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Date: Wed, 7 Jun 2017 11:34:29 +0200
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: question about pread() while reading /dev/sdb
Message-ID: <20170607093429.GC5971@calimero.vinschen.de>
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References: <1d1.g7EO.42ZlNnJjks{.1PDkNn AT seznam DOT cz>
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On Jun  6 19:27, joso AT post DOT cz wrote:
> Hello, I'm porting tool from Linux envirmnment to Windows Cygwin.
> I'm unable to get correct data from pread() while reading /dev/sdx
> On Linux it works as expected, under Cygwin I receive uncorrect data.
>=20
> I have isolated the problem with the following program:
>=20
> #include  stdio.h
> #include  sys/types.h
> #include  sys/stat.h
> #include  fcntl.h
> #include  unistd.h
>=20
> int main(int argc, char *argv[])
> {
>   unsigned char sbuff[512];
>   int f1;
>   f1=3Dopen(argv[1], O_RDWR);
>   pread(f1, sbuff, 512, 0);
>     for(int i=3D0; i 512; i++) printf("%x ",sbuff[i]);
>   close(f1);
> }
>=20
> If the argument is regular file it works. But if the argument is /dev/sdb=
 it does not provide correct data. The shell is run under Administrator per=
mission.
> Thank you for your opinion.

Cygwin's pread is only implemented for regular files at the moment,
for all other objects it returns -1 with errno set to ESPIPE.


Corinna

--=20
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

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