path: root/man/man3/attr_multi.3

.TH ATTR_MULTI 3 "Extended Attributes" "Dec 2001" "XFS Compatibility API"
.SH NAME
attr_multi, attr_multif \- manipulate multiple user attributes on a filesystem object at once
.SH C SYNOPSIS
.PP
.sp
.nf
.B #include <attr/attributes.h>
.sp
.B "int attr_multi (const char *\f2path\f3, attr_multiop_t *\f2oplist\f3, "
.B "                int \f2count\f3, int \f2flags\f3);"
.PP
.B "int attr_multif (int \f2fd\f3, attr_multiop_t *\f2oplist\f3, "
.B "                 int \f2count\f3, int \f2flags\f3);"
.Op
.SH DESCRIPTION
The
.B attr_multi
and
.B attr_multif
functions provide a way to operate on multiple attributes of a
filesystem object at once.
.P
.I Path
points to a path name for a filesystem object, and 
.I fd
refers to the file descriptor associated with a file.
The 
.I oplist
is an array of \f4attr_multiop_t\fP structures.
Each element in that array describes a single attribute operation
and provides all the information required to carry out that operation
and to check for success or failure of that operation.
.I Count
tells how many elements are in the
.I oplist
array.
.PP
.Op c p a
The contents of an \f4attr_multiop_t\fP structure include
the following members:
.P
.RS 3
.nf
.ft 4
.ta 9n 22n
int am_opcode; /* which operation to perform (see below) */
int am_error; /* [out arg] result of this sub-op (an errno) */
char *am_attrname; /* attribute name to work with */
char *am_attrvalue; /* [in/out arg] attribute value (raw bytes) */
int am_length; /* [in/out arg] length of value */
int am_flags; /* flags (bit-wise OR of #defines below) */
.ft 1
.fi
.RE
.PP
The
.I am_opcode
field defines how the remaining fields are to be interpreted
and can take on one of the following values:
.P
.RS 3
.nf
.ft 4
.ta 9n 22n
ATTR_OP_GET /* return the indicated attr's value */
ATTR_OP_SET /* set/create the indicated attr/value pair */
ATTR_OP_REMOVE /* remove the indicated attr */
.ft 1
.fi
.RE
.PP
The
.I am_error
field will contain the appropriate error result code
if that sub-operation fails.
The result codes for a given sub-operation are a subset of
the result codes that are possible from the corresponding
single-attribute function call.
For example, the result code possible from an \f4ATTR_OP_GET\fP
sub-operation are a subset of those that can be returned from an
.B attr_get
function call.
.PP
The
.I am_attrname
field is a pointer to a NULL terminated string giving the attribute name
that the sub-operation should operate on.
.PP
The
.I am_attrvalue,
.I am_length
and
.I am_flags
fields are used to store the value of the named attribute,
and some control flags for that sub-operation, respectively.
Their use varies depending on the value of the
.I am_opcode
field.
.TP
.SM
.B \%ATTR_OP_GET
The
.I am_attrvalue
field is a pointer to a empty buffer that will be overwritten
with the value of the named attribute.
The
.I am_length
field is initially the total size of the memory buffer that the
.I am_attrvalue
field points to.
After the operation, the
.I am_length
field contains the actual size of the attribute\'s value.
The
.I am_flags
field may be set to the \f4ATTR_ROOT\fP flag.
If the process has appropriate priviledges,
the ROOT namespace will be searched for the named attribute,
otherwise the USER namespace will be searched.
.TP
.SM
.B \%ATTR_OP_SET
The
.I am_attrvalue
and
.I am_length
fields contain the new value for the given attribute name and its length.
The \f4ATTR_ROOT\fP flag may be set in the
.I am_flags
field.
If the process has appropriate priviledges,
the ROOT namespace will be searched for the named attribute,
otherwise the USER namespace will be searched.
The \f4ATTR_CREATE\fP and the \f4ATTR_REPLACE\fP flags
may also be set in the 
.I am_flags
field (but not simultaneously).
If the \f4ATTR_CREATE\fP flag is set,
the sub-operation will set the
.I am_error
field to EEXIST if the named attribute already exists.
If the \f4ATTR_REPLACE\fP flag is set,
the sub-operation will set the
.I am_error
field to ENOATTR if the named attribute does not already exist.
If neither of those two flags are set and the attribute does not exist,
then the attribute will be created with the given value.
If neither of those two flags are set and the attribute already exists,
then the value will be replaced with the given value.
.TP
.SM
.B \%ATTR_OP_REMOVE
The
.I am_attrvalue
and
.I am_length
fields are not used and are ignored.
The
.I am_flags
field may be set to the \f4ATTR_ROOT\fP flag.
If the process has appropriate priviledges,
the ROOT namespace will be searched for the named attribute,
otherwise the USER namespace will be searched.
.PP
The
.I flags
argument to the
.B attr_multi
call is used to control following of symbolic links in the
.I path
argument.
The default is to follow symbolic links,
.I flags
should be set to ATTR_DONTFOLLOW to not follow symbolic links.
.PP
.B attr_multi
will fail if one or more of the following are true:
.TP 17
.SM
\%[ENOENT]
The named file does not exist.
.TP
.SM
\%[EPERM]
The effective user
.SM ID
does not match the owner of the file
and the effective user
.SM ID
is not super-user.
.TP
.SM
\%[ENOTDIR]
A component of the
path prefix
is not a directory.
.TP
.SM
\%[EACCES]
Search permission is denied on a
component of the
path prefix.
.TP
.SM
\%[EINVAL]
A bit other than ATTR_DONTFOLLOW was set in the
.I flag
argument.
.TP
.SM
\%[EFAULT]
.I Path,
or
.I oplist
points outside the allocated address space of the process.
.TP
.SM
\%[ELOOP]
A path name lookup involved too many symbolic links.
.TP
.SM
\%[ENAMETOOLONG]
The length of
.I path
exceeds
.SM
.RI { MAXPATHLEN },
or a pathname component is longer than
.SM
.RI { MAXNAMELEN }.
.PP
.B attr_multif
will fail if:
.TP 15
.SM
\%[EINVAL]
A bit was set in the
.I flag
argument, or
.I fd\^
refers to a socket, not a file.
.TP
.SM
\%[EFAULT]
.I Oplist
points outside the allocated address space of the process.
.TP
.SM
\%[EBADF]
.I Fd\^
does not refer to a valid descriptor.
.SH "DIAGNOSTICS"
Upon successful completion of the
.B attr_multi
call, a value of 0 is returned.
Otherwise, a value of \-1 is returned and
.I errno
is set to indicate the error.
Note that the individual operations listed in the
.I oplist
array each have their own error return fields.
The 
.I errno
variable only records the result of the
.I attr_multi
call itself, not the result of any of the sub-operations.
.SH "SEE ALSO"
.BR attr (1),
.BR attr_get (3),
.BR attr_remove (3),
and
.BR attr_set (3).