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package Fuse;
use 5.006;
use strict;
use warnings;
use Errno;
use Carp;
use Config;
require Exporter;
require DynaLoader;
use AutoLoader;
use Data::Dumper;
our @ISA = qw(Exporter DynaLoader);
# Items to export into callers namespace by default. Note: do not export
# names by default without a very good reason. Use EXPORT_OK instead.
# Do not simply export all your public functions/methods/constants.
# This allows declaration use Fuse ':all';
# If you do not need this, moving things directly into @EXPORT or @EXPORT_OK
# will save memory.
our %EXPORT_TAGS = (
'all' => [ qw(XATTR_CREATE XATTR_REPLACE fuse_get_context) ],
our @EXPORT_OK = ( @{ $EXPORT_TAGS{'all'} } );
our @EXPORT = ();
our $VERSION = '0.09_2';
# This AUTOLOAD is used to 'autoload' constants from the constant()
# XS function. If a constant is not found then control is passed
# to the AUTOLOAD in AutoLoader.
my $constname;
($constname = $AUTOLOAD) =~ s/.*:://;
croak "& not defined" if $constname eq 'constant';
my $val = constant($constname, @_ ? $_[0] : 0);
if ($! != 0) {
if ($!{EINVAL}) {
goto &AutoLoader::AUTOLOAD;
else {
croak "Your vendor has not defined Fuse macro $constname";
no strict 'refs';
# Fixed between 5.005_53 and 5.005_61
if ($] >= 5.00561) {
*$AUTOLOAD = sub () { $val };
else {
*$AUTOLOAD = sub { $val };
goto &$AUTOLOAD;
# See <sys/xattr.h>.
return 1;
# See <sys/xattr.h>.
return 2;
bootstrap Fuse $VERSION;
sub main {
my @names = qw(getattr readlink getdir mknod mkdir unlink rmdir symlink
rename link chmod chown truncate utime open read write statfs
flush release fsync setxattr getxattr listxattr removexattr);
my @subs = map {undef} @names;
my @validOpts = qw(ro allow_other default_permissions fsname use_ino nonempty);
my $tmp = 0;
my %mapping = map { $_ => $tmp++ } @names;
my %optmap = map { $_ => 1 } @validOpts;
my @otherargs = qw(debug threaded mountpoint mountopts);
my %otherargs = (debug=>0, threaded=>0, mountpoint=>"", mountopts=>"");
while(my $name = shift) {
my ($subref) = shift;
if(exists($otherargs{$name})) {
$otherargs{$name} = $subref;
} else {
croak "There is no function $name" unless exists($mapping{$name});
croak "Usage: Fuse::main(getattr => \"main::my_getattr\", ...)" unless $subref;
$subs[$mapping{$name}] = $subref;
foreach my $opt ( map {m/^([^=]*)/; $1} split(/,/,$otherargs{mountopts}) ) {
next if exists($optmap{$opt});
croak "Fuse::main: invalid '$opt' argument in mountopts";
if($otherargs{threaded}) {
# make sure threads are both available, and loaded.
if($Config{useithreads}) {
if(exists($threads::{VERSION})) {
if(exists($threads::shared::{VERSION})) {
# threads will work.
} else {
carp("Thread support requires you to use threads::shared.\nThreads are disabled.\n");
$otherargs{threaded} = 0;
} else {
carp("Thread support requires you to use threads and threads::shared.\nThreads are disabled.\n");
$otherargs{threaded} = 0;
} else {
carp("Thread support was not compiled into this build of perl.\nThreads are disabled.\n");
$otherargs{threaded} = 0;
# Autoload methods go after =cut, and are processed by the autosplit program.
=head1 NAME
Fuse - write filesystems in Perl using FUSE
use Fuse;
my ($mountpoint) = "";
$mountpoint = shift(@ARGV) if @ARGV;
Fuse::main(mountpoint=>$mountpoint, getattr=>"main::my_getattr", getdir=>"main::my_getdir", ...);
This lets you implement filesystems in perl, through the FUSE
(Filesystem in USErspace) kernel/lib interface.
FUSE expects you to implement callbacks for the various functions.
In the following definitions, "errno" can be 0 (for a success),
-EINVAL, -ENOENT, -EONFIRE, any integer less than 1 really.
You can import standard error constants by saying something like
Every constant you need (file types, open() flags, error values,
etc) can be imported either from POSIX or from Fcntl, often both.
See their respective documentations, for more information.
None by default.
You can request all exportable symbols by using the tag ":all".
You can request the extended attribute symbols by using the tag ":xattr".
This will export XATTR_CREATE and XATTR_REPLACE.
=head3 Fuse::main
Takes arguments in the form of hash key=>value pairs. There are
many valid keys. Most of them correspond with names of callback
functions, as described in section 'FUNCTIONS YOUR FILESYSTEM MAY IMPLEMENT'.
A few special keys also exist:
debug => boolean
=over 1
This turns FUSE call tracing on and off. Default is 0 (which means off).
mountpoint => string
=over 1
The point at which to mount this filesystem. There is no default, you must
specify this. An example would be '/mnt'.
mountopts => string
=over 1
This is a comma seperated list of mount options to pass to the FUSE kernel
At present, it allows the specification of the allow_other
argument when mounting the new FUSE filesystem. To use this, you will also
need 'user_allow_other' in /etc/fuse.conf as per the FUSE documention
mountopts => "allow_other" or
mountopts => ""
threaded => boolean
=over 1
This turns FUSE multithreading on and off. The default is 0, meaning your FUSE
script will run in single-threaded mode. Note that single-threaded mode also
means that you will not have to worry about reentrancy, though you will have to
worry about recursive lookups. In single-threaded mode, FUSE holds a global
lock on your filesystem, and will wait for one callback to return before
calling another. This can lead to deadlocks, if your script makes any attempt
to access files or directories in the filesystem it is providing. (This
includes calling stat() on the mount-point, statfs() calls from the 'df'
command, and so on and so forth.) It is worth paying a little attention and
being careful about this.
Enabling multithreading will cause FUSE to make multiple simultaneous calls
into the various callback functions of your perl script. If you enable
threaded mode, you can enjoy all the parallel execution and interactive
response benefits of threads, and you get to enjoy all the benefits of race
conditions and locking bugs, too. Please also ensure any other perl modules
you're using are also thread-safe.
(If enabled, this option will cause a warning if your perl interpreter was not
built with USE_ITHREADS, or if you have failed to use threads or
=head3 Fuse::fuse_get_context
use Fuse "fuse_get_context";
my $caller_uid = fuse_get_context()->{"uid"};
my $caller_gid = fuse_get_context()->{"gid"};
my $caller_pid = fuse_get_context()->{"pid"};
Access context information about the current Fuse operation.
=head3 getattr
Arguments: filename.
Returns a list, very similar to the 'stat' function (see
perlfunc). On error, simply return a single numeric scalar
value (e.g. "return -ENOENT();").
FIXME: the "ino" field is currently ignored. I tried setting it to 0
in an example script, which consistently caused segfaults.
Fields (the following was stolen from perlfunc(1) with apologies):
= getattr($filename);
Here are the meaning of the fields:
0 dev device number of filesystem
1 ino inode number
2 mode file mode (type and permissions)
3 nlink number of (hard) links to the file
4 uid numeric user ID of file's owner
5 gid numeric group ID of file's owner
6 rdev the device identifier (special files only)
7 size total size of file, in bytes
8 atime last access time in seconds since the epoch
9 mtime last modify time in seconds since the epoch
10 ctime inode change time (NOT creation time!) in seconds
since the epoch
11 blksize preferred block size for file system I/O
12 blocks actual number of blocks allocated
(The epoch was at 00:00 January 1, 1970 GMT.)
=head3 readlink
Arguments: link pathname.
Returns a scalar: either a numeric constant, or a text string.
This is called when dereferencing symbolic links, to learn the target.
example rv: return "/proc/self/fd/stdin";
=head3 getdir
Arguments: Containing directory name.
Returns a list: 0 or more text strings (the filenames), followed by a numeric errno (usually 0).
This is used to obtain directory listings. Its opendir(), readdir(), filldir() and closedir() all in one call.
example rv: return ('.', 'a', 'b', 0);
=head3 mknod
Arguments: Filename, numeric modes, numeric device
Returns an errno (0 upon success, as usual).
This function is called for all non-directory, non-symlink nodes,
not just devices.
=head3 mkdir
Arguments: New directory pathname, numeric modes.
Returns an errno.
Called to create a directory.
=head3 unlink
Arguments: Filename.
Returns an errno.
Called to remove a file, device, or symlink.
=head3 rmdir
Arguments: Pathname.
Returns an errno.
Called to remove a directory.
=head3 symlink
Arguments: Existing filename, symlink name.
Returns an errno.
Called to create a symbolic link.
=head3 rename
Arguments: old filename, new filename.
Returns an errno.
Called to rename a file, and/or move a file from one directory to another.
=head3 link
Arguments: Existing filename, hardlink name.
Returns an errno.
Called to create hard links.
=head3 chmod
Arguments: Pathname, numeric modes.
Returns an errno.
Called to change permissions on a file/directory/device/symlink.
=head3 chown
Arguments: Pathname, numeric uid, numeric gid.
Returns an errno.
Called to change ownership of a file/directory/device/symlink.
=head3 truncate
Arguments: Pathname, numeric offset.
Returns an errno.
Called to truncate a file, at the given offset.
=head3 utime
Arguments: Pathname, numeric actime, numeric modtime.
Returns an errno.
Called to change access/modification times for a file/directory/device/symlink.
=head3 open
Arguments: Pathname, numeric flags (which is an OR-ing of stuff like O_RDONLY
and O_SYNC, constants you can import from POSIX).
Returns an errno.
No creation, or trunctation flags (O_CREAT, O_EXCL, O_TRUNC) will be passed to open().
Your open() method needs only check if the operation is permitted for the given flags, and return 0 for success.
=head3 read
Arguments: Pathname, numeric requestedsize, numeric offset.
Returns a numeric errno, or a string scalar with up to $requestedsize bytes of data.
Called in an attempt to fetch a portion of the file.
=head3 write
Arguments: Pathname, scalar buffer, numeric offset. You can use length($buffer) to
find the buffersize.
Returns an errno.
Called in an attempt to write (or overwrite) a portion of the file. Be prepared because $buffer could contain random binary data with NULLs and all sorts of other wonderful stuff.
=head3 statfs
Arguments: none
Returns any of the following:
$namelen, $files, $files_free, $blocks, $blocks_avail, $blocksize
-ENOANO(), $namelen, $files, $files_free, $blocks, $blocks_avail, $blocksize
=head3 flush
Arguments: Pathname
Returns an errno or 0 on success.
Called to synchronise any cached data. This is called before the file
is closed. It may be called multiple times before a file is closed.
=head3 release
Arguments: Pathname, numeric flags passed to open
Returns an errno or 0 on success.
Called to indicate that there are no more references to the file. Called once
for every file with the same pathname and flags as were passed to open.
=head3 fsync
Arguments: Pathname, numeric flags
Returns an errno or 0 on success.
Called to synchronise the file's contents. If flags is non-zero,
only synchronise the user data. Otherwise synchronise the user and meta data.
=head3 setxattr
Arguments: Pathname, extended attribute's name, extended attribute's value, numeric flags (which is an OR-ing of XATTR_CREATE and XATTR_REPLACE
Returns an errno or 0 on success.
Called to set the value of the named extended attribute.
If you wish to reject setting of a particular form of extended attribute name
(e.g.: regexps matching user\..* or security\..*), then return - EOPNOTSUPP.
If flags is set to XATTR_CREATE and the extended attribute already exists,
this should fail with - EEXIST. If flags is set to XATTR_REPLACE
and the extended attribute doesn't exist, this should fail with - ENOATTR.
XATTR_CREATE and XATTR_REPLACE are provided by this module, but not exported
by default. To import them:
use Fuse ':xattr';
use Fuse ':all';
=head3 getxattr
Arguments: Pathname, extended attribute's name
Returns an errno, 0 if there was no value, or the extended attribute's value.
Called to get the value of the named extended attribute.
=head3 listxattr
Arguments: Pathname
Returns a list: 0 or more text strings (the extended attribute names), followed by a numeric errno (usually 0).
=head3 removexattr
Arguments: Pathname, extended attribute's name
Returns an errno or 0 on success.
=head1 AUTHOR
Mark Glines, E<lt>mark@glines.orgE<gt>
=head1 SEE ALSO
L<perl>, the FUSE documentation.
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