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NAME | C SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | SEE ALSO | COLOPHON |
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HANDLE(3) Library Functions Manual HANDLE(3)
path_to_handle, path_to_fshandle, fd_to_handle,
handle_to_fshandle, open_by_handle, readlink_by_handle,
attr_multi_by_handle, attr_list_by_handle, fssetdm_by_handle,
free_handle, getparents_by_handle, getparentpaths_by_handle - file
handle operations
#include <sys/types.h>
#include <xfs/handle.h>
int path_to_handle(char *path, void **hanp, size_t *hlen);
int path_to_fshandle(char *path, void **hanp, size_t *hlen);
int fd_to_handle(int fd, void **hanp, size_t *hlen);
int handle_to_fshandle(void *hanp, size_t hlen, void **fshanp,
size_t *fshlen);
int open_by_handle(void *hanp, size_t hlen, int oflag);
int readlink_by_handle(void *hanp, size_t hlen, void *buf, size_t
bs);
int attr_multi_by_handle(void *hanp, size_t hlen, void *buf, int
rtrvcnt, int flags);
int attr_list_by_handle(void *hanp, size_t hlen, char *buf, size_t
bufsiz, int flags, struct attrlist_cursor *cursor);
int fssetdm_by_handle(void *hanp, size_t hlen, struct fsdmidata
*fssetdm);
void free_handle(void *hanp, size_t hlen);
int getparents_by_handle(void *hanp, size_t hlen, parent_t *buf,
size_t bufsiz, parent_cursor_t *cursor, unsigned int
*count, unsigned int *more);
int getparentpaths_by_handle(void *hanp, size_t hlen, parent_t
*buf, size_t bufsiz, parent_cursor_t *cursor, unsigned int
*count, unsigned int *more);
These functions provide a way to perform certain filesystem
operations without using a file descriptor to access filesystem
objects. They are intended for use by a limited set of system
utilities such as backup programs. They are supported only by the
XFS filesystem. Link with the libhandle library to access these
functions.
A handle, hanp, uniquely identifies a filesystem object or an
entire filesystem. There is one and only one handle per
filesystem or filesystem object. Handles consist of some number
of bytes. The size of a handle (i.e. the number of bytes
comprising it) varies by the type of handle and may vary for
different objects of the same type. The content of a handle is
opaque to applications. Since handle sizes vary and their
contents are opaque, handles are described by two quantities, a
pointer (hanp) and a size (hlen). The size, hlen, indicates the
number of bytes in the handle which are pointed to by the pointer.
The path_to_handle() function returns the handle for the object
given by the path argument. If the final component of the path
name is a symbolic link, the handle returned is that of the link
itself.
The path_to_fshandle() function returns the handle for the
filesystem in which the object given by the path argument resides.
The fd_to_handle() function returns the handle for the object
referenced by the fd argument, which must be a valid file
descriptor.
The handle_to_fshandle() function returns the handle for the
filesystem in which the object referenced by the handle given by
the hanp and hlen arguments resides.
The open_by_handle() function opens a file descriptor for the
object referenced by a handle. It is analogous and identical to
open(2) with the exception of accepting handles instead of path
names.
The readlink_by_handle() function returns the contents of a
symbolic link referenced by a handle.
The attr_multi_by_handle() function manipulates multiple user
attributes on a filesystem object. It is analogous and identical
to attr_multif(3) except that a handle is specified instead of a
file descriptor.
The attr_list_by_handle() function returns the names of the user
attributes of a filesystem object. It is analogous and identical
to attr_listf(3) except that a handle is specified instead of a
file descriptor.
The fssetdm_by_handle() function sets the di_dmevmask and
di_dmstate fields in an XFS on-disk inode. It is analogous to the
XFS_IOC_FSSETDM xfsctl(3) command, except that a handle is
specified instead of a file. This function is not supported on
Linux.
The free_handle() function frees the storage allocated for handles
returned by the following functions: path_to_handle(),
path_to_fshandle(), fd_to_handle(), and handle_to_fshandle().
The getparents_by_handle() function returns an array of parent_t
structures for each hardlink to the inode represented by the given
handle. The parent structure encodes the parent inode number,
generation number and the basename of the link. This function is
not operational on Linux.
The getparentpaths_by_handle() function is identical to the
getparents_by_handle() function except that instead of returning
the basename it returns the path of the link up to the mount
point. This function is also not operational on Linux.
The function free_handle() has no failure indication. The other
functions return the value 0 to the calling process if they
succeed; otherwise, they return the value -1 and set errno to
indicate the error.
EACCES Search permission was denied for a component of path.
EBADF fd is not a valid and open file descriptor.
EFAULT An argument pointed to an invalid address.
EINVAL path is in a filesystem that does not support these
functions.
ELOOP Too many symbolic links were encountered in translating the
path name.
ENAMETOOLONG
A component of path or the entire length of path exceeds
filesystem limits.
ENOENT A component of path does not exist.
EPERM The caller does not have sufficient privileges.
open(2), readlink(2), attr_multi(3), attr_list(3), xfsctl(3),
xfs(5).
This page is part of the xfsprogs (utilities for XFS filesystems)
project. Information about the project can be found at
⟨http://xfs.org/⟩. If you have a bug report for this manual page,
send it to linux-xfs@vger.kernel.org. This page was obtained from
the project's upstream Git repository
⟨https://git.kernel.org/pub/scm/fs/xfs/xfsprogs-dev.git⟩ on
2025-08-11. (At that time, the date of the most recent commit
that was found in the repository was 2025-06-23.) If you discover
any rendering problems in this HTML version of the page, or you
believe there is a better or more up-to-date source for the page,
or you have corrections or improvements to the information in this
COLOPHON (which is not part of the original manual page), send a
mail to man-pages@man7.org
HANDLE(3)
Pages that refer to this page: xfsctl(3), xfs(5)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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