Python throws error when closing /dev/urandom

Thu Oct 22 19:56:00 GMT 2009

2009年10月22日 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.  If you don't read from the file there is no error upon
> closing.
>> $ python
> Python 2.5.2 (r252:60911, Dec  2 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 = open("/dev/urandom")
> .>>> f.close()
>> Note: no problem just opening and closing the special file.  But:
>> .>>> f = open("/dev/urandom")
> .>>> f.read(8)
> '\xf9"\xb7\'E\xf8Q\xa0'
> .>>> f.close()
> Traceback (most recent call last):
>  File "<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 = 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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