SETATTRLIST(2) System Calls Manual SETATTRLIST(2)

setattrlist, fsetattrlist, setattrlistat — set file system attributes

#include <sys/attr.h>
#include <unistd.h>

int
setattrlist(const char * path, struct attrlist * attrList, void * attrBuf, size_t attrBufSize, unsigned long options);

int
fsetattrlist(int fd, struct attrlist * attrList, void * attrBuf, size_t attrBufSize, unsigned long options);

int
setattrlistat(int dir_fd, const char * path, struct attrlist * attrList, void * attrBuf, size_t attrBufSize, uint32_t options);

The () and () functions set attributes (that is, metadata) of file system objects. They are the logical opposite of getattrlist(2). The setattrlist() function sets attributes about the file system object specified by path from the values in the buffer specified by attrBuf and attrBufSize; the fsetattrlist() function does the same for the fd file descriptor. The attrList parameter determines what attributes are set. The options parameter lets you control specific aspects of the function's behaviour.

The () system call is equivalent to setattrlist() except in the case where path specifies a relative path. In this case the attributes are set for the file system object named by path relative to the directory associated with the file descriptor fd instead of the current working directory. If setattrlistat() is passed the special value AT_FDCWD in the fd parameter, the current working directory is used and the behavior is identical to a call to setattrlist().

The functions are 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 () and ().

The path parameter for () must reference a valid file system object. All directories listed in the path name leading to the object must be searchable. The fd parameter for () must be a valid file descriptor for the calling process. The list of potentially settable attributes via setattrlist() is different than the list of attributes that are accessible via () In particular, only the following attributes are modifiable via setattrlist() and not all of them may be supported on all filesystems.

You must own the file system object in order to set any of the following attributes:

If ATTR_CMN_MODTIME is set to a time before ATTR_CMN_CRTIME, the value of ATTR_CMN_CRTIME is set to the same value as ATTR_CMN_MODTIME.

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) function 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 u_int32_t length value.

The options parameter is a bit set that controls the behaviour of (). 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.
FSOPT_NOFOLLOW_ANY
If this bit is set, setattrlist() will not follow a symlink if it occurs as the last component of path. In addition, if a symbolic link is encountered before the final component, an error is returned

Upon successful completion a value of 0 is returned. Otherwise, a value of -1 is returned and errno is set to indicate the error.

Not all volumes support setattrlist(). However, if a volume supports getattrlist(2), it must also support setattrlist(). See the documentation for getattrlist(2) for details on how to tell whether a volume 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.

setattrlist() and fsetattrlist() will fail if:

[]
The call is not supported by the volume.
[]
A component of the path for setattrlist() prefix is not a directory.
[]
A component of a path name for setattrlist() exceeded NAME_MAX characters, or an entire path name exceeded PATH_MAX characters.
[]
The file system object for setattrlist() does not exist.
[]
The file descriptor argument for fsetattrlist() is not a valid file descriptor.
[]
The volume is read-only.
[]
Search permission is denied for a component of the path prefix for setattrlist().
[]
Too many symbolic links were encountered in translating the pathname for setattrlist().
[]
FSOPT_NOFOLLOW_ANY was passed and a symbolic link was encountered in translating the pathname for setattrlist().
[]
path, attrList or points to an invalid address.
[]
The bitmapcount field of attrList is not ATTR_BIT_MAP_COUNT.
[]
You try to set an invalid attribute.
[]
You try to set an attribute that is read-only.
[]
You try to set volume attributes and directory or file attributes at the same time.
[]
You try to set volume attributes but path does not reference the root of the volume.
[]
You try to set an attribute that can only be set by the owner.
[]
You try to set an attribute that's only settable if you have write permission, and you do not have write permission.
[]
The buffer size you specified in attrBufSize is too small to hold all the attributes that you are trying to set.
[]
An I/O error occurred while reading from or writing to the file system.

In addition to the errors returned by the setattrlist(), the setattrlistat() function may fail if:

[]
The path argument does not specify an absolute path and the fd argument is neither AT_FDCWD nor a valid file descriptor open for searching.
[]
The path argument is not an absolute path and fd is neither AT_FDCWD nor a file descriptor associated with a directory.

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.

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 {
    u_int32_t       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;
}

chflags(2), chmod(2), chown(2), getattrlist(2), getdirentriesattr(2), searchfs(2), utimes(2)

A setattrlist() function call appeared in Darwin 1.3.1 (Mac OS X version 10.0). The setatrlistat function call first appeared in macOS version 10.13.

December 15, 2003 Darwin