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Re: Working with files on different operating systems

From Ben Bacarisse <ben.usenet@bsb.me.uk>
Newsgroups comp.lang.c
Subject Re: Working with files on different operating systems
Date 2015-10-09 11:13 +0100
Organization A noiseless patient Spider
Message-ID <87twq0jqo5.fsf@bsb.me.uk> (permalink)
References <mv7b7l$gru$1@speranza.aioe.org> <mv7id4$duj$1@dont-email.me>

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Les Cargill <lcargill99@comcast.com> writes:
<snip>
>> That way, the code for reading a file and reading a stream for example
>> from the network is the same.
>
> Are you familiar with select/poll/epoll? Might be time to
> learn about them; this is a good ( albeit tedious ) way to
> unify these things.

For some tasks, fgetc works just as well!

<snip>
> Your original plan should be just fine. This is the way I have
> determined file sizes since the 20th Century, modulo declariong
> and initializing things at the same time for some cruder toolchains:
>
> FILE *f = fopen(....);
>
> int rc = fseek(f,SEEK_END,0L);
> int len = ftell(f);
> rc = fseek(f,SEEK_SET,0L);
>
> after which, the file is nicely rewound and len contains the total
> number of octets in the file.
>
> Obviously  for some file systems this may not work, but those are
> hard to find now.

You can't rewind many kinds of stream, and that's as true today as it
ever was.

To the OP: there's no obvious reason for you to know the input size
before you parse it.  Are you storing it whole for some purpose that has
eluded me?  If so, you will have to avoid knowing the size if you want
to handle the widest range in input sources.

-- 
Ben.

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Thread

Working with files on different operating systems "Morten W. Petersen" <morphex@gmail.com> - 2015-10-09 05:11 +0200
  Re: Working with files on different operating systems Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2015-10-08 22:12 -0600
  Re: Working with files on different operating systems Les Cargill <lcargill99@comcast.com> - 2015-10-09 00:18 -0500
    Re: Working with files on different operating systems Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-09 11:13 +0100
      Re: Working with files on different operating systems "Morten W. Petersen" <morphex@gmail.com> - 2015-10-09 18:05 +0200
        Re: Working with files on different operating systems Les Cargill <lcargill99@comcast.com> - 2015-10-09 12:49 -0500
        Re: Working with files on different operating systems Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-10-09 17:32 -0400
        Re: Working with files on different operating systems Ian Collins <ian-news@hotmail.com> - 2015-10-10 12:37 +1300
      Re: Working with files on different operating systems Les Cargill <lcargill99@comcast.com> - 2015-10-09 12:48 -0500
        Re: Working with files on different operating systems Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-09 19:53 +0100
          Re: Working with files on different operating systems "Morten W. Petersen" <morphex@gmail.com> - 2015-10-09 21:09 +0200
            Re: Working with files on different operating systems Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-09 20:28 +0100
              Re: Working with files on different operating systems "Morten W. Petersen" <morphex@gmail.com> - 2015-10-09 21:40 +0200
                Re: Working with files on different operating systems James Kuyper <jameskuyper@verizon.net> - 2015-10-09 15:59 -0400
                Re: Working with files on different operating systems "Morten W. Petersen" <morphex@gmail.com> - 2015-10-09 22:07 +0200
                Re: Working with files on different operating systems James Kuyper <jameskuyper@verizon.net> - 2015-10-09 16:24 -0400
                Re: Working with files on different operating systems "Morten W. Petersen" <morphex@gmail.com> - 2015-10-10 03:08 +0200
                Re: Working with files on different operating systems Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-09 21:50 +0100
        Re: Working with files on different operating systems James Kuyper <jameskuyper@verizon.net> - 2015-10-09 14:54 -0400
          Re: Working with files on different operating systems "Morten W. Petersen" <morphex@gmail.com> - 2015-10-09 21:05 +0200
            Re: Working with files on different operating systems "Morten W. Petersen" <morphex@gmail.com> - 2015-10-09 21:47 +0200
            Re: Working with files on different operating systems James Kuyper <jameskuyper@verizon.net> - 2015-10-09 15:53 -0400
              Re: Working with files on different operating systems "Morten W. Petersen" <morphex@gmail.com> - 2015-10-09 22:01 +0200
                Re: Working with files on different operating systems James Kuyper <jameskuyper@verizon.net> - 2015-10-09 16:05 -0400
          Re: Working with files on different operating systems glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-10 01:16 +0000
            Re: Working with files on different operating systems "Morten W. Petersen" <morphex@gmail.com> - 2015-10-10 03:46 +0200
            Re: Working with files on different operating systems Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-10-10 08:08 -0400
          Re: Working with files on different operating systems raltbos@xs4all.nl (Richard Bos) - 2015-10-10 17:02 +0000
        Re: Working with files on different operating systems Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-10-09 15:53 -0400
    Re: Working with files on different operating systems "Morten W. Petersen" <morphex@gmail.com> - 2015-10-09 18:00 +0200
      Re: Working with files on different operating systems Les Cargill <lcargill99@comcast.com> - 2015-10-09 12:59 -0500
        Re: Working with files on different operating systems Keith Thompson <kst-u@mib.org> - 2015-10-09 12:37 -0700
          Re: Working with files on different operating systems Les Cargill <lcargill99@comcast.com> - 2015-10-09 17:36 -0500
            Re: Working with files on different operating systems Keith Thompson <kst-u@mib.org> - 2015-10-09 16:52 -0700
              Re: Working with files on different operating systems raltbos@xs4all.nl (Richard Bos) - 2015-10-14 11:27 +0000
                Re: Working with files on different operating systems James Kuyper <jameskuyper@verizon.net> - 2015-10-14 11:27 -0400
                Re: Working with files on different operating systems Jorgen Grahn <grahn+nntp@snipabacken.se> - 2015-10-14 16:46 +0000
                Re: Working with files on different operating systems Keith Thompson <kst-u@mib.org> - 2015-10-14 10:18 -0700
              Re: Working with files on different operating systems Les Cargill <lcargill99@comcast.com> - 2015-10-14 23:06 -0500
    Re: Working with files on different operating systems Keith Thompson <kst-u@mib.org> - 2015-10-09 09:16 -0700
      Re: Working with files on different operating systems Les Cargill <lcargill99@comcast.com> - 2015-10-09 17:43 -0500
        Re: Working with files on different operating systems Keith Thompson <kst-u@mib.org> - 2015-10-09 16:57 -0700
          Re: Working with files on different operating systems Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-10-09 22:41 -0700
    Re: Working with files on different operating systems David Thompson <dave.thompson2@verizon.net> - 2015-10-31 06:50 -0400
  Re: Working with files on different operating systems Siri Cruz <chine.bleu@yahoo.com> - 2015-10-08 23:25 -0700
    Re: Working with files on different operating systems Geoff <geoff@invalid.invalid> - 2015-10-10 10:35 -0700
  Re: Working with files on different operating systems Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-10-09 08:42 -0400
    Re: Working with files on different operating systems "Morten W. Petersen" <morphex@gmail.com> - 2015-10-09 18:51 +0200
      Re: Working with files on different operating systems Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-10-15 18:09 -0700
        Re: Working with files on different operating systems "Morten W. Petersen" <morphex@gmail.com> - 2015-10-17 04:01 +0200
          Re: Working with files on different operating systems Ian Collins <ian-news@hotmail.com> - 2015-10-17 15:55 +1300
            Re: Working with files on different operating systems Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-10-16 20:09 -0700
              Re: Working with files on different operating systems Ian Collins <ian-news@hotmail.com> - 2015-10-17 16:36 +1300
            Re: Working with files on different operating systems "Morten W. Petersen" <morphex@gmail.com> - 2015-10-17 05:10 +0200
        Re: Working with files on different operating systems supercat@casperkitty.com - 2015-10-31 12:05 -0700
          Re: Working with files on different operating systems Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-10-31 12:42 -0700
            Re: Working with files on different operating systems supercat@casperkitty.com - 2015-10-31 13:40 -0700
          Re: Working with files on different operating systems Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-31 19:55 +0000
            Re: Working with files on different operating systems supercat@casperkitty.com - 2015-10-31 13:43 -0700
              Re: Working with files on different operating systems Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-31 21:38 +0000

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