Mac OS X / Darwin man pages : lstat (2)
lstat (2)
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stat, lstat, fstat - get file status
#include <sys/types.h>
#include <sys/stat.h>
int
stat(const char *path, struct stat *sb);
int
lstat(const char *path, struct stat *sb);
int
fstat(int fd, struct stat *sb);
The stat() 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.
Lstat() is like stat() except in the case where 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.
Unlike other filesystem objects, symbolic links do not have an owner,
group, access mode, times, etc. Instead, these attributes are taken from
the directory that contains the link. The only attributes returned from
an lstat() that refer to the symbolic link itself are the file type
(S_IFLNK), size, blocks, and link count (always 1).
The fstat() obtains the same information about an open file known by the
file descriptor fd.
The sb argument is a pointer to a stat() structure as defined by
<sys/stat.h> (shown below) and into which information is placed concerning
the file.
struct stat {
- 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 or 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 */
};
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.
The size-related fields of the struct stat 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)
.
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.
Stat() and lstat() will fail if:
- [ENOTDIR]
- A component of the path prefix is not a directory.
- [ENAMETOOLONG]
- A component of a pathname exceeded {NAME_MAX} characters,
or an entire path name exceeded {PATH_MAX} characters.
- [ENOENT]
- The named file does not exist.
- [EACCES]
- Search permission is denied for a component of the
path prefix.
- [ELOOP]
- Too many symbolic links were encountered in translating
the pathname.
- [EFAULT]
- Sb or name points to an invalid address.
- [EIO]
- An I/O error occurred while reading from or writing to
the file system.
Fstat() will fail if:
- [EBADF]
- fd is not a valid open file descriptor.
- [EFAULT]
- Sb points to an invalid address.
- [EIO]
- An I/O error occurred while reading from or writing to
the file system.
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)
).
chmod(2)
, chown(2)
, utimes(2)
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'').
An lstat() function call appeared in 4.2BSD.
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