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Date: Sat, 27 Mar 2021 17:02:13 +0300
Message-Id: <83o8f4oftm.fsf@gnu.org>
From: "Eli Zaretskii (eliz AT gnu DOT org) [via djgpp AT delorie DOT com]" <djgpp AT delorie DOT com>
To: djgpp AT delorie DOT com
In-Reply-To:
	<CAA2C=vDMw+wQsbxDkYcXsPgdqeUMDNwz7-NCujx+G11M1vpmzg AT mail DOT gmail DOT com>
	(djgpp AT delorie DOT com)
Subject: Re: issue with popen and reading from stdout
References: <CAA2C=vDMw+wQsbxDkYcXsPgdqeUMDNwz7-NCujx+G11M1vpmzg AT mail DOT gmail DOT com>
Reply-To: djgpp AT delorie DOT com

> From: "Ozkan Sezer (sezeroz AT gmail DOT com) [via djgpp AT delorie DOT com]" <djgpp AT delorie DOT com>
> Date: Sat, 27 Mar 2021 16:39:08 +0300
> 
> The code is basically:
> 
> p = popen(cmdline, "rb");
> while ((n = fread(buf, 1, BUFLEN, p)) > 0) {
>     fwrite(buf, 1, n, t);
> }
> pclose(p);
> 
> ... where cmdline is like "unrar p -inul ponylips.rar".  The "p" makes
> unrar to extract to stdout, -inul makes unrar to emit no messages.
> 
> The issue is:  Whatever I do, including inserting calls like
> setmode(fileno(stdout),O_BINARY), extracted file has 0x0a -> 0x0d 0x0a
> changes and corrupted.  For what it's worth, manually running that cmd
> on the console itself, like "unrar p -inul ponylips.rar > ponylips.mod"
> gives the same result.

I don't think I understand what you mean by "extracted file has 0x0a
 -> 0x0d 0x0a changes and corrupted".

The above program's expected effect is to read what "unrar -p" emits
without any EOL conversions.  Programs that run on MS-DOS/Windows
usually output CRLF end-of-line sequences (i.e. 0x0d + 0x0a), so the
program you show should:

 . read these CRLF EOLs without any conversion
 . write each line to stdout

Whether 'fwrite' add another 0x0d to each line depends on the mode of
the stream 't'; if you open it in binary mode, I would expect to see
the same CRLF EOLs as what "unrar -p" emits.  If 't' is in text mode,
you will see each line end with 0x0d 0x0d 0x0a, i.e. 2 CR characters
followed by a single newline.