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.
The lstat() function is identical to stat() except when the
named file is
a symbolic link, in which case lstat() returns information
about the link
itself, not the file the link references. Unlike other file
system 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() function 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's 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 */
int64_t st_blocks; /* blocks allocated for file */
u_int32_t st_blksize;/* optimal file sys I/O ops blocksize */
u_int32_t st_flags; /* user defined flags for file */
u_int32_t st_gen; /* file generation number */
};
The time-related fields of struct stat are as follows:
st_atime Time when file data was last accessed. Changed
by the
mknod(2), utimes(2), and read(2) system calls.
st_mtime Time when file data was 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.
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.
chmod(2), chown(2), utimes(2), symlink(7)
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 stat() and fstat() function calls are expected to conform to IEEE Std
1003.1-1988 (``POSIX'').
A stat() function appeared in Version 2 AT&T UNIX. An
lstat() function
call appeared in 4.2BSD.
The file generation number, st_gen, is only available to the
superuser.
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)).
Applying fstat() to a socket (and thus to a pipe) returns a
zeroed
buffer, except for the blocksize field, and a unique device
and inode
number.
OpenBSD 3.6 April 19, 1994
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