C Text/Binary Files

[Bartc]

The stdin/stdout files of C seem to be always in Text mode.

Is there any way of running a C program so that these (but especially
stdout) are in Binary mode instead?

(I'm in the process of wrapping a different language around C which doesn't
want the concept of text and binary files. But if I output a string such as
"ONE\nTWO\n ", this will behave differently between stdout and a regular
(binary) file. Examples on my OS:

"\n" Output 13,10 in text mode; 10 in binary mode
"\w" Output 13,13,10 in text mode; 13,10 in binary mode

(\w is a new escape code equivalent to \r\n). Workarounds will be awkward
(and I could never stop \n expanding to 13,10 for stdout) so would be nice
to avoid them)

--
Thanks,

Bartc

[pete]

Re: C Text/Binary Files

Bartc wrote:

The stdin/stdout files of C seem to be always in Text mode.

That's what the standards say.

--
pete

[santosh]

Re: C Text/Binary Files

Bartc wrote:

The stdin/stdout files of C seem to be always in Text mode.
>
Is there any way of running a C program so that these (but especially
stdout) are in Binary mode instead?

Yes, use freopen like this:

FILE *fin, *fout, *ferr;

fin = freopen(NULL, "rb", stdin);
fout = freopen(NULL, "ab", stdout);
ferr = freopen(NULL, "ab", stderr);

You could assign the return value to stdin, stdout and stderr itself,
but the standards says that they are not necessarily modifiable
lvalues. However it will probably work on most systems you would care
about.

See section 7.19.5.4 of the standard for details.

<snip>

[Ben Bacarisse]

Re: C Text/Binary Files

santosh <santosh.k83@gm ail.comwrites:

Bartc wrote:
>

>The stdin/stdout files of C seem to be always in Text mode.
>>
>Is there any way of running a C program so that these (but especially
>stdout) are in Binary mode instead?

>
Yes, use freopen like this:
>
FILE *fin, *fout, *ferr;
>
fin = freopen(NULL, "rb", stdin);
fout = freopen(NULL, "ab", stdout);
ferr = freopen(NULL, "ab", stderr);
>
You could assign the return value to stdin, stdout and stderr itself,
but the standards says that they are not necessarily modifiable
lvalues. However it will probably work on most systems you would care
about.

More importantly, freopen is not guaranteed to do what Bartc wants.
Thus the key information is not what the standard says but what
typical implementations do on systems where there is difference
between text and binary mode. I can give only one data point:
lcc-win32 returns NULL from the freopen call (for stdout).

--
Ben.

[santosh]

Re: C Text/Binary Files

Ben Bacarisse wrote:

santosh <santosh.k83@gm ail.comwrites:
>

>Bartc wrote:
>>

>>The stdin/stdout files of C seem to be always in Text mode.
>>>
>>Is there any way of running a C program so that these (but
>>especially stdout) are in Binary mode instead?

>>
>Yes, use freopen like this:
>>
> FILE *fin, *fout, *ferr;
>>
> fin = freopen(NULL, "rb", stdin);
> fout = freopen(NULL, "ab", stdout);
> ferr = freopen(NULL, "ab", stderr);
>>
>You could assign the return value to stdin, stdout and stderr itself,
>but the standards says that they are not necessarily modifiable
>lvalues. However it will probably work on most systems you would care
>about.

>
More importantly, freopen is not guaranteed to do what Bartc wants.
Thus the key information is not what the standard says but what
typical implementations do on systems where there is difference
between text and binary mode. I can give only one data point:
lcc-win32 returns NULL from the freopen call (for stdout).

And it similarly fails for stdin too. It's perhaps surprising that it
should fail. What difficulty would an implementation like win-lcc have
with this?

[Ali Karaali]

Re: C Text/Binary Files

>

See section 7.19.5.4 of the standard for details.
>
<snip>

Anyway, How can I find out standard's documents?

[Bartc]

Re: C Text/Binary Files

"Bartc" <bc@freeuk.comw rote in message
news:LCA7k.1408 8$E41.12364@tex t.news.virginme dia.com...

The stdin/stdout files of C seem to be always in Text mode.

Thanks for the replies.

I think if I use exclusively "\w" for newlines (ie. "\r\n") in strings and
internal functions that generate newlines, then this will work for binary
files.

For stdout, this will generate (on my OS) 13,13,10, but for console output
that is not critical. The only problem will be when stdout is piped or
redirected to a file at the OS command line, then I will need to process the
output to take out the extra 13.

I can live with that.

I have tried freopen() as suggested, and that sort of works, but output is
then sent to a file. So this is an alternative perhaps to redirection by the
OS and the mode /will/ be binary.

--
Bartc

[Ben Bacarisse]

Re: C Text/Binary Files

Ali Karaali <alicpp@gmail.c omwrites:

>>
>See section 7.19.5.4 of the standard for details.
>>
><snip>

>
Anyway, How can I find out standard's documents?

http://www.open-std.org/jtc1/sc22/wg...docs/n1256.pdf is a recent
draft of C99. The same site has lots of other useful documents.

--
Ben.

[rahul]

Re: C Text/Binary Files

On Jun 23, 8:21 am, santosh <santosh....@gm ail.comwrote:

And it similarly fails for stdin too. It's perhaps surprising that it
should fail. What difficulty would an implementation like win-lcc have
with this?

The following works for me:
#include <stdio.h>
#include <stdlib.h>

int
main(void) {
stdout = freopen(NULL, "ab", stdout);
return 0;
}

I compiled that with gcc on Linux. It works probably because Linux/
Unix does not distinguish between text and binary mode.

[Richard Bos]

Re: C Text/Binary Files

santosh <santosh.k83@gm ail.comwrote:

Bartc wrote:
>

The stdin/stdout files of C seem to be always in Text mode.

Is there any way of running a C program so that these (but especially
stdout) are in Binary mode instead?

>
Yes, use freopen like this:
>
FILE *fin, *fout, *ferr;
>
fin = freopen(NULL, "rb", stdin);
fout = freopen(NULL, "ab", stdout);
ferr = freopen(NULL, "ab", stderr);

Note that freopen() with a null first argument is new in C99. In C89,
you had to give a new file name.

Richard

[Keith Thompson]

Re: C Text/Binary Files

"Bartc" <bc@freeuk.comw rites:

"Bartc" <bc@freeuk.comw rote in message
news:LCA7k.1408 8$E41.12364@tex t.news.virginme dia.com...

The stdin/stdout files of C seem to be always in Text mode.

>
Thanks for the replies.
>
I think if I use exclusively "\w" for newlines (ie. "\r\n") in strings and
internal functions that generate newlines, then this will work for binary
files.

[...]

What is "\w"? It's not a standard escape sequence; its value is
implementation-defined.

--
Keith Thompson (The_Other_Keit h) kst-u@mib.org <http://www.ghoti.net/~kst>
Nokia
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"

[Harald van =?UTF-8?b?RMSzaw==?=]

Re: C Text/Binary Files

On Mon, 23 Jun 2008 12:59:01 -0700, Keith Thompson wrote:

What is "\w"? It's not a standard escape sequence; its value is
implementation-defined.

"\w" does not match the syntax of a string literal, so by the rule of the
longest match this is tokenised as {"}{\}{w}{"} . The behaviour is
undefined if a double quote character occurs as a single token. There need
not be any value given to "\w", and if there is, it need not be documented.

[Bartc]

Re: C Text/Binary Files


"Keith Thompson" <kst@cts.comwro te in message
news:lzk5gfkjne .fsf@stalkings. ghoti.net...

"Bartc" <bc@freeuk.comw rites:

>"Bartc" <bc@freeuk.comw rote in message
>news:LCA7k.140 88$E41.12364@te xt.news.virginm edia.com...

The stdin/stdout files of C seem to be always in Text mode.

>>
>Thanks for the replies.
>>
>I think if I use exclusively "\w" for newlines (ie. "\r\n") in strings
>and
>internal functions that generate newlines, then this will work for binary
>files.

[...]
>
What is "\w"? It's not a standard escape sequence; its value is
implementation-defined.

Sorry. In my original post I'd indicated (not very clearly) that \w was a
new escape in a language I was creating to wrap around C.

So it's not a C escape but is translated to "\r\n". It represents 'windows
newline'; (or more generally, the full newline sequence used in the target
OS).

--
Bartc

[Keith Thompson]

Re: C Text/Binary Files

Harald van Dþÿ3k <truedfx@gmail. comwrites:

On Mon, 23 Jun 2008 12:59:01 -0700, Keith Thompson wrote:

What is "\w"? It's not a standard escape sequence; its value is
implementation-defined.

>
"\w" does not match the syntax of a string literal, so by the rule
of the longest match this is tokenised as {"}{\}{w}{"} . The
behaviour is undefined if a double quote character occurs as a
single token. There need not be any value given to "\w", and if
there is, it need not be documented.

I believe you're mostly or entirely right, and I was wrong.

I misinterpreted the second clause of C99 6.4.4.4p10:

The value of an integer character constant containing more than
one character (e.g., 'ab'), or containing a character or escape
sequence that does not map to a single-byte execution character,
is implementation-defined.

as applying to things like '\w'; instead, it applies to things like
'\xffffffff'.

"\w" is split into 4 preprocessor tokens:
" \ w "
The " is not a punctuator; it's in the category "each non-white-space
character that cannot be one of the above" (C99 6.4), which means the
behavior is undefined.

In addition, though, this preprocessor token cannot be converted to a
token. The constraint in 6.4p2 is:

Each preprocessing token that is converted to a token shall have
the lexical form of a keyword, an identifier, a constant, a string
literal, or a punctuator.

So, assuming that "\w" isn't surrounded by something like "#if 0"
.... "endif", it would seem to be a constraint violation. By C99
5.1.1.3, this requires a diagnostic even if the behavior is also
undefined.

Note that, by the same reasoning, "abcd\w" should be split into 5
preprocessing tokens:

" abcd \ w "

which just seems confusing. But since such cases require a diagnostic
anyway, a compiler doesn't actually have to pp-tokenize it that way;
as long as it prints a warning or error message, its job is done.

Still, I think the description would have been simpler if a \ followed
by any character in a character or string literal were allowed
syntactically, with a constraint limiting the following character to
the ones that are specified. Then "\w" would be a single pp-token and
a single token (a string literal), with a diagnostic required because
of the constraint violation.

--
Keith Thompson (The_Other_Keit h) kst-u@mib.org <http://www.ghoti.net/~kst>
Nokia
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"

[Antoninus Twink]

Re: C Text/Binary Files

On 23 Jun 2008 at 21:43, Keith Thompson wrote:

䡡牡汤⁶慮 ⁄ij欠㱴牵敤晸䁧 浡楬⹣æ½ã¸ ç²æ¥´æ•³?
㸠佮⁍潮Ⱐ㈳⁊畮′〰 㠠ㄲ㨵㤺〱†〷〰Ⱐä¥æ¥´æ  å‘¨æ½ç³æ½®â· 牯瑥?

You may want to check whether you really mean to include this header:
Content-Type: text/plain; charset=utf-16be