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NAME | C SYNOPSIS | DESCRIPTION | DIAGNOSTICS | SEE ALSO | COLOPHON |
ATTR_LIST(3) XFS Compatibility API ATTR_LIST(3)
attr_list, attr_listf - list the names of the user attributes of a
filesystem object
#include <sys/attributes.h>
int attr_list (const char ∗path, char ∗buffer,
const int buffersize, int flags,
attrlist_cursor_t ∗cursor);
int attr_listf (int fd, char ∗buffer,
const int buffersize, int flags,
attrlist_cursor_t ∗cursor);
The attr_list and attr_listf functions provide a way to list the
existing attributes of a filesystem object.
Path points to a path name for a filesystem object, and fd refers to
the file descriptor associated with a file. The buffer will be
filled with a structure describing at least a portion of the
attributes associated with the given filesystem object. Buffer will
be overwritten with an attrlist_t structure containing a list of the
attributes associated with that filesystem object, up to a maximum of
buffersize bytes. The buffer must be sufficiently large to hold the
appropriate data structures plus at least one maximally sized
attribute name, but cannot be more than ATTR_MAX_VALUELEN (currently
64KB) bytes in length.
The contents of an attrlist_t structure include the following
members:
int32_t al_count; /∗ number of entries in attrlist ∗/
int32_t al_more; /∗ T/F: more attrs (do syscall again) ∗/
int32_t al_offset[1]; /∗ byte offsets of attrs [var-sized] ∗/
The al_count field shows the number of attributes represented in this
buffer, which is also the number of elements in the al_offset array.
The al_more field will be non-zero if another attr_list call would
result in more attributes. The al_offset array contains the byte
offset within the buffer of the structure describing each of the
attributes, an attrlist_ent_t structure. The ATTR_ENTRY(buffer,
index) macro will help with decoding the list. It takes a pointer to
the buffer and an index into the al_offset array and returns a
pointer to the corresponding attrlist_ent_t structure.
The contents of an attrlist_ent_t structure include the following
members:
uint32_t a_valuelen; /∗ number bytes in value of attr ∗/
char a_name[]; /∗ attr name (NULL terminated) ∗/
The a_valuelen field shows the size in bytes of the value associated
with the attribute whose name is stored in the a_name field. The
name is a NULL terminated string.
Note that the value of the attribute cannot be obtained through this
interface, the attr_get call should be used to get the value. The
attr_list interface tells the calling process how large of a buffer
it must have in order to get the attribute´s value.
The flags argument can contain the following symbols bitwise OR´ed
together:
ATTR_ROOT
List the attributes that are in the root address space, not in
the user address space. (limited to use by super-user only)
ATTR_DONTFOLLOW
Do not follow symbolic links when resolving a path on an
attr_list function call. The default is to follow symbolic
links.
The cursor argument is a pointer to an opaque data structure that the
kernel uses to track the calling process´s position in the attribute
list. The only valid operations on a cursor are to pass it into an
attr_list function call or to zero it out. It should be zero´ed out
before the first attr_list call. Note that multi-threaded
applications may keep more than one cursor in order to serve multiple
contexts, ie: the attr_list call is "thread-safe".
attr_list will fail if one or more of the following are true:
[ENOENT] The named file does not exist.
[EPERM] The effective user ID does not match the owner of
the file and the effective user ID is not super-
user.
[ENOTDIR] A component of the path prefix is not a directory.
[EACCES] Search permission is denied on a component of the
path prefix.
[EINVAL] A bit was set in the flag argument that is not
defined for this system call, or the buffer was too
small or too large.
[EFAULT] Either Path or buffer points outside the allocated
address space of the process, or buffer or bufsize
are not 32bit aligned.
[ELOOP] A path name lookup involved too many symbolic links.
[ENAMETOOLONG] The length of path exceeds {MAXPATHLEN}, or a
pathname component is longer than {MAXNAMELEN}.
[ENOATTR] attribute does not exist for this file.
attr_listf will fail if:
[EINVAL] A bit was set in the flag argument that is not defined
for this system call, or fd refers to a socket, not a
file, or the buffer was too small or too large.
[EFAULT] Either Path or buffer points outside the allocated
address space of the process, or buffer or bufsize are
not 32bit aligned.
[EBADF] Fd does not refer to a valid descriptor.
Upon successful completion, a value of 0 is returned. Otherwise, a
value of -1 is returned and errno is set to indicate the error.
attr(1), attr_multi(3), attr_remove(3), and attr_set(3).
This page is part of the attr (manipulating filesystem extended
attributes) project. Information about the project can be found at
⟨http://savannah.nongnu.org/projects/attr⟩. If you have a bug report
for this manual page, see
⟨http://savannah.nongnu.org/bugs/?group=attr⟩. This page was obtained
from the project's upstream Git repository
⟨git://git.savannah.nongnu.org/attr.git⟩ on 2017-07-05. If you dis‐
cover 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
Dec 2005 Extended Attributes ATTR_LIST(3)
Pages that refer to this page: attr_get(3), attr_multi(3), attr_remove(3), attr_set(3), handle(3)