Under Unix-like systems, sometimes checking the device field returned by lstat() will work. For instance, here's the wanted() routine generated by find2perl / -xdev: 
use File::Find;

File::Find::find({wanted => \&wanted}, '/');
exit;

sub wanted {
    my ($dev,$ino,$mode,$nlink,$uid,$gid);

    (($dev,$ino,$mode,$nlink,$uid,$gid) = lstat($_)) &&
    !($File::Find::prune |= ($dev != $File::Find::topdev))
    && print("$name\n");
}

[download]
$File::Find::topdev is simply the device associated with the root directory /: 
($File::Find::topdev) = lstat("/");

[download]

In reply to Re: How to determine if a file is a mount point? by pc88mxer
in thread How to determine if a file is a mount point? by gw1500se

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