On 02/09/2015 01:53 PM, Eric Blake wrote: > On 02/09/2015 01:38 PM, Thomas Wolff wrote: > >>> bash prints that message when it has the noclobber-option set. Maybe >>> you check it? >> Yes, indeed, the effect shows up after set -o noclobber; >> however, this shouldn’t apply to device files (and doesn’t on other >> systems) - >> man bash: “redirection will fail if the file ... is a regular file.” > > Huh. I can reproduce it, even with the new experimental bash 4.3. I'll > see if I can find the bug in the sources.
The bug is in cygwin1.dll, not bash. Here's a STC; opening a file
should NOT change its st_ino number, but that's exactly what cygwin is
doing to /dev/tty. As such, bash thinks that because the ino changed
between stat() and open() that there is a race of someone trying to do
bad things behind bash's back, and noclobber restrictions kick in to
prevent bash from using the file.
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/stat.h>
int main(void) {
struct stat st1, st2;
if (stat"/dev/tty", &st1))
return 1;
int fd = open("/dev/tty", O_CREAT|O_WRONLY, 0666);
if (fd < 0)
return 2;
if (fstat(fd, &st2))
return 3;
printf ("%lld %c= %lld\n", (long long) st1.st_ino,
st1.st_ino == st2.st_ino ? '=' : '!',
(long long) st2.st_ino);
return 0;
}
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
signature.asc
Description: OpenPGP digital signature
