--- name: "getattrlist" section: "2" platform: "macos" package: "xnu" version: "12377.121.6" release: "macOS 26.5" platforms: ["macos"] url: "https://new.carta.tech/getattrlist" --- # getattrlist(2) get file system attributes ## NAME **getattrlist**, **fgetattrlist**, **getattrlistat** – get file system attributes ## SYNOPSIS **#include \** **#include \** *int*\ **getattrlist**(*const char\* path*, *struct attrlist \* attrList*, *void \* attrBuf*, *size\_t attrBufSize*, *unsigned long options*); *int*\ **fgetattrlist**(*int fd*, *struct attrlist \* attrList*, *void \* attrBuf*, *size\_t attrBufSize*, *unsigned long options*); *int*\ **getattrlistat**(*int fd*, *const char \*path*, *struct attrlist \* attrList*, *void \* attrBuf*, *size\_t attrBufSize*, *unsigned long options*); ## DESCRIPTION The **getattrlist**() function returns attributes (that is, metadata) of file system objects. **getattrlist**() works on the file system object named by *path*, while **fgetattrlist**() works on the provided file descriptor *fd*. The **getattrlistat**() system call is equivalent to **getattrlist**() except in the case where *path* specifies a relative path. In this case the attributes are returned 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 **getattrlistat**() 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 **getattrlist**(). You can think of **getattrlist**() as a seriously enhanced version of [stat(2)](/stat/2.md). The functions return attributes about the specified file system object into the buffer specified by *attrBuf* and *attrBufSize*. The *attrList* parameter determines what attributes are returned. The *options* parameter lets you control specific aspects of the function's behavior. Not all volumes support all attributes. See the discussion of ATTR\_VOL\_ATTRIBUTES for a discussion of how to determine whether a particular volume supports a particular attribute. Furthermore, you should only request the attributes that you need. Some attributes are expensive to calculate on some volume formats. For example, ATTR\_DIR\_ENTRYCOUNT is usually expensive to calculate on non-HFS \[Plus\] volumes. If you don't need a particular attribute, you should not ask for it. The *path* parameter must reference a valid file system object. Read, write or execute permission of the object itself is not required, but all directories listed in the path name leading to the object must be searchable. The *attrList* parameter is a pointer to an *attrlist* structure, as defined by ⟨*sys/attr.h*⟩ (shown below). It determines what attributes are returned by the function. You are responsible for filling out all fields of this structure before calling the function. ``` typedef u_int32_t attrgroup_t; struct attrlist { u_short bitmapcount; /* number of attr. bit sets in list */ u_int16_t reserved; /* (to maintain 4-byte alignment) */ attrgroup_t commonattr; /* common attribute group */ attrgroup_t volattr; /* volume attribute group */ attrgroup_t dirattr; /* directory attribute group */ attrgroup_t fileattr; /* file attribute group */ attrgroup_t forkattr; /* fork attribute group */ }; #define ATTR_BIT_MAP_COUNT 5 ``` The fields of the *attrlist* structure are defined as follows. - bitmapcount Number of attribute bit sets in the structure. In current systems you must set this to ATTR\_BIT\_MAP\_COUNT. - reserved Reserved. You must set this to 0. - commonattr A bit set that specifies the common attributes that you require. Common attributes relate to all types of file system objects. See below for a description of these attributes. - volattr A bit set that specifies the volume attributes that you require. Volume attributes relate to volumes (that is, mounted file systems). See below for a description of these attributes. You must set ATTR\_VOL\_INFO in the volattr field if you request any other volume attributes. In addition, you can't request volume attributes if you also request file, directory, fork or extended common attributes. In addition, you can't request volume attributes if you also request the common attributes ATTR\_CMN\_EXTENDED\_SECURITY, ATTR\_CMN\_UUID, ATTR\_CMN\_GRPUUID, ATTR\_CMN\_FILEID, or ATTR\_CMN\_PARENTID. - dirattr A bit set that specifies the directory attributes that you require. See below for a description of these attributes. - fileattr A bit set that specifies the file attributes that you require. See below for a description of these attributes. - forkattr A bit set that specifies the fork attributes that you require. Fork attributes relate to the actual data in the file, which can be held in multiple named contiguous ranges, or forks. See below for a description of these attributes. If the FSOPT\_ATTR\_CMN\_EXTENDED option is given, this bit set is reinterpreted as extended common attributes attributes, also described below. Unless otherwise noted in the lists below, attributes are read-only. Attributes labelled as read/write can be set using [setattrlist(2)](/setattrlist/2.md). The *attrBuf* and *attrBufSize* parameters specify a buffer into which the function places attribute values. The format of this buffer is sufficiently complex that its description requires a separate section (see below). The initial contents of this buffer are ignored. The *options* parameter is a bit set that controls the behaviour of the functions. The following option bits are defined. - FSOPT\_NOFOLLOW If this bit is set, **getattrlist**() will not follow a symlink if it occurs as the last component of *path*. - FSOPT\_NOFOLLOW\_ANY If this bit is set, **getattrlist**() will not follow a symlink if it occurs as the last component of *path*. In addition an error is returned if a symlink is encountered before the last component of *path*. - FSOPT\_RESOLVE\_BENEATH If this bit is set, path resolution must not escape the directory associated with the file descriptor. - FSOPT\_UNIQUE If this bit is set, the path lookup will fail if the target file has multiple hard links. - FSOPT\_REPORT\_FULLSIZE The size of the attributes reported (in the first *u\_int32\_t* field in the attribute buffer) will be the size needed to hold all the requested attributes; if not set, only the attributes actually returned will be reported. This allows the caller to determine if any truncation occurred. - FSOPT\_PACK\_INVAL\_ATTRS If this is bit is set, then all requested attributes, even ones that are not supported by the object or file system, will be returned. Default values will be used for the invalid ones. Requires that ATTR\_CMN\_RETURNED\_ATTRS be requested. - FSOPT\_ATTR\_CMN\_EXTENDED If this is bit is set, then ATTR\_CMN\_GEN\_COUNT and ATTR\_CMN\_DOCUMENT\_ID can be requested. When this option is used, forkattrs are reinterpreted as a set of extended common attributes. - FSOPT\_RETURN\_REALDEV If this is bit is set, then ATTR\_CMN\_DEVID and ATTR\_CMN\_FSID will return the values corresponding to the physical volume they are on. When a filesystem supports VOL\_CAP\_INT\_VOLUME\_GROUPS, it is possible that the filesystem may return a common logical value for these attributes otherwise. ## ATTRIBUTE BUFFER The data returned in the buffer described by *attrBuf* and *attrBufSize* is formatted as follows. 1. The first element of the buffer is a *u\_int32\_t* that contains the overall length, in bytes, of the attributes returned. This size includes the length field itself. 2. Following the length field is a list of attributes. Each attribute is represented by a field of its type, where the type is given as part of the attribute description (below). 3. The attributes are placed into the attribute buffer in the order that they are described below. 4. Each attribute is aligned to a 4-byte boundary (including 64-bit data types). If the attribute is of variable length, it is represented in the list by an *attrreference* structure, as defined by ⟨*sys/attr.h*⟩ (shown below). ``` typedef struct attrreference { int32_t attr_dataoffset; u_int32_t attr_length; } attrreference_t; ``` This structure contains a 'pointer' to the variable length attribute data. The *attr\_length* field is the length of the attribute data (in bytes). The *attr\_dataoffset* field is the offset in bytes from the *attrreference* structure to the attribute data. This offset will always be a multiple of sizeof(u\_int32\_t) bytes, so you can safely access common data types without fear of alignment exceptions. The **getattrlist**() function will silently truncate attribute data if *attrBufSize* is too small. The length field at the front of the attribute list always represents the length of the data actually copied into the attribute buffer. If the data is truncated, there is no easy way to determine the buffer size that's required to get all of the requested attributes. You should always pass an *attrBufSize* that is large enough to accommodate the known size of the attributes in the attribute list (including the leading length field). Because the returned attributes are simply truncated if the buffer is too small, it's possible for a variable length attribute to reference data beyond the end of the attribute buffer. That is, it's possible for the attribute data to start beyond the end of the attribute buffer (that is, if *attrRef* is a pointer to the *attrreference\_t*, ( ( (char \*) *attrRef* ) + *attr\_dataoffset* ) \> ( ( (char \*) *attrBuf* ) + *attrSize* ) ) or, indeed, for the attribute data to extend beyond the end of the attribute buffer (that is, ( ( (char \*) *attrRef* ) + *attr\_dataoffset* + *attr\_length* ) \> ( ( (char \*) *attrBuf* ) + *attrSize* ) ). If this happens you must increase the size of the buffer and call **getattrlist**() to get an accurate copy of the attribute. ## COMMON ATTRIBUTES Common attributes relate to all types of file system objects. The following common attributes are defined. - ATTR\_CMN\_RETURNED\_ATTRS An *attribute\_set\_t* structure which is used to report which of the requested attributes were actually returned. This attribute, when requested, will always be the first attribute returned. By default, unsupported attributes will be skipped (i.e. not packed into the output buffer). This behavior can be over-ridden using the FSOPT\_PACK\_INVAL\_ATTRS option flag. Both [getattrlist(2)](/getattrlist/2.md) and [getattrlistbulk(2)](/getattrlistbulk/2.md) support this attribute while [searchfs(2)](/searchfs/2.md) does not. - ATTR\_CMN\_NAME An *attrreference* structure containing the name of the file system object as UTF-8 encoded, null terminated C string. The attribute data length will not be greater than NAME\_MAX + 1 characters, which is NAME\_MAX \* 3 + 1 bytes (as one UTF-8-encoded character may take up to three bytes). - ATTR\_CMN\_DEVID A *dev\_t* containing the device number of the device on which this file system object's volume is mounted. Equivalent to the *st\_dev* field of the *stat* structure returned by [stat(2)](/stat/2.md). - ATTR\_CMN\_FSID An *fsid\_t* structure containing the file system identifier for the volume on which the file system object resides. Equivalent to the *f\_fsid* field of the *statfs* structure returned by [statfs(2)](/statfs/2.md). - ATTR\_CMN\_OBJTYPE An *fsobj\_type\_t* that identifies the type of file system object. The values are taken from *enum* *vtype* in ⟨*sys/vnode.h*⟩. - ATTR\_CMN\_OBJTAG An *fsobj\_tag\_t* that identifies the type of file system containing the object. The values are taken from *enum* *vtagtype* in ⟨*sys/vnode.h*⟩. - ATTR\_CMN\_OBJID An *fsobj\_id\_t* structure that uniquely identifies the file system object within a mounted volume for the duration of its mount; this identifier is not guaranteed to be persistent for the volume and may change every time the volume is mounted. On HFS+ volumes, the ATTR\_CMN\_OBJID of a file system object is distinct from the ATTR\_CMN\_OBJID of any hard link to that file system object. Although the ATTR\_CMN\_OBJID of a file system object may appear similar (in whole or in part) to it's ATTR\_CMN\_FILEID (see description of ATTR\_CMN\_FILEID below), **no relation between the two attributes should ever be implied.** ATTR\_CMN\_OBJID is deprecated starting with macOS 10.13, iOS 11.0, watchOS 4.0 and tvOS 11.0 and ATTR\_CMNEXT\_LINKID should be used in its place. ATTR\_CMN\_OBJID can only be used on older operating systems only if the file system doesn't 64 bit IDs. See the **getLinkIDInfo**() function in the EXAMPLES section. - ATTR\_CMN\_OBJPERMANENTID An *fsobj\_id\_t* structure that uniquely and persistently identifies the file system object within its volume; persistence implies that this attribute is unaffected by mount/unmount operations on the volume. Some file systems can not return this attribute when the volume is mounted read-only and will fail the request with error EROFS.\ (e.g. original HFS modifies on disk structures to generate persistent identifiers, and hence cannot do so if the volume is mounted read only.) - ATTR\_CMN\_PAROBJID An *fsobj\_id\_t* structure that uniquely identifies the parent directory of the file system object within a mounted volume, for the duration of the volume mount; this identifier is not guaranteed to be persistent for the volume and may change every time the volume is mounted. If a file system object is hard linked from multiple directories, the parent directory returned for this attribute is non deterministic; it can be any one of the parent directories of this object. For some volume formats the computing cost for this attribute is significant; developers are advised to request this attribute sparingly. - ATTR\_CMN\_SCRIPT (read/write) A *text\_encoding\_t* containing a text encoding hint for the file system object's name. It is included to facilitate the lossless round trip conversion of names between Unicode and traditional Mac OS script encodings. File systems that do not have an appropriate text encoding value should return kTextEncodingMacUnicode. - ATTR\_CMN\_CRTIME (read/write) A *timespec* structure containing the time that the file system object was created. - ATTR\_CMN\_MODTIME (read/write) A *timespec* structure containing the time that the file system object was last modified. Equivalent to the *st\_mtimespec* field of the *stat* structure returned by [stat(2)](/stat/2.md). - ATTR\_CMN\_CHGTIME A *timespec* structure containing the time that the file system object's attributes were last modified. Equivalent to the *st\_ctimespec* field of the *stat* structure returned by [stat(2)](/stat/2.md). - ATTR\_CMN\_ACCTIME (read/write) A *timespec* structure containing the time that the file system object was last accessed. Equivalent to the *st\_atimespec* field of the *stat* structure returned by [stat(2)](/stat/2.md). - ATTR\_CMN\_BKUPTIME (read/write) A *timespec* structure containing the time that the file system object was last backed up. This value is for use by backup utilities. The file system stores but does not interpret the value. - ATTR\_CMN\_FNDRINFO (read/write) 32 bytes of data for use by the Finder. Equivalent to the concatenation of a *FileInfo* structure and an *ExtendedFileInfo* structure (or, for directories, a *FolderInfo* structure and an *ExtendedFolderInfo* structure). This attribute is not byte swapped by the file system. The value of multibyte fields on disk is always big endian. When running on a little endian system (such as Darwin on x86), you must byte swap any multibyte fields. - ATTR\_CMN\_OWNERID (read/write) A *uid\_t* containing the owner of the file system object. Equivalent to the *st\_uid* field of the *stat* structure returned by [stat(2)](/stat/2.md). - ATTR\_CMN\_GRPID (read/write) A *gid\_t* containing the group of the file system object. Equivalent to the *st\_gid* field of the *stat* structure returned by [stat(2)](/stat/2.md). - ATTR\_CMN\_ACCESSMASK (read/write) A *u\_int32\_t* containing the access permissions of the file system object. Equivalent to the *st\_mode* field of the *stat* structure returned by [stat(2)](/stat/2.md). Only the permission bits of *st\_mode* are valid; other bits should be ignored, e.g., by masking with ~S\_IFMT. - ATTR\_CMN\_FLAGS (read/write) A *u\_int32\_t* containing file flags. Equivalent to the *st\_flags* field of the *stat* structure returned by [stat(2)](/stat/2.md). For more information about these flags, see [chflags(2)](/chflags/2.md). - ATTR\_CMN\_GEN\_COUNT A *u\_int32\_t* containing a non zero monotonically increasing generation count for this file system object. The generation count tracks the number of times the data in a file system object has been modified. No meaning can be implied from its value. The value of the generation count for a file system object can be compared against a previous value of the same file system object for equality; i.e. an unchanged generation count indicates identical data. Requesting this attribute requires the FSOPT\_ATTR\_CMN\_EXTENDED option flag. A generation count value of 0 is invalid and cannot be used to determine data change. The generation count is invalid while a file is mmap'ed. An invalid generation count value of 0 will be returned for mmap'ed files. - ATTR\_CMN\_DOCUMENT\_ID A *u\_int32\_t* containing the document id. The document id is a value assigned by the kernel to a document (which can be a file or directory) and is used to track the data regardless of where it gets moved. The document id survives safe saves; i.e it is sticky to the path it was assigned to. Requesting this attribute requires the FSOPT\_ATTR\_CMN\_EXTENDED option flag. A document id of 0 is invalid. - ATTR\_CMN\_USERACCESS A *u\_int32\_t* containing the effective permissions of the current user (the calling process's effective UID) for this file system object. You can test for read, write, and execute permission using R\_OK, W\_OK, and X\_OK, respectively. See [access(2)](/access/2.md) for more details. - ATTR\_CMN\_EXTENDED\_SECURITY A variable-length object (thus an *attrreference* structure) containing a *kauth\_filesec* structure, of which only the ACL entry is used. - ATTR\_CMN\_UUID A *guid\_t* of the owner of the file system object. Analogous to ATTR\_CMN\_OWNERID. - ATTR\_CMN\_GRPUUID A *guid\_t* of the group to which the file system object belongs. Analoguous to ATTR\_CMN\_GRPID. - ATTR\_CMN\_FILEID A *u\_int64\_t* that uniquely identifies the file system object within its mounted volume. Equivalent to *st\_ino* field of the *stat* structure returned by [stat(2)](/stat/2.md). - ATTR\_CMN\_PARENTID A *u\_int64\_t* that identifies the parent directory of the file system object. - ATTR\_CMN\_FULLPATH An *attrreference* structure containing the full path (resolving all symlinks) to the file system object as a UTF-8 encoded, null terminated C string. The attribute data length will not be greater than PATH\_MAX. Inconsistent behavior may be observed when this attribute is requested on hard-linked items, particularly when the file system does not support ATTR\_CMN\_PARENTID natively. Callers should be aware of this when requesting the full path of a hard-linked item. - ATTR\_CMN\_ADDEDTIME A *timespec* that contains the time that the file system object was created or renamed into its containing directory. Note that inconsistent behavior may be observed when this attribute is requested on hard-linked items. - ATTR\_CMN\_DATA\_PROTECT\_FLAGS A *u\_int32\_t* that contains the file or directory's data protection class. ## VOLUME ATTRIBUTES Volume attributes relate to volumes (that is, mounted file systems). The following volume attributes are defined. - ATTR\_VOL\_INFO For historical reasons you must set ATTR\_VOL\_INFO in the *volattr* field if you request any other volume attributes. - ATTR\_VOL\_FSTYPE A *u\_int32\_t* containing the file system type. Equivalent to the *f\_type* field of the *statfs* structure returned by [statfs(2)](/statfs/2.md). Generally not a useful value. - ATTR\_VOL\_SIGNATURE A *u\_int32\_t* containing the volume signature word. This value is unique within a given file system type and lets you distinguish between different volume formats handled by the same file system. - ATTR\_VOL\_SIZE An *off\_t* containing the total size of the volume in bytes. - ATTR\_VOL\_SPACEFREE An *off\_t* containing the free space on the volume in bytes. - ATTR\_VOL\_SPACEAVAIL An *off\_t* containing the space, in bytes, on the volume available to non-privileged processes. This is the free space minus the amount of space reserved by the system to prevent critical disk exhaustion errors. Non-privileged programs, like a disk management tool, should use this value to display the space available to the user. ATTR\_VOL\_SPACEAVAIL is to ATTR\_VOL\_SPACEFREE as *f\_bavail* is to *f\_bfree* in [statfs(2)](/statfs/2.md). - ATTR\_VOL\_SPACEUSED An *off\_t* containing the total space used on the volume in bytes. On space sharing volumes, this value may not be identical to the difference between the volume's size and its free space. - ATTR\_VOL\_MINALLOCATION An *off\_t* containing the minimum allocation size on the volume in bytes. If you create a file containing one byte, it will consume this much space. - ATTR\_VOL\_ALLOCATIONCLUMP An *off\_t* containing the allocation clump size on the volume, in bytes. As a file is extended, the file system will attempt to allocate this much space each time in order to reduce fragmentation. - ATTR\_VOL\_IOBLOCKSIZE A *u\_int32\_t* containing the optimal block size when reading or writing data. Equivalent to the *f\_iosize* field of the *statfs* structure returned by [statfs(2)](/statfs/2.md). - ATTR\_VOL\_OBJCOUNT A *u\_int32\_t* containing the number of file system objects on the volume. - ATTR\_VOL\_FILECOUNT A *u\_int32\_t* containing the number of files on the volume. - ATTR\_VOL\_DIRCOUNT A *u\_int32\_t* containing the number of directories on the volume. - ATTR\_VOL\_MAXOBJCOUNT A *u\_int32\_t* containing the maximum number of file system objects that can be stored on the volume. - ATTR\_VOL\_MOUNTPOINT An *attrreference* structure containing the path to the volume's mount point as a UTF-8 encoded, null terminated C string. The attribute data length will not be greater than MAXPATHLEN. Equivalent to the *f\_mntonname* field of the *statfs* structure returned by [statfs(2)](/statfs/2.md). - ATTR\_VOL\_NAME (read/write) An *attrreference* structure containing the name of the volume as a UTF-8 encoded, null terminated C string. The attribute data length will not be greater than NAME\_MAX + 1. This attribute is only read/write if the VOL\_CAP\_INT\_VOL\_RENAME bit is set in the volume capabilities (see below). - ATTR\_VOL\_MOUNTFLAGS A *u\_int32\_t* containing the volume mount flags. This is a copy of the value passed to the *flags* parameter of [mount(2)](/mount/2.md) when the volume was mounted. Equivalent to the *f\_flags* field of the *statfs* structure returned by [statfs(2)](/statfs/2.md). - ATTR\_VOL\_MOUNTEDDEVICE An *attrreference* structure that returns the same value as the *f\_mntfromname* field of the *statfs* structure returned by [statfs(2)](/statfs/2.md). For local volumes this is the path to the device on which the volume is mounted as a UTF-8 encoded, null terminated C string. For network volumes, this is a unique string that identifies the mount. The attribute data length will not be greater than MAXPATHLEN. - ATTR\_VOL\_ENCODINGSUSED An *unsigned* *long* *long* containing a bitmap of the text encodings used on this volume. For more information about this, see the discussion of *encodingsBitmap* in DTS Technote 1150 "HFS Plus Volume Format". - ATTR\_VOL\_CAPABILITIES A *vol\_capabilities\_attr\_t* structure describing the optional features supported by this volume. See below for a discussion of volume capabilities. - ATTR\_VOL\_UUID A *uuid\_t* containing the file system UUID. Typically this will be a version 5 UUID. - ATTR\_VOL\_MOUNTEXTFLAGS A *u\_int32\_t* containing the volume extended mount flags. Equivalent to the *f\_flags\_ext* field of the *statfs* structure returned by [statfs(2)](/statfs/2.md). - ATTR\_VOL\_QUOTA\_SIZE An *off\_t* containing the maximum size of the volume in bytes. - ATTR\_VOL\_RESERVED\_SIZE An *off\_t* containing the minimum size of the volume in bytes. - ATTR\_VOL\_ATTRIBUTES A *vol\_attributes\_attr\_t* structure describing the attributes supported by this volume. This structure is discussed below, along with volume capabilities. - ATTR\_VOL\_FSTYPENAME An *attrreference* structure containing the file system type name as a UTF-8 encoded, null terminated C string. The attribute data length will not be greater than MFSTYPENAMELEN. - ATTR\_VOL\_FSSUBTYPE A *u\_int32\_t* containing the file system sub-type. Equivalent to the *f\_fssubtype* field of the *statfs* structure returned by [statfs(2)](/statfs/2.md). - ATTR\_VOL\_OWNER A *uid\_t* containing the user that mounted the filesystem. Equivalent to the *f\_owner* field of the *statfs* structure returned by [statfs(2)](/statfs/2.md). ## DIRECTORY ATTRIBUTES The following directory attributes are defined. - ATTR\_DIR\_LINKCOUNT A *u\_int32\_t* containing the number of hard links to the directory; this does not include the historical "." and ".." entries. For file systems that do not support hard links to directories, this value will be 1. - ATTR\_DIR\_ENTRYCOUNT A *u\_int32\_t* containing the number of file system objects in the directory, not including any synthetic items. The historical "." and ".." entries are also excluded from this count. - ATTR\_DIR\_MOUNTSTATUS A *u\_int32\_t* containing flags describing what's mounted on the directory. Currently the only flag defined is DIR\_MNTSTATUS\_MNTPOINT, which indicates that there is a file system mounted on this directory. - ATTR\_DIR\_ALLOCSIZE An *off\_t* containing the number of bytes on disk used by the directory (the physical size). - ATTR\_DIR\_IOBLOCKSIZE A *u\_int32\_t* containing the optimal block size when reading or writing data. - ATTR\_DIR\_DATALENGTH An *off\_t* containing the length of the directory in bytes (the logical size). Requested directory attributes are not returned for file system objects that are not directories. ## FILE ATTRIBUTES The following file attributes are defined. - ATTR\_FILE\_LINKCOUNT A *u\_int32\_t* containing the number of hard links to this file. Equivalent to the *st\_nlink* field of the *stat* structure returned by [stat(2)](/stat/2.md). - ATTR\_FILE\_TOTALSIZE An *off\_t* containing the total number of bytes in all forks of the file (the logical size). - ATTR\_FILE\_ALLOCSIZE An *off\_t* containing a count of the bytes on disk used by all of the file's forks (the physical size). - ATTR\_FILE\_IOBLOCKSIZE A *u\_int32\_t* containing the optimal block size when reading or writing this file's data. - ATTR\_FILE\_CLUMPSIZE A *u\_int32\_t* containing the allocation clump size for this file, in bytes. As the file is extended, the file system will attempt to allocate this much space each time in order to reduce fragmentation. This value applies to the data fork. - ATTR\_FILE\_DEVTYPE (read/write) A *u\_int32\_t* containing the device type for a special device file. Equivalent to the *st\_rdev* field of the *stat* structure returned by [stat(2)](/stat/2.md). - ATTR\_FILE\_FILETYPE A *u\_int32\_t* that whose value is reserved. Clients should ignore its value. New volume format implementations should not support this attribute. - ATTR\_FILE\_FORKCOUNT A *u\_int32\_t* containing the number of forks in the file. No built-in file systems on Mac OS X currently support forks other than the data and resource fork. - ATTR\_FILE\_FORKLIST An *attrreference* structure containing a list of named forks of the file. No built-in file systems on Mac OS X currently support forks other than the data and resource fork. Because of this, the structure of this attribute's value is not yet defined. - ATTR\_FILE\_DATALENGTH An *off\_t* containing the length of the data fork in bytes (the logical size). - ATTR\_FILE\_DATAALLOCSIZE An *off\_t* containing a count of the bytes on disk used by the data fork (the physical size). - ATTR\_FILE\_DATAEXTENTS An *extentrecord* array for the data fork. The array contains eight *diskextent* structures which represent the first eight extents of the fork. This attributes exists for compatibility reasons. New clients should not use this attribute. Rather, they should use the F\_LOG2PHYS command in [fcntl(2)](/fcntl/2.md). In current implementations the value may not be entirely accurate for a variety of reasons. - ATTR\_FILE\_RSRCLENGTH An *off\_t* containing the length of the resource fork in bytes (the logical size). - ATTR\_FILE\_RSRCALLOCSIZE An *off\_t* containing a count of the bytes on disk used by the resource fork (the physical size). - ATTR\_FILE\_RSRCEXTENTS An *extentrecord* array for the resource fork. The array contains eight *diskextent* structures which represent the first eight extents of the fork. See also ATTR\_FILE\_DATAEXTENTS. File attributes are used for any file system object that is not a directory, not just ordinary files. Requested file attributes are not returned for file system objects that are directories. ## FORK ATTRIBUTES Fork attributes relate to the actual data in the file, which can be held in multiple named contiguous ranges, or forks. These cannot be used if the FSOPT\_ATTR\_CMN\_EXTENDED is given. The following fork attributes are defined. - ATTR\_FORK\_TOTALSIZE Deprecated. An *off\_t* containing the length of the fork in bytes (the logical size). - ATTR\_FORK\_ALLOCSIZE Deprecated. An *off\_t* containing a count of the bytes on disk used by the fork (the physical size). - ATTR\_FORK\_RESERVED Reserved. You must set this to 0. Fork attributes are deprecated and all bits are reserved. They are not properly implemented by any current Mac OS X volume format implementation. We strongly recommend that client programs do not request fork attributes. If you are implementing a volume format, you should not support these attributes. ## COMMON EXTENDED ATTRIBUTES Common extended attributes are like common attributes except that they are set in the forkattr field and can only be used if the FSOPT\_ATTR\_CMN\_EXTENDED option is given. Use of these attributes is mutually exclusive with the above fork attributes. - ATTR\_CMNEXT\_RELPATH An *attrreference* structure containing the mount-relative path of the file system object as a UTF-8 encoded, null terminated C string. The attribute data length will not be greater than PATH\_MAX. Inconsistent behavior may be observed when this attribute is requested on hard-linked items, particularly when the file system does not support ATTR\_CMN\_PARENTID natively. Callers should be aware of this when requesting the relative path of a hard-linked item. - ATTR\_CMNEXT\_PRIVATESIZE An *off\_t* containing the number of bytes that are **not** trapped inside a clone or snapshot, and which would be freed immediately if the file were deleted. - ATTR\_CMNEXT\_LINKID A *u\_int64\_t* that uniquely identifies the file system object within a mounted volume for the duration of its mount. This identifier is persistent on volumes that support the VOL\_CAP\_FMT\_PERSISTENTOBJECTIDS capability, such as HFS+ and APFS. On HFS+ and APFS volumes, the ATTR\_CMNEXT\_LINKID of a file system object is distinct from the ATTR\_CMNEXT\_LINKID of any hard link to that file system object. Although the ATTR\_CMNEXT\_LINKID of a file system object may appear similar (in whole or in part) to its ATTR\_CMN\_FILEID (see description of ATTR\_CMN\_FILEID above), **no relation between the two attributes should ever be implied.** - ATTR\_CMNEXT\_NOFIRMLINKPATH An *attrreference* structure containing a path that does not have firmlinks of the file system object as a UTF-8 encoded, null terminated C string. The attribute data length will not be greater than PATH\_MAX. Inconsistent behavior may be observed when this attribute is requested on hard-linked items, particularly when the file system does not support ATTR\_CMN\_PARENTID natively. Callers should be aware of this when requesting the canonical path of a hard-linked item. - ATTR\_CMNEXT\_REALDEVID A *dev\_t* containing the real device number of the device on which this file system object's volume is mounted. Equivalent to the *st\_dev* field of the *stat* structure returned by [stat(2)](/stat/2.md). - ATTR\_CMNEXT\_REALFSID An *fsid\_t* structure containing the real file system identifier for the volume on which the file system object resides. Equivalent to the *f\_fsid* field of the *statfs* structure returned by [statfs(2)](/statfs/2.md). - ATTR\_CMNEXT\_CLONEID A *u\_int64\_t* that uniquely identifies the data stream associated with the file system object. Useful for finding which files are pure clones of each other (as they will have the same clone-id). - ATTR\_CMNEXT\_EXT\_FLAGS A *u\_int64\_t* that contains additional flags with information about the file. The flags are: - EF\_MAY\_SHARE\_BLOCKS If this bit is set then the file may share blocks with another file (i.e. it may be a clone of another file). - EF\_NO\_XATTRS If this bit is set then the file has no extended attributes. Useful for avoiding a call to listxattr(). - EF\_IS\_SYNC\_ROOT If this bit is set the directory is a "sync root". This bit will never be set for regular files. - EF\_IS\_PURGEABLE If this bit is set the item is a "purgeable" item that can be deleted by the file system when asked to free space. - EF\_IS\_SPARSE If this bit is set the item has sparse regions. - EF\_IS\_SYNTHETIC If this bit is set the item is a synthetic directory/symlink. - EF\_SHARES\_ALL\_BLOCKS If this bit is set then the file shares all of its blocks with another file (i.e. it is a full clone of another file). For compatibility reasons, EF\_SHARES\_ALL\_BLOCKS means EF\_MAY\_SHARE\_BLOCKS as well. - ATTR\_CMNEXT\_RECURSIVE\_GENCOUNT A *u\_int64\_t* that represents the recursive generation count of a directory that has been marked as maintain-dir-stats in an apfs file system. This gencount is updated any time any child is modified (as part of the contract that a maintain-dir-stats directory manages). If the directory is not marked maintain-dir-stats, a zero is returned. - ATTR\_CMNEXT\_ATTRIBUTION\_TAG An optional *u\_int64\_t* id that represents the bundle id (owner) associated with the file (zero means the file isn't attributed yet) - ATTR\_CMNEXT\_CLONE\_REFCNT A *u\_int32\_t* that represents the number of full clones (each shares all of its blocks with this file). ## VOLUME CAPABILITIES Not all volumes support all features. The ATTR\_VOL\_CAPABILITIES attribute returns a *vol\_capabilities\_attr\_t* structure (shown below) that indicates which features are supported by the volume. ``` typedef u_int32_t vol_capabilities_set_t[4]; #define VOL_CAPABILITIES_FORMAT 0 #define VOL_CAPABILITIES_INTERFACES 1 #define VOL_CAPABILITIES_RESERVED1 2 #define VOL_CAPABILITIES_RESERVED2 3 typedef struct vol_capabilities_attr { vol_capabilities_set_t capabilities; vol_capabilities_set_t valid; } vol_capabilities_attr_t; ``` The structure contains two fields, *capabilities* and *valid*. Each consists of an array of four elements. The arrays are indexed by the following values. - VOL\_CAPABILITIES\_FORMAT This element contains information about the volume format. See VOL\_CAP\_FMT\_PERSISTENTOBJECTIDS and so on, below. - VOL\_CAPABILITIES\_INTERFACES This element contains information about which optional functions are supported by the volume format implementation. See VOL\_CAP\_INT\_SEARCHFS and so on, below. - VOL\_CAPABILITIES\_RESERVED1 Reserved. A file system implementation should set this element to zero. A client program should ignore this element. - VOL\_CAPABILITIES\_RESERVED2 Reserved. A file system implementation should set this element to zero. A client program should ignore this element. The *valid* field contains bit sets that indicate which flags are known to the volume format implementation. Each bit indicates whether the contents of the corresponding bit in the *capabilities* field is valid. The *capabilities* field contains bit sets that indicate whether a particular feature is implemented by this volume format. The following bits are defined in the first element (indexed by VOL\_CAPABILITIES\_FORMAT) of the *capabilities* and *valid* fields of the *vol\_capabilities\_attr\_t* structure. - VOL\_CAP\_FMT\_PERSISTENTOBJECTIDS If this bit is set the volume format supports persistent object identifiers and can look up file system objects by their IDs. See ATTR\_CMN\_OBJPERMANENTID for details about how to obtain these identifiers. - VOL\_CAP\_FMT\_SYMBOLICLINKS If this bit is set the volume format supports symbolic links. - VOL\_CAP\_FMT\_HARDLINKS If this bit is set the volume format supports hard links. - VOL\_CAP\_FMT\_JOURNAL If this bit is set the volume format supports a journal used to speed recovery in case of unplanned restart (such as a power outage or crash). This does not necessarily mean the volume is actively using a journal. Introduced with Darwin 7.0 (Mac OS X version 10.3). - VOL\_CAP\_FMT\_JOURNAL\_ACTIVE If this bit is set the volume is currently using a journal for speedy recovery after an unplanned restart. This bit can be set only if VOL\_CAP\_FMT\_JOURNAL is also set. Introduced with Darwin 7.0 (Mac OS X version 10.3). - VOL\_CAP\_FMT\_NO\_ROOT\_TIMES If this bit is set the volume format does not store reliable times for the root directory, so you should not depend on them to detect changes, identify volumes across unmount/mount, and so on. Introduced with Darwin 7.0 (Mac OS X version 10.3). - VOL\_CAP\_FMT\_SPARSE\_FILES If this bit is set the volume format supports sparse files, that is, files which can have 'holes' that have never been written to, and thus do not consume space on disk. A sparse file may have an allocated size on disk that is less than its logical length (that is, ATTR\_FILE\_ALLOCSIZE \< ATTR\_FILE\_TOTALSIZE ). Introduced with Darwin 7.0 (Mac OS X version 10.3). - VOL\_CAP\_FMT\_ZERO\_RUNS For security reasons, parts of a file (runs) that have never been written to must appear to contain zeroes. When this bit is set, the volume keeps track of allocated but unwritten runs of a file so that it can substitute zeroes without actually writing zeroes to the media. This provides performance similar to sparse files, but not the space savings. Introduced with Darwin 7.0 (Mac OS X version 10.3). - VOL\_CAP\_FMT\_CASE\_SENSITIVE If this bit is set the volume format treats upper and lower case characters in file and directory names as different. Otherwise an upper case character is equivalent to a lower case character, and you can't have two names that differ solely in the case of the characters. Introduced with Darwin 7.0 (Mac OS X version 10.3). - VOL\_CAP\_FMT\_CASE\_PRESERVING If this bit is set the volume format preserves the case of file and directory names. Otherwise the volume may change the case of some characters (typically making them all upper or all lower case). A volume that sets VOL\_CAP\_FMT\_CASE\_SENSITIVE must also set VOL\_CAP\_FMT\_CASE\_PRESERVING. Introduced with Darwin 7.0 (Mac OS X version 10.3). - VOL\_CAP\_FMT\_FAST\_STATFS This bit is used as a hint to upper layers to indicate that [statfs(2)](/statfs/2.md) is fast enough that its results need not be cached by the caller. A volume format implementation that caches the [statfs(2)](/statfs/2.md) information in memory should set this bit. An implementation that must always read from disk or always perform a network transaction to satisfy [statfs(2)](/statfs/2.md) should not set this bit. Introduced with Darwin 7.0 (Mac OS X version 10.3). - VOL\_CAP\_FMT\_2TB\_FILESIZE If this bit is set the volume format supports file sizes larger than 4GB, and potentially up to 2TB; it does not indicate whether the file system supports files larger than that. Introduced with Darwin 8.0 (Mac OS X version 10.4). - VOL\_CAP\_FMT\_OPENDENYMODES If this bit is set, the volume format supports open deny modes (e.g., "open for read write, deny write"). - VOL\_CAP\_FMT\_HIDDEN\_FILES If this bit is set, the volume format supports the UF\_HIDDEN file flag, and the UF\_HIDDEN flag is mapped to that volume's native "hidden" or "invisible" bit (e.g., the invisible bit from the Finder Info extended attribute). - VOL\_CAP\_FMT\_PATH\_FROM\_ID If this bit is set, the volume format supports the ability to derive a pathname to the root of the file system given only the ID of an object. This also implies that object IDs on this file system are persistent and not recycled. Most file systems will not support this capability. - VOL\_CAP\_FMT\_NO\_VOLUME\_SIZES If this bit is set the volume format does not support determining values for total data blocks, available blocks, or free blocks, as in *f\_blocks,* *f\_bavail,* and *f\_bfree* in the *struct*, *statfs* returned by [statfs(2)](/statfs/2.md). Historically, those values were set to 0xFFFFFFFF for volumes that did not support them. Introduced with Darwin 10.0 (Mac OS X version 10.6). - VOL\_CAP\_FMT\_64BIT\_OBJECT\_IDS If this bit is set, the volume format uses object IDs that are 64-bit. This means that ATTR\_CMN\_FILEID and ATTR\_CMN\_PARENTID are the primary means of obtaining object IDs from this volume. The values returned by ATTR\_CMN\_OBJID, ATTR\_CMN\_OBJPERMANENTID, and ATTR\_CMN\_PAROBJID can be interpreted as 64-bit object IDs instead of fsobj\_id\_t. - VOL\_CAP\_FMT\_DOCUMENT\_ID If this bit is set, the volume format supports document IDs (an ID which persists across object ID changes) for document revisions. - VOL\_CAP\_FMT\_NO\_IMMUTABLE\_FILES If this bit is set, the volume format does not support setting the UF\_IMMUTABLE flag. See ATTR\_CMN\_FLAGS for more details. - VOL\_CAP\_FMT\_NO\_PERMISSIONS If this bit is set, the volume format does not support setting file permissions. See ATTR\_CMN\_USERACCESS for more details. - VOL\_CAP\_FMT\_SHARED\_SPACE If this bit is set, the volume format supports having multiple logical filesystems in a single "partition" which share space. - VOL\_CAP\_FMT\_VOL\_GROUPS If this bit is set, the volume format supports having multiple logical filesystems which may be mounted and unmounted together and may present common filesystem identifier information. - VOL\_CAP\_FMT\_SEALED If this bit is set, the volume is cryptographically sealed and any modifications may render the volume unusable. - VOL\_CAP\_FMT\_CLONE\_MAPPING If this bit is set, the volume format supports full clone tracking. See ATTR\_CMNEXT\_CLONE\_REFCNT and ATTR\_CMNEXT\_CLONEID for more details. Other features like extended directory statistics, for fast directory sizing, and attribution tags may be supported as well. See VOL\_CAP\_INT\_ATTRIBUTION\_TAG for more details related to tagging. The following bits are defined in the second element (indexed by VOL\_CAPABILITIES\_INTERFACES) of the *capabilities* and *valid* fields of the *vol\_capabilities\_attr\_t* structure. - VOL\_CAP\_INT\_SEARCHFS If this bit is set the volume format implementation supports [searchfs(2)](/searchfs/2.md). - VOL\_CAP\_INT\_ATTRLIST If this bit is set the volume format implementation supports **getattrlist**() and [setattrlist(2)](/setattrlist/2.md). - VOL\_CAP\_INT\_NFSEXPORT If this bit is set the volume format implementation allows this volume to be exported via NFS. - VOL\_CAP\_INT\_READDIRATTR If this bit is set the volume format implementation supports getdirentriesattr(2). - VOL\_CAP\_INT\_EXCHANGEDATA If this bit is set the volume format implementation supports [exchangedata(2)](/exchangedata/2.md). Introduced with Darwin 7.0 (Mac OS X version 10.3). - VOL\_CAP\_INT\_COPYFILE If this bit is set the volume format implementation supports the (private and undocumented) copyfile() function. (This is not the [copyfile(3)](/copyfile/3.md) function.) Introduced with Darwin 7.0 (Mac OS X version 10.3). - VOL\_CAP\_INT\_ALLOCATE If this bit is set the volume format implementation supports the F\_PREALLOCATE selector of [fcntl(2)](/fcntl/2.md). Introduced with Darwin 7.0 (Mac OS X version 10.3). - VOL\_CAP\_INT\_VOL\_RENAME If this bit is set the volume format implementation allows you to modify the volume name using [setattrlist(2)](/setattrlist/2.md). Introduced with Darwin 7.0 (Mac OS X version 10.3). - VOL\_CAP\_INT\_ADVLOCK If this bit is set the volume format implementation supports advisory locking, that is, the F\_GETLK, F\_SETLK, and F\_SETLKW selectors to [fcntl(2)](/fcntl/2.md). Introduced with Darwin 7.0 (Mac OS X version 10.3). - VOL\_CAP\_INT\_FLOCK If this bit is set the volume format implementation supports whole file locks. This includes [flock(2)](/flock/2.md) and the O\_EXLOCK and O\_SHLOCK flags to [open(2)](/open/2.md). Introduced with Darwin 7.0 (Mac OS X version 10.3). - VOL\_CAP\_INT\_EXTENDED\_SECURITY If this bit is set the volume format implementation supports extended security controls (ACLs). Introduced with Darwin 8.0 (Mac OS X version 10.4). - VOL\_CAP\_INT\_USERACCESS If this bit is set the volume format implementation supports the ATTR\_CMN\_USERACCESS attribute. Introduced with Darwin 8.0 (Mac OS X version 10.4). - VOL\_CAP\_INT\_MANLOCK If this bit is set, the volume format implementation supports AFP-style mandatory byte range locks via [ioctl(2)](/ioctl/2.md). - VOL\_CAP\_INT\_EXTENDED\_ATTR If this bit is set, the volume format implementation supports native extended attributes (see [setxattr(2)](/setxattr/2.md)). - VOL\_CAP\_INT\_CLONE If this bit is set, the file system supports cloning files and directories. See [clonefileat(2)](/clonefileat/2.md) for more details. - VOL\_CAP\_INT\_SNAPSHOT If this bit is set, the file system supports snapshots. See [fs\_snapshot\_create(2)](/fs_snapshot_create/2.md) for more details. - VOL\_CAP\_INT\_NAMEDSTREAMS If this bit is set, the volume format implementation supports native named streams. - VOL\_CAP\_INT\_RENAME\_SWAP If this bit is set, the file system supports swapping file system objects. See [rename(2)](/rename/2.md) for more details. - VOL\_CAP\_INT\_RENAME\_EXCL If this bit is set, the file system supports an exclusive rename operation. See [rename(2)](/rename/2.md) for more details. - VOL\_CAP\_INT\_RENAME\_OPENFAIL If this bit is set, the file system may fail a rename operation of a directory if one of its descendents is open. See [rename(2)](/rename/2.md) for more details. - VOL\_CAP\_INT\_ATTRIBUTION\_TAG If this bit is set, the file system supports establishing an owner relationship between a file (excluding small files) and a process on the first read/write/truncate/clone operation. See ATTR\_CMNEXT\_ATTRIBUTION\_TAG for more details. - VOL\_CAP\_INT\_PUNCHHOLE If this bit is set, the file system supports the F\_PUNCHOLE operation. See [fcntl(2)](/fcntl/2.md) for more details. - VOL\_CAP\_INT\_BARRIERFSYNC If this bit is set, the file system supports the F\_BARRIERFSYNC operation. See [fcntl(2)](/fcntl/2.md) for more details. A volume can also report which attributes it supports. This information is returned by the ATTR\_VOL\_ATTRIBUTES attribute, which returns a *vol\_attributes\_attr\_t* structure (shown below). ``` typedef struct attribute_set { attrgroup_t commonattr; /* common attribute group */ attrgroup_t volattr; /* volume attribute group */ attrgroup_t dirattr; /* directory attribute group */ attrgroup_t fileattr; /* file attribute group */ attrgroup_t forkattr; /* fork attribute group */ } attribute_set_t; typedef struct vol_attributes_attr { attribute_set_t validattr; attribute_set_t nativeattr; } vol_attributes_attr_t; ``` The *validattr* field consists of a number of bit sets that indicate whether an attribute is supported by the volume format implementation. The *nativeattr* is similar except that the bit sets indicate whether an attribute is supported natively by the volume format. An attribute is supported natively if the volume format implementation does not have to do any complex conversions to access the attribute. For example, a volume format might support persistent object identifiers, but doing so requires a complex table lookup that is not part of the core volume format. In that case, the ATTR\_VOL\_ATTRIBUTES attribute would return ATTR\_CMN\_OBJPERMANENTID set in the *validattr* field of the *vol\_attributes\_attr\_t*, but not in the *nativeattr* field. ## 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 **getattrlist**(). The best way to test whether a volume supports this function is to simply call it and check the error result. **getattrlist**() will return ENOTSUP if it is not supported on a particular volume. The **getattrlist**() 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 **getattrlist**(), you should be careful to support the behaviour specified by this document. ## ERRORS **getattrlist**() and **fgetattrlist**() will fail if: - \[ENOTSUP\] The volume does not support the query. - \[ENOTDIR\] A component of the path prefix for **getattrlist**() is not a directory. - \[ENAMETOOLONG\] A component of a path name for **getattrlist**() exceeded NAME\_MAX characters, or an entire path name exceeded PATH\_MAX characters. - \[ENOENT\] The file system object for **getattrlist**() does not exist. - \[EBADF\] The file descriptor argument for **fgetattrlist**() is not a valid file descriptor. - \[EACCES\] Search permission is denied for a component of the path prefix for **getattrlist**(). - \[ELOOP\] Too many symbolic links were encountered in translating the pathname for **getattrlist**(). - \[ELOOP\] FSOPT\_NOFOLLOW\_ANY was passed and a symbolic link was encountered in translating the pathname for **getattrlist**(). - \[EFAULT\] *path*, *attrList* or *attrBuf* points to an invalid address. - \[ERANGE\] *attrBufSize* is too small to hold a u\_int32\_t. - \[EINVAL\] The *bitmapcount* field of *attrList* is not ATTR\_BIT\_MAP\_COUNT. - \[EINVAL\] You requested an invalid attribute. - \[EINVAL\] You requested an attribute that is not supported for this file system object. - \[EINVAL\] You requested volume attributes and directory or file attributes. - \[EINVAL\] You requested volume attributes but *path* does not reference the root of the volume. - \[EROFS\] The volume is read-only but must be modified in order to return this attribute. - \[EIO\] An I/O error occurred while reading from or writing to the file system. In addition to the errors returned by the **getattrlist**(), the **getattrlistat**() function may fail if: - \[EBADF\] 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. - \[ENOTDIR\] The *path* argument is not an absolute path and *fd* is neither AT\_FDCWD nor a file descriptor associated with a directory. - \[ENOTCAPABLE\] if FSOPT\_RESOLVE\_BENEATH was passed and *path* does not reside in the directory hierarchy beneath the starting directory. - \[ENOTCAPABLE\] if FSOPT\_UNIQUE was passed and *path* has multiple hard links. ## CAVEATS If you request any volume attributes, you must set ATTR\_VOL\_INFO in the *volattr* field, even though it generates no result in the attribute buffer. The order that attributes are stored in the attribute buffer almost invariably matches the order of attribute mask bit values. For example, ATTR\_CMN\_NAME (0x00000001) comes before ATTR\_CMN\_DEVID (0x00000002) because its value is smaller. When ordering attributes, you should always use the order in which they are described above. The *timespec* structure is 64-bits (two 32-bit elements) in 32-bit code, and 128-bits (two 64-bit elements) in 64-bit code; however, it is aligned on a 4-byte (32-bit) boundary, even in 64-bit code. If you use a structure for the attribute data, it must be correctly packed and aligned (see examples). Inconsistent behavior may be observed when the ATTR\_CMN\_FULLPATH attribute is requested on hard-linked items, particularly when the file system does not support ATTR\_CMN\_PARENTID natively. Callers should be aware of this when requesting the full path of a hard-linked item, especially if the full path crosses mount points. For more caveats, see also the compatibility notes above. ## EXAMPLES The following code prints the file type and creator of a file, assuming that the volume supports the required attributes. ``` #include #include #include #include #include #include #include typedef struct attrlist attrlist_t; struct FInfoAttrBuf { u_int32_t length; fsobj_type_t objType; char finderInfo[32]; } __attribute__((aligned(4), packed)); typedef struct FInfoAttrBuf FInfoAttrBuf; static int FInfoDemo(const char *path) { int err; attrlist_t attrList; FInfoAttrBuf attrBuf; 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) { assert(attrBuf.length == sizeof(attrBuf)); printf("Finder information for %s:\n", path); switch (attrBuf.objType) { case VREG: printf("file type = '%.4s'\n", &attrBuf.finderInfo[0]); printf("file creator = '%.4s'\n", &attrBuf.finderInfo[4]); break; case VDIR: printf("directory\n"); break; default: printf("other object type, %d\n", attrBuf.objType); break; } } return err; } ``` The following code is an alternative implementation that uses nested structures to group the related attributes. ``` #include #include #include #include #include #include #include #include typedef struct attrlist attrlist_t; struct FInfo2CommonAttrBuf { fsobj_type_t objType; char finderInfo[32]; } __attribute__((aligned(4), packed)); typedef struct FInfo2CommonAttrBuf FInfo2CommonAttrBuf; struct FInfo2AttrBuf { u_int32_t length; FInfo2CommonAttrBuf common; } __attribute__((aligned(4), packed));; typedef struct FInfo2AttrBuf FInfo2AttrBuf; static int FInfo2Demo(const char *path) { int err; attrlist_t attrList; FInfo2AttrBuf attrBuf; 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) { assert(attrBuf.length == sizeof(attrBuf)); printf("Finder information for %s:\n", path); switch (attrBuf.common.objType) { case VREG: printf( "file type = '%.4s'\n", &attrBuf.common.finderInfo[0] ); printf( "file creator = '%.4s'\n", &attrBuf.common.finderInfo[4] ); break; case VDIR: printf("directory\n"); break; default: printf( "other object type, %d\n", attrBuf.common.objType ); break; } } return err; } ``` The following example shows how to deal with variable length attributes. It assumes that the volume specified by *path* supports the necessary attributes. ``` #include #include #include #include #include #include #include #include typedef struct attrlist attrlist_t; struct VolAttrBuf { u_int32_t length; u_int32_t fileCount; u_int32_t dirCount; attrreference_t mountPointRef; attrreference_t volNameRef; char mountPointSpace[MAXPATHLEN]; char volNameSpace[MAXPATHLEN]; } __attribute__((aligned(4), packed)); typedef struct VolAttrBuf VolAttrBuf; static int VolDemo(const char *path) { int err; attrlist_t attrList; VolAttrBuf attrBuf; memset(&attrList, 0, sizeof(attrList)); attrList.bitmapcount = ATTR_BIT_MAP_COUNT; attrList.volattr = ATTR_VOL_INFO | ATTR_VOL_FILECOUNT | ATTR_VOL_DIRCOUNT | ATTR_VOL_MOUNTPOINT | ATTR_VOL_NAME; err = getattrlist(path, &attrList, &attrBuf, sizeof(attrBuf), 0); if (err != 0) { err = errno; } if (err == 0) { assert(attrBuf.length > offsetof(VolAttrBuf, mountPointSpace)); assert(attrBuf.length <= sizeof(attrBuf)); printf("Volume information for %s:\n", path); printf("ATTR_VOL_FILECOUNT: %u\n", attrBuf.fileCount); printf("ATTR_VOL_DIRCOUNT: %u\n", attrBuf.dirCount); printf( "ATTR_VOL_MOUNTPOINT: %.*s\n", (int) attrBuf.mountPointRef.attr_length, ( ((char *) &attrBuf.mountPointRef) + attrBuf.mountPointRef.attr_dataoffset ) ); printf( "ATTR_VOL_NAME: %.*s\n", (int) attrBuf.volNameRef.attr_length, ( ((char *) &attrBuf.volNameRef) + attrBuf.volNameRef.attr_dataoffset ) ); } return err; } ``` The following sample demonstrates the need to use packing and alignment controls; without the attribute, in 64-bit code, the fields of the structure are not placed at the locations that the kernel expects. ``` #include #include #include #include #include #include #include /* The alignment and packing attribute is necessary in 64-bit code */ struct AttrListTimes { u_int32_t length; struct timespec st_crtime; struct timespec st_modtime; } __attribute__((aligned(4), packed)); main(int argc, char **argv) { int rv; int i; for (i = 1; i < argc; i++) { struct attrlist attrList; struct AttrListTimes myStat = {0}; char *path = argv[i]; memset(&attrList, 0, sizeof(attrList)); attrList.bitmapcount = ATTR_BIT_MAP_COUNT; attrList.commonattr = ATTR_CMN_CRTIME | ATTR_CMN_MODTIME; rv = getattrlist(path, &attrList, &myStat, sizeof(myStat), 0); if (rv == -1) { warn("getattrlist(%s)", path); continue; } printf("%s: Modification time = %s", argv[i], ctime(&myStat.st_modtime.tv_sec)); } return 0; } ``` The getLinkIDInfo() function determines if ATTR\_CMNEXT\_LINKID and ATTR\_CMN\_OBJID\ are valid to use on the file system specified by path. ``` int getLinkIDInfo(const char *path, bool *cmnExtLinkIDValid, bool *cmnObjIDValid) { int result; struct statfs statfsBuf; struct attrlist attrList; struct volAttrsBuf { u_int32_t length; vol_capabilities_attr_t capabilities; vol_attributes_attr_t attributes; } __attribute__((aligned(4), packed)); struct volAttrsBuf volAttrs; memset(&attrList, 0, sizeof(attrList)); attrList.bitmapcount = ATTR_BIT_MAP_COUNT; attrList.volattr = ATTR_VOL_INFO | ATTR_VOL_CAPABILITIES | ATTR_VOL_ATTRIBUTES; // get the file system's mount point path for the input path result = statfs(path, &statfsBuf); if ( result == 0 ) { // get the supported capabilities and attributes result = getattrlist(statfsBuf.f_mntonname, &attrList, &volAttrs, sizeof(volAttrs), FSOPT_ATTR_CMN_EXTENDED); if ( result == 0 ) { if ( volAttrs.attributes.validattr.forkattr & ATTR_CMNEXT_LINKID ) { // ATTR_CMNEXT_LINKID is available; do not use ATTR_CMN_OBJID *cmnExtLinkIDValid = true; *cmnObjIDValid = false; } else { // ATTR_CMNEXT_LINKID is not available cmnExtLinkIDValid = false; // ATTR_CMN_OBJID can only be used if the file system does not use 64-bit object IDs if ( (volAttrs.capabilities.capabilities[VOL_CAPABILITIES_FORMAT] & VOL_CAP_FMT_64BIT_OBJECT_IDS) && (volAttrs.capabilities.valid[VOL_CAPABILITIES_FORMAT] & VOL_CAP_FMT_64BIT_OBJECT_IDS) ) { *cmnObjIDValid = false; } else { *cmnObjIDValid = true; } } } } if ( result != 0 ) { *cmnExtLinkIDValid = *cmnObjIDValid = false; } return result; } ``` ## SEE ALSO [access(2)](/access/2.md), [chflags(2)](/chflags/2.md), [exchangedata(2)](/exchangedata/2.md), [fcntl(2)](/fcntl/2.md), [getattrlistbulk(2)](/getattrlistbulk/2.md), [mount(2)](/mount/2.md), [searchfs(2)](/searchfs/2.md), [setattrlist(2)](/setattrlist/2.md), [stat(2)](/stat/2.md), [statfs(2)](/statfs/2.md) ## HISTORY A **getattrlist**() function call appeared in Darwin 1.3.1 (Mac OS X version 10.0). The **getattrlistat**() function call appeared in OS X 10.10 .