EXTATTR_GET_FILE(2) BSD System Calls Manual EXTATTR_GET_FILE(2)
extattr_get_fd, extattr_set_fd, extattr_delete_fd, extattr_list_fd, extattr_get_file,
extattr_set_file, extattr_delete_file, extattr_list_file, extattr_get_link,
extattr_set_link, extattr_delete_link, extattr_list_link -- system calls to manipulate VFS
Standard C Library (libc, -lc)
extattr_get_fd(int fd, int attrnamespace, const char *attrname, void *data, size_t nbytes);
extattr_set_fd(int fd, int attrnamespace, const char *attrname, const void *data,
extattr_delete_fd(int fd, int attrnamespace, const char *attrname);
extattr_list_fd(int fd, int attrnamespace, void *data, size_t nbytes);
extattr_get_file(const char *path, int attrnamespace, const char *attrname, void *data,
extattr_set_file(const char *path, int attrnamespace, const char *attrname,
const void *data, size_t nbytes);
extattr_delete_file(const char *path, int attrnamespace, const char *attrname);
extattr_list_file(const char *path, int attrnamespace, void *data, size_t nbytes);
extattr_get_link(const char *path, int attrnamespace, const char *attrname, void *data,
extattr_set_link(const char *path, int attrnamespace, const char *attrname,
const void *data, size_t nbytes);
extattr_delete_link(const char *path, int attrnamespace, const char *attrname);
extattr_list_link(const char *path, int attrnamespace, void *data, size_t nbytes);
Named extended attributes are meta-data associated with vnodes representing files and direc-
tories. They exist as "name=value" pairs within a set of namespaces.
The extattr_get_file() system call retrieves the value of the specified extended attribute
into a buffer pointed to by data of size nbytes. The extattr_set_file() system call sets
the value of the specified extended attribute to the data described by data. The
extattr_delete_file() system call deletes the extended attribute specified. The
extattr_list_file() returns a list of attributes present in the requested namespace. Each
list entry consists of a single byte containing the length of the attribute name, followed
by the attribute name. The attribute name is not terminated by ASCII 0 (nul). The
extattr_get_file() and extattr_list_file() calls consume the data and nbytes arguments in
the style of read(2); extattr_set_file() consumes these arguments in the style of write(2).
If data is NULL in a call to extattr_get_file() then the size of defined extended attribute
data will be returned, rather than the quantity read, permitting applications to test the
size of the data without performing a read.
The extattr_delete_link(), extattr_get_link(), and extattr_set_link() system calls behave in
the same way as their _file counterparts, except that they do not follow symlinks.
The extattr_get_fd(), extattr_set_fd(), and extattr_delete_fd() calls are identical to their
"_file" counterparts except for the first argument. The "_fd" functions take a file
descriptor, while the "_file" functions take a path. Both arguments describe a file associ-
ated with the extended attribute that should be manipulated.
The following arguments are common to all the system calls described here:
attrnamespace the namespace in which the extended attribute resides; see extattr(9)
attrname the name of the extended attribute
Named extended attribute semantics vary by file system implementing the call. Not all oper-
ations may be supported for a particular attribute. Additionally, the format of the data in
data is attribute-specific.
For more information on named extended attributes, please see extattr(9).
If successful, the extattr_get_file() and extattr_set_file() calls return the number of
bytes that were read or written from the data, respectively, or if data was NULL, then
extattr_get_file() returns the number of bytes available to read. If any of the calls are
unsuccessful, the value -1 is returned and the global variable errno is set to indicate the
The extattr_delete_file() function returns the value 0 if successful; otherwise the value -1
is returned and the global variable errno is set to indicate the error.
The following errors may be returned by the system calls themselves. Additionally, the file
system implementing the call may return any other errors it desires.
[EFAULT] The attrnamespace and attrname arguments, or the memory range defined by
data and nbytes point outside the process's allocated address space.
[ENAMETOOLONG] The attribute name was longer than EXTATTR_MAXNAMELEN.
The extattr_get_fd(), extattr_set_fd(), and extattr_delete_fd() system calls may also fail
[EBADF] The file descriptor referenced by fd was invalid.
Additionally, the extattr_get_file(), extattr_set_file(), and extattr_delete_file() calls
may also fail due to the following errors:
[EACCES] Search permission is denied for a component of the path prefix.
[ENAMETOOLONG] A component of a pathname exceeded 255 characters, or an entire path name
exceeded 1023 characters.
[ENOENT] A component of the path name that must exist does not exist.
[ENOTDIR] A component of the path prefix is not a directory.
getextattr(1), extattr(3), extattr(9)
Extended attribute support was developed as part of the TrustedBSD Project, and introduced
in FreeBSD 5.0 and NetBSD 3.0. It was developed to support security extensions requiring
additional labels to be associated with each file or directory.
This interface is under active development, and as such is subject to change as applications
are adapted to use it. Developers are discouraged from relying on its stability.
Note that previous versions of this man page incorrectly stated that extattr_list_file()
returned a list of attribute names separated by ASCII 0 (nul).
BSD August 3, 2011 BSD