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Date: Thu, 22 Oct 2009 20:55:57 +0100
Message-ID: <416096c60910221255i550948a1n10301cd417e9f5cd@mail.gmail.com>
Subject: Re: Python throws error when closing /dev/urandom
From: Andy Koppe <andy DOT koppe AT gmail DOT com>
To: cygwin AT cygwin DOT com
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2009/10/22 Topher Cawlfield
> I'm not sure if this is the right place to post such problems, but I ran =
into
> this problem when trying to use the paramiko library with python 2.5.2 in=
 Cygwin.
>
> Ultimately the problem is that an IOError is generated when opening
> /dev/urandom, reading some bytes from it (doesn't seem to matter how much=
),
> and closing the file. =C2=A0If you don't read from the file there is no e=
rror upon
> closing.
>
> $ python
> Python 2.5.2 (r252:60911, Dec =C2=A02 2008, 09:26:14)
> [GCC 3.4.4 (cygming special, gdc 0.12, using dmd 0.125)] on cygwin
> Type "help", "copyright", "credits" or "license" for more information.
> .>>> f =3D open("/dev/urandom")
> .>>> f.close()
>
> Note: no problem just opening and closing the special file. =C2=A0But:
>
> .>>> f =3D open("/dev/urandom")
> .>>> f.read(8)
> '\xf9"\xb7\'E\xf8Q\xa0'
> .>>> f.close()
> Traceback (most recent call last):
> =C2=A0File "<stdin>", line 1, in <module>
> IOError: [Errno 0] Error
> .>>>

Reproduced the issue with this C test:

#include <stdlib.h>
#include <stdio.h>

int main(void) {
  FILE *f =3D fopen("/dev/urandom", "r");
  if (!f) {
    puts("fopen failed");
    return 1;
  }
  char buf[8];
  printf("read %i bytes\n", fread(buf, 1, sizeof buf, f));
  if (fclose(f)) {
    puts("fclose failed");
    return 1;
  }
  return 0;
}

The fclose fails on Cygwin, but succeeds on Debian.

Andy

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