond <zsiga@nospam.for.me> - 2015-05-07 19:09 +0200
            Re: Method other than strlen to check for truncation with fgets? James Kuyper <jameskuyper@verizon.net> - 2015-05-07 14:15 -0400
    Re: Method other than strlen to check for truncation with fgets? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-05-07 11:31 +0100
      Re: Method other than strlen to check for truncation with fgets? Lőrinczy Zsigmond <zsiga@nospam.for.me> - 2015-05-07 15:41 +0200
        Re: Method other than strlen to check for truncation with fgets? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-05-08 02:44 +0100
          Re: Method other than strlen to check for truncation with fgets? James Kuyper <jameskuyper@verizon.net> - 2015-05-07 23:24 -0400
            Re: Method other than strlen to check for truncation with fgets? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-05-08 04:41 +0100
      Re: Method other than strlen to check for truncation with fgets? Keith Thompson <kst-u@mib.org> - 2015-05-07 08:49 -0700
        Re: Method other than strlen to check for truncation with fgets? James Kuyper <jameskuyper@verizon.net> - 2015-05-07 12:19 -0400
        Re: Method other than strlen to check for truncation with fgets? glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-05-07 18:08 +0000
    Re: Method other than strlen to check for truncation with fgets? James Kuyper <jameskuyper@verizon.net> - 2015-05-07 12:19 -0400
      Re: Method other than strlen to check for truncation with fgets? mathog <dmathog@gmail.com> - 2015-05-07 09:57 -0700
  Re: Method other than strlen to check for truncation with fgets? Siri Cruz <chine.bleu@yahoo.com> - 2015-05-07 11:31 -0700
    Re: Method other than strlen to check for truncation with fgets? Keith Thompson <kst-u@mib.org> - 2015-05-07 12:00 -0700
      Re: Method other than strlen to check for truncation with fgets? Siri Cruz <chine.bleu@yahoo.com> - 2015-05-07 12:44 -0700
        Re: Method other than strlen to check for truncation with fgets? Keith Thompson <kst-u@mib.org> - 2015-05-07 14:03 -0700
          Re: Method other than strlen to check for truncation with fgets? Siri Cruz <chine.bleu@yahoo.com> - 2015-05-07 15:28 -0700

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