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STAT(2) System Calls Manual STAT(2)

fstat, fstat64, lstat, lstat64, stat, stat64, fstatat — get file status

#include <sys/stat.h>

int
fstat(int fildes, struct stat *buf);

int
lstat(const char *restrict path, struct stat *restrict buf);

int
stat(const char *restrict path, struct stat *restrict buf);

int
fstatat(int fd, const char *path, struct stat *buf, int flag);

int
(int fildes, struct stat64 *buf);;

int
(const char *restrict path, struct stat64 *restrict buf);;

int
(const char *restrict path, struct stat64 *restrict buf);;

The () function obtains information about the file pointed to by path. Read, write or execute permission of the named file is not required, but all directories listed in the path name leading to the file must be searchable.

The () function is like stat() except in the case where the named file is a symbolic link; lstat() returns information about the link, while stat() returns information about the file the link references. For symbolic links, the st_mode member contains meaningful information when used with the file type macros, and the st_size member contains the length of the pathname contained in the symbolic link. File mode bits and the contents of the remaining members of the stat structure are unspecified. The value returned in the st_size member is the length of the contents of the symbolic link, and does not count any trailing null.

The () obtains the same information about an open file known by the file descriptor fildes.

The () system call is equivalent to stat() and lstat() except in the case where the path specifies a relative path. In this case the status is retrieved from a file relative to the directory associated with the file descriptor fd instead of the current working directory.

The values for the flag are constructed by a bitwise-inclusive OR of flags from the following list, defined in <fcntl.h>:

If path names a symbolic link, the status of the symbolic link is returned.
If path names a symbolic link, the status of the symbolic link is returned. If a symbolic link is encountered during pathname resolution, an error is returned.

If () 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 stat() or lstat() respectively, depending on whether or not the AT_SYMLINK_NOFOLLOW bit is set in flag.

The buf argument is a pointer to a stat structure as defined by ⟨sys/stat.h⟩ and into which information is placed concerning the file. When the macro _DARWIN_FEATURE_64_BIT_INODE is not defined (see below for more information about this macro), the stat structure is defined as:

struct stat { /* when _DARWIN_FEATURE_64_BIT_INODE is NOT defined */
    dev_t    st_dev;    /* device inode resides on */
    ino_t    st_ino;    /* inode's number */
    mode_t   st_mode;   /* inode protection mode */
    nlink_t  st_nlink;  /* number of hard links to the file */
    uid_t    st_uid;    /* user-id of owner */
    gid_t    st_gid;    /* group-id of owner */
    dev_t    st_rdev;   /* device type, for special file inode */
    struct timespec st_atimespec;  /* time of last access */
    struct timespec st_mtimespec;  /* time of last data modification */
    struct timespec st_ctimespec;  /* time of last file status change */
    off_t    st_size;   /* file size, in bytes */
    quad_t   st_blocks; /* blocks allocated for file */
    u_long   st_blksize;/* optimal file sys I/O ops blocksize */
    u_long   st_flags;  /* user defined flags for file */
    u_long   st_gen;    /* file generation number */
};

However, when the macro _DARWIN_FEATURE_64_BIT_INODE is defined, the stat structure will now be defined as:

struct stat { /* when _DARWIN_FEATURE_64_BIT_INODE is defined */
    dev_t           st_dev;           /* ID of device containing file */
    mode_t          st_mode;          /* Mode of file (see below) */
    nlink_t         st_nlink;         /* Number of hard links */
    ino_t 	    st_ino;           /* File serial number */
    uid_t           st_uid;           /* User ID of the file */
    gid_t           st_gid;           /* Group ID of the file */
    dev_t           st_rdev;          /* Device ID */
    struct timespec st_atimespec;     /* time of last access */
    struct timespec st_mtimespec;     /* time of last data modification */
    struct timespec st_ctimespec;     /* time of last status change */
    struct timespec st_birthtimespec; /* time of file creation(birth) */
    off_t           st_size;          /* file size, in bytes */
    blkcnt_t        st_blocks;        /* blocks allocated for file */
    blksize_t       st_blksize;       /* optimal blocksize for I/O */
    uint32_t        st_flags;         /* user defined flags for file */
    uint32_t        st_gen;           /* file generation number */
    int32_t         st_lspare;        /* RESERVED: DO NOT USE! */
    int64_t         st_qspare[2];     /* RESERVED: DO NOT USE! */
};

The time-related fields of struct stat are as follows:

st_atime
Time when file data last accessed. Changed by the mknod(2), utimes(2) and read(2) system calls.
st_mtime
Time when file data last modified. Changed by the mknod(2), utimes(2) and write(2) system calls.
st_ctime
Time when file status was last changed (inode data modification). Changed by the chmod(2), chown(2), link(2), mknod(2), rename(2), unlink(2), utimes(2) and write(2) system calls.
st_birthtime
Time of file creation. Only set once when the file is created. This field is only available in the 64 bit inode variants. On filesystems where birthtime is not available, this field is set to 0 (i.e. epoch).

The size-related fields of the structures are as follows:

st_blksize
The optimal I/O block size for the file.
st_blocks
The actual number of blocks allocated for the file in 512-byte units. As short symbolic links are stored in the inode, this number may be zero.

The status information word st_mode has the following bits:

#define S_IFMT 0170000           /* type of file */
#define        S_IFIFO  0010000  /* named pipe (fifo) */
#define        S_IFCHR  0020000  /* character special */
#define        S_IFDIR  0040000  /* directory */
#define        S_IFBLK  0060000  /* block special */
#define        S_IFREG  0100000  /* regular */
#define        S_IFLNK  0120000  /* symbolic link */
#define        S_IFSOCK 0140000  /* socket */
#define        S_IFWHT  0160000  /* whiteout */
#define S_ISUID 0004000  /* set user id on execution */
#define S_ISGID 0002000  /* set group id on execution */
#define S_ISVTX 0001000  /* save swapped text even after use */
#define S_IRUSR 0000400  /* read permission, owner */
#define S_IWUSR 0000200  /* write permission, owner */
#define S_IXUSR 0000100  /* execute/search permission, owner */

For a list of access modes, see ⟨sys/stat.h⟩, access(2) and chmod(2).

For a list of the file flags in the st_flags field, see ⟨sys/stat.h⟩ and chflags(2).

In order to accommodate advanced capabilities of newer file systems, the struct stat, struct statfs, and struct dirent data structures were updated in Mac OSX 10.5.

The most obvious change is the increased size of ino_t from 32 bits to 64 bits. As a consequence, storing an ino_t in an int is no longer safe, and file formats storing ino_t as 32-bit values may need to be updated. There are other changes as well, such as the widening of f_fstypename, f_mntonname, and f_mntfromname in struct statfs. Please refer to dir(5) for more detail on the specific changes to the other affected data structures.

On platforms that existed before these updates were available, ABI compatibility is achieved by providing two implementations for related functions: one using the legacy data structures and one using the updated data structures. Variants which make use of the newer structures have their symbols suffixed with $INODE64. These $INODE64 suffixes are automatically appended by the compiler tool-chain and should not be used directly.

Platforms that were released after these updates only have the newer variants available to them. These platforms have the macro _DARWIN_FEATURE_ONLY_64_BIT_INODE defined.

The _DARWIN_FEATURE_64_BIT_INODE macro should not be set directly. Instead, developers should make use of the _DARWIN_NO_64_BIT_INODE or _DARWIN_USE_64_BIT_INODE macros when the default variant is not desired. The following table details the effects of defining these macros for different deployment targets.

_DARWIN_FEATURE_ONLY_64_BIT_INODE not defined
Deployment Target
user defines: < 10.5 10.5 > 10.5
(none) 32-bit 32-bit 64-bit
_DARWIN_NO_64_BIT_INODE 32-bit 32-bit 32-bit
_DARWIN_USE_64_BIT_INODE 32-bit 64-bit 64-bit
_DARWIN_FEATURE_ONLY_64_BIT_INODE defined
user defines: Any Deployment Target
(none) 64-bit-only
_DARWIN_NO_64_BIT_INODE (error)
_DARWIN_USE_64_BIT_INODE 64-bit-only
32-bit
32-bit inode values are enabled, and the legacy structures involving the ino_t type are in use. The macro _DARWIN_FEATURE_64_BIT_INODE is not defined.
64-bit
64-bit inode values are enabled, and the expanded structures involving the ino_t type are in use. The macro _DARWIN_FEATURE_64_BIT_INODE is defined, and loader symbols will contain the $INODE64 suffix.
64-bit-only
Like 64-bit, except loader symbols do not have the $INODE64 suffix.
A compile time error is generated.

Due to the increased benefits of the larger structure, it is highly recommended that developers not define _DARWIN_NO_64_BIT_INODE and make use of _DARWIN_USE_64_BIT_INODE when targeting Mac OSX 10.5.

In addition to the $INODE64 suffixed symbols, variants suffixed with 64 are also available for related functions. These functions were provided as a way for developers to use the updated structures in code that also made use of the legacy structures. The enlarged stat structures were also prefixed with 64 to distinguish them from their legacy variants. These functions have been deprecated and should be avoided.

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

Previous versions of the system used different types for the st_dev, st_uid, st_gid, st_rdev, st_size, st_blksize and st_blocks fields.

The fstat() system call will fail if:

[]
fildes is not a valid open file descriptor.
[]
Sb points to an invalid address.
[]
An I/O error occurs while reading from or writing to the file system.

The lstat() and stat() system calls will fail if:

[]
Search permission is denied for a component of the path prefix.
[]
Sb or points to an invalid address.
[]
An I/O error occurs while reading from or writing to the file system.
[]
Too many symbolic links are encountered in translating the pathname. This is taken to be indicative of a looping symbolic link.
[]
If AT_SYMLINK_NOFOLLOW_ANY is passed and symbolic link was encountered during pathname resolution.
[]
A component of a pathname exceeds {NAME_MAX} characters, or an entire path name exceeds {PATH_MAX} characters.
[]
The named file does not exist.
[]
A component of the path prefix is not a directory.

The fstat(), lstat(), and stat() system calls will fail if:

[]
The file size in bytes or the number of blocks allocated to the file or the file serial number cannot be represented correctly in the structure pointed to by buf.

In addition to the errors returned by the stat() and lstat(), fstatat() 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 value of the flag argument is not valid.
[]
The path argument is not an absolute path and fd is neither AT_FDCWD nor a file descriptor associated with a directory.

The file generation number, st_gen, is only available to the super-user.
The fields in the stat structure currently marked st_spare1, st_spare2, and st_spare3 are present in preparation for inode time stamps expanding to 64 bits. This, however, can break certain programs that depend on the time stamps being contiguous (in calls to utimes(2)).

The fstat64, lstat64 and stat64 routines are equivalent to their corresponding non-64-suffixed routine, when 64-bit inodes are in effect. They were added before there was support for the symbol variants, and so are now deprecated. Instead of using these, set the _DARWIN_USE_64_BIT_INODE macro before including header files to force 64-bit inode support.

The stat64 structure used by these deprecated routines is the same as the stat structure when 64-bit inodes are in effect (see above).

chflags(2), chmod(2), chown(2), statfs(2), utimes(2), compat(5), symlink(7)

Applying fstat() to a socket (and thus to a pipe) returns a zero'd buffer, except for the blocksize field, and a unique device and inode number.

The stat() and fstat() function calls are expected to conform to IEEE Std 1003.1-1988 (“POSIX.1”). The fstatat() system call is expected to conform to POSIX.1-2008 .

An lstat() function call appeared in 4.2BSD. The stat64(), fstat64(), and lstat64() system calls first appeared in Mac OS X 10.5 (Leopard) and are now deprecated in favor of the corresponding symbol variants. The fstatat() system call appeared in OS X 10.10

May 15, 2008 macOS-15.5.0