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Groups > alt.os.development > #8362
| From | "Rod Pemberton" <boo@fasdfrewar.cdm> |
|---|---|
| Newsgroups | alt.os.development |
| Subject | Re: Smaller C |
| Date | 2015-07-13 23:13 -0400 |
| Organization | Aioe.org NNTP Server |
| Message-ID | <op.x1qtwod5yfako5@localhost> (permalink) |
| References | (14 earlier) <79c0cfce-38ec-4bcc-bd5f-a25808ffb8ea@googlegroups.com> <39da71f8-7e21-4fcb-84da-263d5c81059f@googlegroups.com> <op.x1nizmxyyfako5@localhost> <mnuak9$f21$1@dont-email.me> <mo02q5$i3g$1@speranza.aioe.org> |
On Mon, 13 Jul 2015 06:10:14 -0400, James Harris
<james.harris.1@gmail.com> wrote:
[...]
> As stdin, stdout and stderr are pointers that it should be possible
> to change
...
> I don't see how they can be constants, at least in a conforming
> implementation.
Most C implementations treat them as constants. GCC is non-standard
here. GCC argues that the C specification doesn't require static
pointers for stdin, stdout, stderr. Apparently, they do this to
allow GCC to reassign streams, e.g., pipes.
> I have been looking at freopen() and it is a bit of a weird one. The
> signature is
>
> FILE *freopen(const char *path, const char *mode, FILE *stream);
>
> The path and the mode are as in the fopen call but note that freopen
> has *two* file pointers.
It really has only *one* file pointer ...
According to H&S, not the C specifications, the return file pointer
must be either the passed file pointer 'stream' or NULL for failure.
I.e., FILE *stream is passed back as the return FILE * unless it needs
to be set to NULL for failure.
freopen() fclose's stream, fopen's path/mode, associates path/mode
with stream instead of using a new file pointer.
> After some digging I think that the parameter FILE* is the stream that
> should be reopened (repointed, if you like).
Yes.
> The return FILE* is only specified to be a FILE pointer
... and will be either 'stream' or NULL. See above.
> "Upon successful completion fopen(), fdopen() and freopen() return
> a FILE pointer"
>
> But it doesn't say what file it will point at.
For fopen(), it will be the newly opened file ... or NULL.
For freopen(), it will be the path/mode you passed, using the original
'stream' file pointer, or it'll return NULL for failure.
fdopen() must be POSIX or Linux.
> I can only guess that the
> freopen call changes the parameter FILE pointer in some way and also
> returns it the new value. The return is possibly there just to indicate
> success (or failure if NULL).
Changes?
> A valid call, then, might be
>
> if (freopen("prog.c", "r", stdin)) ....
>
> I still don't understand how that can change stdin unless freopen is a
> macro. But it's not important. It is something I may never use.
Why would there need to be any change? ...
Rod Pemberton
--
Tolerance and socialism attracts intolerance and terrorism. See:
France, United Kingdom, Germany, Denmark, Belgium, Netherlands, ...
UK: Strong encryption, non-issue. GR: Eurozone currency, priority.
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Re: Smaller C "Alexei A. Frounze" <alexfrunews@gmail.com> - 2015-07-11 20:39 -0700
Re: Smaller C "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-07-12 04:24 -0400
Re: Smaller C "Alexei A. Frounze" <alexfrunews@gmail.com> - 2015-07-12 03:17 -0700
Re: Smaller C "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-07-13 03:28 -0400
Re: Smaller C "James Harris" <james.harris.1@gmail.com> - 2015-07-12 19:12 +0100
Re: Smaller C "Alexei A. Frounze" <alexfrunews@gmail.com> - 2015-07-12 17:09 -0700
Re: Smaller C "James Harris" <james.harris.1@gmail.com> - 2015-07-13 11:10 +0100
Re: Smaller C "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-07-13 23:13 -0400
Re: Smaller C "James Harris" <james.harris.1@gmail.com> - 2015-07-14 09:08 +0100
Re: Smaller C "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-07-15 02:23 -0400
Re: Smaller C "Alexei A. Frounze" <alexfrunews@gmail.com> - 2015-08-15 02:12 -0700
Re: Smaller C "Alexei A. Frounze" <alexfrunews@gmail.com> - 2015-09-06 15:54 -0700
Re: Smaller C "Benjamin David Lunt" <zfysz@fysnet.net> - 2015-09-07 12:19 -0700
Re: Smaller C "Alexei A. Frounze" <alexfrunews@gmail.com> - 2015-09-07 13:30 -0700
Re: Smaller C "Benjamin David Lunt" <zfysz@fysnet.net> - 2015-09-09 19:38 -0700
Re: Smaller C "Benjamin David Lunt" <zfysz@fysnet.net> - 2015-09-09 19:49 -0700
Re: Smaller C "Benjamin David Lunt" <zfysz@fysnet.net> - 2015-09-09 20:58 -0700
Re: Smaller C "Alexei A. Frounze" <alexfrunews@gmail.com> - 2015-09-10 01:45 -0700
Re: Smaller C "Benjamin David Lunt" <zfysz@fysnet.net> - 2015-09-10 10:45 -0700
Re: Smaller C "Alexei A. Frounze" <alexfrunews@gmail.com> - 2015-09-10 23:20 -0700
Re: Smaller C "wolfgang kern" <nowhere@never.at> - 2015-09-11 09:26 +0200
Re: Smaller C "wolfgang kern" <nowhere@never.at> - 2015-09-11 09:50 +0200
Re: Smaller C "Alexei A. Frounze" <alexfrunews@gmail.com> - 2015-09-11 00:58 -0700
Re: Smaller C "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-09-11 17:38 -0400
Re: Smaller C "James Harris" <james.harris.1@gmail.com> - 2015-09-11 23:39 +0100
Re: Smaller C "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-09-11 19:39 -0400
Re: Smaller C "James Harris" <james.harris.1@gmail.com> - 2015-09-12 11:22 +0100
Re: Smaller C "Alexei A. Frounze" <alexfrunews@gmail.com> - 2015-09-12 02:21 -0700
Re: Smaller C "wolfgang kern" <nowhere@never.at> - 2015-09-12 21:53 +0200
Re: Smaller C "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-09-13 03:37 -0400
Re: Smaller C "James Harris" <james.harris.1@gmail.com> - 2015-09-13 09:49 +0100
Re: Smaller C "wolfgang kern" <nowhere@never.at> - 2015-09-13 12:58 +0200
Re: Smaller C "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-09-13 07:32 -0400
Re: Smaller C "James Harris" <james.harris.1@gmail.com> - 2015-09-13 19:05 +0100
Re: Smaller C "James Harris" <james.harris.1@gmail.com> - 2015-09-14 13:19 +0100
Re: Smaller C "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-09-15 00:01 -0400
Re: Smaller C "James Harris" <james.harris.1@gmail.com> - 2015-09-18 14:48 +0100
Re: Smaller C "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-09-26 16:23 -0400
Re: Smaller C James Harris <james.harris.1@gmail.com> - 2015-09-27 00:23 +0100
Re: Smaller C "Alexei A. Frounze" <alexfrunews@gmail.com> - 2015-09-26 16:37 -0700
Re: Smaller C "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-09-27 10:17 -0400
Re: Smaller C "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-09-27 10:24 -0400
Re: Smaller C "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-09-27 10:46 -0400
Re: Smaller C James Harris <james.harris.1@gmail.com> - 2016-01-16 16:14 +0000
Re: Smaller C Rod Pemberton <NoHaveNotOne@bcczxcfre.cmm> - 2016-01-23 13:20 -0500
Re: Smaller C James Harris <james.harris.1@gmail.com> - 2016-01-27 13:52 +0000
Re: Smaller C "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-09-27 10:28 -0400
Re: Smaller C James Harris <james.harris.1@gmail.com> - 2016-01-16 16:31 +0000
Re: Smaller C Rod Pemberton <NoHaveNotOne@bcczxcfre.cmm> - 2016-01-23 13:20 -0500
Re: Smaller C "James Harris" <james.harris.1@gmail.com> - 2015-09-18 16:21 +0100
Re: Smaller C "Alexei A. Frounze" <alexfrunews@gmail.com> - 2015-09-20 17:25 -0700
Re: Smaller C "wolfgang kern" <nowhere@never.at> - 2015-09-13 12:43 +0200
Re: Smaller C "James Harris" <james.harris.1@gmail.com> - 2015-09-13 09:21 +0100
Re: Smaller C "wolfgang kern" <nowhere@never.at> - 2015-09-13 13:02 +0200
Re: Smaller C "James Harris" <james.harris.1@gmail.com> - 2015-09-13 19:09 +0100
Re: Smaller C "Benjamin David Lunt" <zfysz@fysnet.net> - 2015-09-11 13:32 -0700
Re: Smaller C "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-09-11 18:51 -0400
Re: Smaller C "Benjamin David Lunt" <zfysz@fysnet.net> - 2015-09-11 18:16 -0700
Re: Smaller C "Alexei A. Frounze" <alexfrunews@gmail.com> - 2015-09-12 02:36 -0700
Re: Smaller C "James Harris" <james.harris.1@gmail.com> - 2015-09-12 11:56 +0100
Re: Smaller C "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-09-13 03:45 -0400
Re: Smaller C "James Harris" <james.harris.1@gmail.com> - 2015-09-13 10:28 +0100
Re: Smaller C "Alexei A. Frounze" <alexfrunews@gmail.com> - 2015-09-13 02:53 -0700
Re: Smaller C "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-09-13 11:17 -0400
Re: Smaller C "Alexei A. Frounze" <alexfrunews@gmail.com> - 2015-09-13 16:54 -0700
Re: Smaller C "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-09-13 21:39 -0400
Re: Smaller C "Alexei A. Frounze" <alexfrunews@gmail.com> - 2015-09-13 20:31 -0700
Re: Smaller C "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-09-13 09:03 -0400
Re: Smaller C "James Harris" <james.harris.1@gmail.com> - 2015-09-13 19:48 +0100
Re: Smaller C "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-09-13 21:33 -0400
Re: Smaller C "James Harris" <james.harris.1@gmail.com> - 2015-09-14 23:17 +0100
Re: Smaller C "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-09-20 17:37 -0400
Re: Smaller C "James Harris" <james.harris.1@gmail.com> - 2015-09-20 23:46 +0100
Re: Smaller C "Benjamin David Lunt" <zfysz@fysnet.net> - 2015-09-11 21:37 -0700
Re: Smaller C "Benjamin David Lunt" <zfysz@fysnet.net> - 2015-09-11 22:29 -0700
Re: Smaller C "Alexei A. Frounze" <alexfrunews@gmail.com> - 2015-09-12 03:25 -0700
Re: Smaller C "Benjamin David Lunt" <zfysz@fysnet.net> - 2015-09-12 11:18 -0700
Re: Smaller C "Benjamin David Lunt" <zfysz@fysnet.net> - 2015-09-12 11:39 -0700
Re: Smaller C "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-09-13 03:47 -0400
Re: Smaller C "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-09-13 11:31 -0400
Re: Smaller C "Alexei A. Frounze" <alexfrunews@gmail.com> - 2015-09-13 02:00 -0700
Re: Smaller C "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-09-13 11:31 -0400
Re: Smaller C "Benjamin David Lunt" <zfysz@fysnet.net> - 2015-09-13 09:15 -0700
Re: Smaller C "Alexei A. Frounze" <alexfrunews@gmail.com> - 2015-09-12 02:45 -0700
Re: Smaller C "Benjamin David Lunt" <zfysz@fysnet.net> - 2015-09-12 10:55 -0700
Re: Smaller C "Benjamin David Lunt" <zfysz@fysnet.net> - 2015-09-15 19:23 -0700
Re: Smaller C "Alexei A. Frounze" <alexfrunews@gmail.com> - 2015-09-16 03:03 -0700
Re: Smaller C "Benjamin David Lunt" <zfysz@fysnet.net> - 2015-09-16 10:17 -0700
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