http://qs1969.pair.com?node_id=837072

betterworld has asked for the wisdom of the Perl Monks concerning the following question:

Hi,

according to the Linux man page of fsync(2):

Calling fsync() does not necessarily ensure that the entry in the directory containing the file has also reached disk. For that an explicit fsync() on a file descriptor for the directory is also needed.

So, how do we fsync directories in Perl? perldoc POSIX says that fsync() should be done with the sync method in IO::Handle. So I tried this with a directory:

use IO::Handle; open my $f, '/tmp' or die $!; $f->sync or die "fsync: $!\n";

This bails out with "fsync: Invalid argument". According to strace, no fsync syscall is even tried.

I tried opendir too:

use IO::Handle; my $f = IO::Handle->new; opendir $f, '/tmp' or die $!; $f->sync or die "fsync: $!\n";

with the same result.

On the other hand, an equivalent C program succeeds and properly calls fsync according to strace:

#include <unistd.h> #include <stdlib.h> #include <stdio.h> #include <fcntl.h> #include <sys/types.h> #include <sys/stat.h> int main (void) { int fd = open("/tmp", 0); if (fd < 0) { perror("open: /tmp"); exit(1); } if (fsync(fd) < 0) { perror("fsync: /tmp"); exit(1); } return 0; }

My question: What is the proper way to do fsync with directories in Perl? Or is this just a bug in IO::Handle?

(All tests have been done on a current Debian Squeeze (testing) with perl 5.10.1-12.)