SETATTRLIST(2) BSD System Calls Manual SETATTRLIST(2)
NAME
setattrlist -- set file system attributes
SYNOPSIS
#include <sys/attr.h>
#include <unistd.h>
int
setattrlist(const char* path, struct attrlist * attrList, void * attrBuf, size_t attrBufSize,
unsigned long options);
DESCRIPTION
The setattrlist() function sets attributes (that is, metadata) of file system objects. It is the logi-cal logical
cal opposite of getattrlist(2). The function sets attributes about the file system object specified by
path from the values in the buffer specified by attrBuf and attrBufSize. The attrList parameter deter-mines determines
mines what attributes are set. The options parameter lets you control specific aspects of the func-tion's function's
tion's behaviour.
The 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 vol-umes volumes
umes that don't support setattrlist().
The 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:
ATTR_CMN_GRPID
ATTR_CMN_ACCESSMASK
ATTR_CMN_FLAGS
ATTR_CMN_CRTIME
ATTR_CMN_MODTIME
ATTR_CMN_CHGTIME
ATTR_CMN_ACCTIME
You must be root (that is, your process's effective UID must be 0) in order to change the
ATTR_CMN_OWNERID attribute. Setting other attributes requires that you have write access to the
object.
The attrList parameter is a pointer to an attrlist structure. You are responsible for filling out all
fields of this structure before calling the function. See the discussion of the getattrlist(2) func-tion function
tion for a detailed description of this structure. To set an attribute you must set the corresponding
bit in the appropriate attrgroup_t field of the attrlist structure.
The attrBuf and 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 getattrlist(2) except that,
when setting attributes, the buffer does not include the leading unsigned long length value.
The options parameter is a bit set that controls the behaviour of setattrlist(). The following option
bits are defined.
FSOPT_NOFOLLOW If this bit is set, setattrlist() will not follow a symlink if it occurs as the last
component of path.
RETURN VALUES
Upon successful completion a value of 0 is returned. Otherwise, a value of -1 is returned and errno is
set to indicate the error.
COMPATIBILITY
Not all volumes support setattrlist(). However, if a volume supports getattrlist(2), it must also sup-port support
port setattrlist(). See the documentation for getattrlist(2) for details on how to tell whether a vol-ume volume
ume supports it.
The 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.
If you're implementing a volume format that supports setattrlist(), you should be careful to support
the behaviour specified by this document.
ERRORS
setattrlist() will fail if:
[ENOTSUP] The volume does not support setattrlist().
[ENOTDIR] A component of the path prefix is not a directory.
[ENAMETOOLONG] A component of a path name exceeded NAME_MAX characters, or an entire path name
exceeded PATH_MAX characters.
[ENOENT] The file system object does not exist.
[EROFS] The volume is read-only.
[EACCES] Search permission is denied for a component of the path prefix.
[ELOOP] Too many symbolic links were encountered in translating the pathname.
[EFAULT] path, attrList or attrBuf points to an invalid address.
[EINVAL] The bitmapcount field of attrList is not ATTR_BIT_MAP_COUNT.
[EINVAL] You try to set an invalid attribute.
[EINVAL] You try to set an attribute that is read-only.
[EINVAL] You try to set volume attributes and directory or file attributes at the same time.
[EINVAL] You try to set volume attributes but path does not reference the root of the volume.
[EPERM] You try to set an attribute that can only be set by the owner.
[EACCES] You try to set an attribute that's only settable if you have write permission, and
you do not have write permission.
[EINVAL] The buffer size you specified in attrBufSize is too small to hold all the attributes
that you are trying to set.
[EIO] An I/O error occurred while reading from or writing to the file system.
CAVEATS
If you try to set any volume attributes, you must set ATTR_VOL_INFO in the volattr field, even though
it consumes no data from the attribute buffer.
For more caveats, see also the compatibility notes above.
EXAMPLES
The following code shows how to set the file type and creator of a file by getting the
ATTR_CMN_FNDRINFO attribute using getattrlist(2), modifying the appropriate fields of the 32-byte
Finder information structure, and then setting the attribute back using setattrlist(). This assumes
that the target volume supports the required attributes
#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>
typedef struct attrlist attrlist_t;
struct FInfoAttrBuf {
unsigned long length;
fsobj_type_t objType;
char finderInfo[32];
};
typedef struct FInfoAttrBuf FInfoAttrBuf;
static int FInfoDemo(
const char *path,
const char *type,
const char *creator
)
{
int err;
attrlist_t attrList;
FInfoAttrBuf attrBuf;
assert( strlen(type) == 4 );
assert( strlen(creator) == 4 );
memset(&attrList, 0, sizeof(attrList));
attrList.bitmapcount = ATTR_BIT_MAP_COUNT;
attrList.commonattr = ATTR_CMN_OBJTYPE | ATTR_CMN_FNDRINFO;
err = getattrlist(path, &attrList, &attrBuf, sizeof(attrBuf), 0);
if (err != 0) {
err = errno;
}
if ( (err == 0) && (attrBuf.objType != VREG) ) {
fprintf(stderr, "Not a standard file.\n");
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
);
}
return err;
}
SEE ALSO
chflags(2), chmod(2), chown(2), getattrlist(2), getdirentriesattr(2), searchfs(2), utimes(2)
HISTORY
A setattrlist() function call appeared in Darwin 1.3.1 (Mac OS X version 10.0).
Darwin December 15, 2003 Darwin
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