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DESCRIPTION

The lstat() system call is like stat() except when the named file is a symbolic link, in which case lstat() returns information about the link, while stat() returns information about the file the link references.

The fstat() system call obtains the same information about an open file known by the file descriptor fd.

The fstatat() system call is equivalent to stat() and lstat() except when 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 this list, defined in <fcntl.h>:

AT_SYMLINK_NOFOLLOW

If path names a symbolic link, the status of the symbolic link is returned.

If fstatat() 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 sb argument is a pointer to a stat structure as defined by <sys/stat.h> and into which information is placed concerning the file.

The fields of struct stat related to the file system are:

st_dev

Numeric ID of the device containing the file.

st_ino

The file's inode number.

st_nlink

Number of hard links to the file.

st_flags

Flags enabled for the file. See chflags(2) for the list of flags and their description.

The st_dev and st_ino fields together identify the file uniquely within the system.

The time-related fields of struct stat are:

st_atim

Time when file data was last accessed. Changed by the mknod(2), utimes(2), read(2) and readv(2) system calls.

st_mtim

Time when file data was last modified. Changed by the mkdir(2), mkfifo(2), mknod(2), utimes(2), write(2) and writev(2) system calls.

st_ctim

Time when file status was last changed (inode data modification). Changed by the chflags(2), chmod(2), chown(2), creat(2), link(2), mkdir(2), mkfifo(2), mknod(2), rename(2), rmdir(2), symlink(2), truncate(2), unlink(2), utimes(2), write(2) and writev(2) system calls.

st_birthtim

Time when the inode was created.

These time-related macros are defined for compatibility:

#define	st_atime		st_atim.tv_sec
#define	st_mtime		st_mtim.tv_sec
#define	st_ctime		st_ctim.tv_sec
#ifndef _POSIX_SOURCE
#define	st_birthtime		st_birthtim.tv_sec
#endif

#ifndef _POSIX_SOURCE
#define	st_atimespec		st_atim
#define	st_mtimespec		st_mtim
#define	st_ctimespec		st_ctim
#define	st_birthtimespec	st_birthtim
#endif

Size-related fields of the struct stat are:

st_size

File size in bytes.

st_blksize

Optimal I/O block size for the file.

st_blocks

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 access-related fields of struct stat are:

st_uid

User ID of the file's owner.

st_gid

Group ID of the file.

st_mode

Status of the file (see below).

The status information word st_mode has these bits:

#define S_IFMT   0170000  /* type of file mask */
#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_IRWXU  0000700  /* RWX mask for owner */
#define S_IRUSR  0000400  /* read permission, owner */
#define S_IWUSR  0000200  /* write permission, owner */
#define S_IXUSR  0000100  /* execute/search permission, owner */
#define S_IRWXG  0000070  /* RWX mask for group */
#define S_IRGRP  0000040  /* read permission, group */
#define S_IWGRP  0000020  /* write permission, group */
#define S_IXGRP  0000010  /* execute/search permission, group */
#define S_IRWXO  0000007  /* RWX mask for other */
#define S_IROTH  0000004  /* read permission, other */
#define S_IWOTH  0000002  /* write permission, other */
#define S_IXOTH  0000001  /* execute/search permission, other */

For a list of access modes, see <sys/stat.h>, access(2) and chmod(2). These macros are available to test whether a st_mode value passed in the m argument corresponds to a file of the specified type:

S_ISBLK(m)

Test for a block special file.

S_ISCHR(m)

Test for a character special file.

S_ISDIR(m)

Test for a directory.

S_ISFIFO(m)

Test for a pipe or FIFO special file.

S_ISLNK(m)

Test for a symbolic link.

S_ISREG(m)

Test for a regular file.

S_ISSOCK(m)

Test for a socket.

S_ISWHT(m)

Test for a whiteout.

The macros evaluate to a non-zero value if the test is true or to the value 0 if the test is false.