G'day Rick,

As far as I can tell, Sys::Filesystem does not report what fstab file it uses. It relies on the various Sys::Filesystem::<OS> modules, e.g. Sys::Filesystem::AIX, for the filesystem information. See the "Sys-Filesystem distro page" for a list of those modules.

If you simply want to perform some upfront sanity checks, perhaps code similar to the following might suffice.

#!/usr/bin/env perl

use 5.010;
use strict;
use warnings;

use Sys::Filesystem ();

if (Sys::Filesystem::->supported()) {
    my $fs = Sys::Filesystem::->new();

    say '$Sys::Filesystem::FSTAB: ',
            $Sys::Filesystem::FSTAB // 'undefined';
    say '$fs->{fstab}: ', $fs->{fstab} // 'undefined';
    say "O/S '$^O' supported.";
    say 'Using: ', ref($fs->{filesystems});
    my @fs_list = $fs->filesystems();

    if (@fs_list) {
        say 'Filesystems found:';
        say "\t$_" for @fs_list;
    }
    else {
        warn "No filesystems found.\n";
    }

    use Data::Dump;
    say '=' x 60;
    say 'Sys::Filesystem Object:';
    say '=' x 60;
    dd $fs;
    say '-' x 60;
}
else {
    warn "O/S '$^O' not supported.\n";
}
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I've included code to produce a lot of additional information which you may find interesting, but probably isn't wanted in production.

I'm strongly against breaking encapsulation and urge you to stick with the published API. I only included $fs->{fstab} and $fs->{filesystems} for demonstration purposes.

I don't have any of the four OSes you list available at home. Here's the output on my Cygwin system.

$Sys::Filesystem::FSTAB: undefined
$fs->{fstab}: undefined
O/S 'cygwin' supported.
Using: Sys::Filesystem::Cygwin
Filesystems found:
        /
        /cygdrive/c
        /cygdrive/d
        /usr/bin
        /usr/lib
============================================================
Sys::Filesystem Object:
============================================================
bless({
  aliases     => {
                   boot_order      => ["fs_mntno"],
                   check_frequency => ["fs_freq"],
                   check_order     => ["fs_passno"],
                   device          => ["fs_spec", "dev"],
                   filesystem      => ["fs_file", "mount_point"],
                   format          => ["fs_vfstype", "vfs", "vfstype"]
+,
                   label           => ["fs_label"],
                   mount_point     => ["fs_file", "filesystem"],
                   options         => ["fs_mntops"],
                   type            => ["fs_vfstype", "vfs"],
                   volume          => ["fs_volume", "fs_vol", "vol"],
                 },
  canondev    => undef,
  filesystems => bless({
                   "/" => {
                     device      => "C:/cygwin64",
                     fs_file     => "/",
                     fs_mntops   => "binary,auto",
                     fs_spec     => "C:/cygwin64",
                     fs_vfstype  => "ntfs",
                     mount_point => "/",
                     mounted     => 1,
                   },
                   "/cygdrive/c" => {
                     device      => "C:",
                     fs_file     => "/cygdrive/c",
                     fs_mntops   => "binary,posix=0,user,noumount,auto
+",
                     fs_spec     => "C:",
                     fs_vfstype  => "ntfs",
                     mount_point => "/cygdrive/c",
                     mounted     => 1,
                   },
                   "/cygdrive/d" => {
                     device      => "D:",
                     fs_file     => "/cygdrive/d",
                     fs_mntops   => "binary,posix=0,user,noumount,auto
+",
                     fs_spec     => "D:",
                     fs_vfstype  => "ntfs",
                     mount_point => "/cygdrive/d",
                     mounted     => 1,
                   },
                   "/usr/bin" => {
                     device      => "C:/cygwin64/bin",
                     fs_file     => "/usr/bin",
                     fs_mntops   => "binary,auto",
                     fs_spec     => "C:/cygwin64/bin",
                     fs_vfstype  => "ntfs",
                     mount_point => "/usr/bin",
                     mounted     => 1,
                   },
                   "/usr/lib" => {
                     device      => "C:/cygwin64/lib",
                     fs_file     => "/usr/lib",
                     fs_mntops   => "binary,auto",
                     fs_spec     => "C:/cygwin64/lib",
                     fs_vfstype  => "ntfs",
                     mount_point => "/usr/lib",
                     mounted     => 1,
                   },
                 }, "Sys::Filesystem::Cygwin"),
  fstab       => undef,
  mtab        => undef,
}, "Sys::Filesystem")
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