.\" .\" Copyright (c) 2001 Dima Dorfman .\" Copyright (c) 2003 Robert Watson .\" All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" $FreeBSD$ .\" .Dd February 23, 2005 .Dt EXTATTR 2 .Os .Sh NAME .Nm extattr_get_fd , .Nm extattr_set_fd , .Nm extattr_delete_fd , .Nm extattr_list_fd , .Nm extattr_get_file , .Nm extattr_set_file , .Nm extattr_delete_file , .Nm extattr_list_file , .Nm extattr_get_link , .Nm extattr_set_link , .Nm extattr_delete_link , .Nm extattr_list_link .Nd system calls to manipulate VFS extended attributes .Sh LIBRARY .Lb libc .Sh SYNOPSIS .In sys/types.h .In sys/extattr.h .Ft ssize_t .Fn extattr_get_fd "int fd" "int attrnamespace" "const char *attrname" "void *data" "size_t nbytes" .Ft int .Fn extattr_set_fd "int fd" "int attrnamespace" "const char *attrname" "const void *data" "size_t nbytes" .Ft int .Fn extattr_delete_fd "int fd" "int attrnamespace" "const char *attrname" .Ft ssize_t .Fn extattr_list_fd "int fd" "int attrnamespace" "void *data" "size_t nbytes" .Ft ssize_t .Fn extattr_get_file "const char *path" "int attrnamespace" "const char *attrname" "void *data" "size_t nbytes" .Ft int .Fn extattr_set_file "const char *path" "int attrnamespace" "const char *attrname" "const void *data" "size_t nbytes" .Ft int .Fn extattr_delete_file "const char *path" "int attrnamespace" "const char *attrname" .Ft ssize_t .Fn extattr_list_file "const char *path" "int attrnamespace" "void *data" "size_t nbytes" .Ft ssize_t .Fn extattr_get_link "const char *path" "int attrnamespace" "const char *attrname" "void *data" "size_t nbytes" .Ft int .Fn extattr_set_link "const char *path" "int attrnamespace" "const char *attrname" "const void *data" "size_t nbytes" .Ft int .Fn extattr_delete_link "const char *path" "int attrnamespace" "const char *attrname" .Ft ssize_t .Fn extattr_list_link "const char *path" "int attrnamespace" "void *data" "size_t nbytes" .Sh DESCRIPTION Named extended attributes are meta-data associated with vnodes representing files and directories. They exist as .Qq Li name=value pairs within a set of namespaces. .Pp The .Fn extattr_get_file system call retrieves the value of the specified extended attribute into a buffer pointed to by .Fa data of size .Fa nbytes . The .Fn extattr_set_file system call sets the value of the specified extended attribute to the data described by .Fa data . The .Fn extattr_delete_file system call deletes the extended attribute specified. The .Fn 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 .Fn extattr_get_file , and .Fn extattr_list_file calls consume the .Fa data and .Fa nbytes arguments in the style of .Xr read 2 ; .Fn extattr_set_file consumes these arguments in the style of .Xr write 2 . .Pp If .Fa data is .Dv NULL in a call to .Fn 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 .Fn extattr_delete_link , .Fn extattr_get_link , and .Fn extattr_set_link system calls behave in the same way as their _file counterparts, except that they do not follow symlinks. .Pp The .Fn extattr_get_fd , .Fn extattr_set_fd , and .Fn extattr_delete_fd calls are identical to their .Qq Li _file counterparts except for the first argument. The .Qq Li _fd functions take a file descriptor, while the .Qq Li _file functions take a path. Both arguments describe a file associated with the extended attribute that should be manipulated. .Pp The following arguments are common to all the system calls described here: .Bl -tag -width attrnamespace .It Fa attrnamespace the namespace in which the extended attribute resides; see .Xr extattr 9 .It Fa attrname the name of the extended attribute .El .Pp Named extended attribute semantics vary by file system implementing the call. Not all operations may be supported for a particular attribute. Additionally, the format of the data in .Fa data is attribute-specific. .Pp For more information on named extended attributes, please see .Xr extattr 9 . .Sh CAVEAT 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. .Sh RETURN VALUES If successful, the .Fn extattr_get_file and .Fn extattr_set_file calls return the number of bytes that were read or written from the .Fa data , respectively, or if .Fa data was .Dv NULL , then .Fn 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 .Va errno is set to indicate the error. .Pp .Rv -std extattr_delete_file .Sh ERRORS 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. .Bl -tag -width Er .It Bq Er EFAULT The .Fa attrnamespace and .Fa attrname arguments, or the memory range defined by .Fa data and .Fa nbytes point outside the process's allocated address space. .It Bq Er ENAMETOOLONG The attribute name was longer than .Dv EXTATTR_MAXNAMELEN . .El .Pp The .Fn extattr_get_fd , .Fn extattr_set_fd , and .Fn extattr_delete_fd system calls may also fail if: .Bl -tag -width Er .It Bq Er EBADF The file descriptor referenced by .Fa fd was invalid. .El .Pp Additionally, the .Fn extattr_get_file , .Fn extattr_set_file , and .Fn extattr_delete_file calls may also fail due to the following errors: .Bl -tag -width Er .It Bq Er ENOATTR The requested attribute was not defined for this file. .It Bq Er ENOTDIR A component of the path prefix is not a directory. .It Bq Er ENAMETOOLONG A component of a pathname exceeded 255 characters, or an entire path name exceeded 1023 characters. .It Bq Er ENOENT A component of the path name that must exist does not exist. .It Bq Er EACCES Search permission is denied for a component of the path prefix. .\" XXX are any missing? .El .Sh SEE ALSO .Xr extattr 3 , .Xr getextattr 8 , .Xr setextattr 8 , .Xr extattr 9 , .Xr VOP_GETEXTATTR 9 , .Xr VOP_SETEXTATTR 9 .Sh HISTORY Extended attribute support was developed as part of the .Tn TrustedBSD Project, and introduced in .Fx 5.0 . It was developed to support security extensions requiring additional labels to be associated with each file or directory. .Sh BUGS In earlier versions of this API, passing an empty string for the attribute name to .Fn extattr_get_fd , .Fn extattr_get_file , or .Fn extattr_get_link would return the list of attributes defined for the target object. This interface has been deprecated in preference to using the explicit list API, and should not be used.