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[apple/xnu.git] / bsd / man / man2 / setattrlist.2

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.\" 
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.\" License for the specific language governing rights and limitations
.\" under the License.
.\" 
.\"     @(#)setattrlist.2
.
.Dd December 15, 2003
.Dt SETATTRLIST 2
.Os Darwin
.Sh NAME
.Nm setattrlist
.Nd set file system attributes
.Sh SYNOPSIS
.Fd #include <sys/attr.h>
.Fd #include <unistd.h>
.Ft int
.Fn setattrlist "const char* path" "struct attrlist * attrList" "void * attrBuf" "size_t attrBufSize" "unsigned long options"
.
.Sh DESCRIPTION
The
.Fn setattrlist
function sets attributes (that is, metadata) of file system objects.
It is the logical opposite of 
.Xr getattrlist 2 .
The function sets attributes about the file system object specified by 
.Fa path
from the values in the buffer specified by 
.Fa attrBuf
and
.Fa attrBufSize .
The 
.Fa attrList 
parameter determines what attributes are set. 
The 
.Fa options 
parameter lets you control specific aspects of the function's behaviour.
.Pp
.
The 
.Fn setattrlist 
function is only supported by certain volume format implementations. 
For maximum compatibility, client programs should use high-level APIs 
(such as the Carbon File Manager) to access file system attributes.
These high-level APIs include logic to emulate file system attributes 
on volumes that don't support 
.Fn setattrlist .
.Pp
.
.\" path parameter
.
The
.Fa path
parameter must reference a valid file system object.
All directories listed in the path name leading to the object 
must be searchable.
You must own the file system object in order to set any of the 
following attributes: 
.Pp
.
.Bl -item -compact
.It
ATTR_CMN_GRPID
.It
ATTR_CMN_ACCESSMASK
.It
ATTR_CMN_FLAGS
.It
ATTR_CMN_CRTIME
.It
ATTR_CMN_MODTIME
.It
ATTR_CMN_CHGTIME
.It
ATTR_CMN_ACCTIME
.El
.Pp
.
You must be root (that is, your process's effective UID must be 0) in order to change the 
.Dv ATTR_CMN_OWNERID
attribute.
Setting other attributes requires that you have write access to the object.
.Pp
.
.\" attrList parameter
.
The
.Fa attrList
parameter is a pointer to an 
.Vt attrlist 
structure. 
You are responsible for filling out all fields of this structure before calling the function. 
See the discussion of the  
.Xr getattrlist 2 
function for a detailed description of this structure. 
To set an attribute you must set the corresponding bit in the appropriate 
.Vt attrgroup_t 
field of the 
.Vt attrlist 
structure.
.Pp
.
.\" attrBuf and attrBufSize parameters
.
The
.Fa attrBuf
and 
.Fa attrBufSize
parameters specify a buffer that contains the attribute values to set. 
Attributes are packed in exactly the same way as they are returned from 
.Xr getattrlist 2 
except that, when setting attributes, the buffer does not include the leading 
.Vt unsigned long 
length value.
.Pp
.
.\" option parameter
.
The
.Fa options
parameter is a bit set that controls the behaviour of
.Fn setattrlist .
The following option bits are defined.
.
.Bl -tag -width XXXbitmapcount
.
.It FSOPT_NOFOLLOW
If this bit is set, 
.Fn setattrlist 
will not follow a symlink if it occurs as 
the last component of
.Fa path .
.
.El
.
.Sh RETURN VALUES
Upon successful completion a value of 0 is returned.
Otherwise, a value of -1 is returned and
.Va errno
is set to indicate the error.
.
.Sh COMPATIBILITY
Not all volumes support 
.Fn setattrlist .
However, if a volume supports 
.Xr getattrlist 2 ,
it must also support 
.Fn setattrlist .
See the documentation for 
.Xr getattrlist 2 
for details on how to tell whether a volume supports it.
.Pp
.
The 
.Fn setattrlist 
function has been undocumented for more than two years. 
In that time a number of volume format implementations have been created without 
a proper specification for the behaviour of this routine. 
You may encounter volume format implementations with slightly different 
behaviour than what is described here. 
Your program is expected to be tolerant of this variant behaviour.
.Pp
.
If you're implementing a volume format that supports 
.Fn setattrlist ,
you should be careful to support the behaviour specified by this document.
.
.Sh ERRORS
.Fn setattrlist
will fail if:
.Bl -tag -width Er
.
.It Bq Er ENOTSUP
The volume does not support
.Fn setattrlist .
.
.It Bq Er ENOTDIR
A component of the path prefix is not a directory.
.
.It Bq Er ENAMETOOLONG
A component of a path name exceeded 
.Dv NAME_MAX
characters, or an entire path name exceeded 
.Dv PATH_MAX
characters.
.
.It Bq Er ENOENT
The file system object does not exist.
.
.It Bq Er EROFS
The volume is read-only.
.
.It Bq Er EACCES
Search permission is denied for a component of the path prefix.
.
.It Bq Er ELOOP
Too many symbolic links were encountered in translating the pathname.
.
.It Bq Er EFAULT
.Fa path ,
.Fa attrList
or
.Em attrBuf
points to an invalid address.
.
.It Bq Er EINVAL
The 
.Fa bitmapcount 
field of 
.Fa attrList 
is not 
.Dv ATTR_BIT_MAP_COUNT .
.
.It Bq Er EINVAL
You try to set an invalid attribute.
.
.It Bq Er EINVAL
You try to set an attribute that is read-only.
.
.It Bq Er EINVAL
You try to set volume attributes and directory or file attributes at the same time.
.
.It Bq Er EINVAL
You try to set volume attributes but 
.Fa path 
does not reference the root of the volume.
.
.It Bq Er EPERM
You try to set an attribute that can only be set by the owner.
.
.It Bq Er EACCES
You try to set an attribute that's only settable if you have write permission, 
and you do not have write permission.
.
.It Bq Er EINVAL
The buffer size you specified in 
.Fa attrBufSize 
is too small to hold all the attributes that you are trying to set.
.
.It Bq Er EIO
An I/O error occurred while reading from or writing to the file system.
.El
.Pp
.
.Sh CAVEATS
.
If you try to set any volume attributes, you must set 
.Dv ATTR_VOL_INFO 
in the 
.Fa volattr
field, even though it consumes no data from the attribute buffer.
.Pp
.
For more caveats, see also the compatibility notes above.
.
.Sh EXAMPLES
.
The following code shows how to set the file type and creator of 
a file by getting the 
.Dv ATTR_CMN_FNDRINFO 
attribute using 
.Xr getattrlist 2 , 
modifying the appropriate fields of the 32-byte Finder information structure, 
and then setting the attribute back using 
.Fn setattrlist . 
This assumes that the target volume supports the required attributes
.
.Bd -literal
#include <assert.h>
#include <stdio.h>
#include <stddef.h>
#include <string.h>
#include <sys/attr.h>
#include <sys/errno.h>
#include <unistd.h>
#include <sys/vnode.h>
.Pp
.
typedef struct attrlist attrlist_t;
.Pp
.
struct FInfoAttrBuf 
    unsigned long   length;
    fsobj_type_t    objType;
    char            finderInfo[32];
};
typedef struct FInfoAttrBuf FInfoAttrBuf;
.Pp
.
static int FInfoDemo(
    const char *path, 
    const char *type, 
    const char *creator
)
{
    int             err;
    attrlist_t      attrList;
    FInfoAttrBuf    attrBuf;
.Pp
    
    assert( strlen(type)    == 4 );
    assert( strlen(creator) == 4 );
.Pp
.
    memset(&attrList, 0, sizeof(attrList));
    attrList.bitmapcount = ATTR_BIT_MAP_COUNT;
    attrList.commonattr  = ATTR_CMN_OBJTYPE | ATTR_CMN_FNDRINFO;
.Pp
    
    err = getattrlist(path, &attrList, &attrBuf, sizeof(attrBuf), 0);
    if (err != 0) {
        err = errno;
    }
.Pp
    
    if ( (err == 0) && (attrBuf.objType != VREG) ) {
        fprintf(stderr, "Not a standard file.\en");
        err = EINVAL;
    } else {
        memcpy( &attrBuf.finderInfo[0], type,    4 );
        memcpy( &attrBuf.finderInfo[4], creator, 4 );
        
        attrList.commonattr = ATTR_CMN_FNDRINFO;
        err = setattrlist(
            path, 
            &attrList, 
            attrBuf.finderInfo, 
            sizeof(attrBuf.finderInfo), 
            0
        );
    }
.Pp
    return err;
}
.Ed
.Pp
.
.Sh SEE ALSO
.
.Xr chflags 2 ,
.Xr chmod 2 ,
.Xr chown 2 ,
.Xr getattrlist 2 ,
.Xr getdirentriesattr 2 ,
.Xr searchfs 2 ,
.Xr utimes 2
.
.Sh HISTORY
A
.Fn setattrlist
function call appeared in Darwin 1.3.1 (Mac OS X version 10.0).
.