NAME
stat
, lstat
,
fstat
, fstatat
—
get file status
LIBRARY
library “libc”
SYNOPSIS
#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);
#include
<sys/stat.h>
#include <fcntl.h>
int
fstatat
(int
fd, const char
*path, struct stat
*sb, int flag);
DESCRIPTION
Thestat
()
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
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. The
fstat
()
function obtains the same information about an open file known by the file
descriptor fd.
fstatat
()
works the same way as stat
() (or
lstat
() if
AT_SYMLINK_NOFOLLOW
is set in
flag) except if path is
relative. In that case, it is looked up from a directory whose file
descriptor was passed as fd. Search permission is
required on this directory. fd can be set to
AT_FDCWD
in order to specify the current
directory.
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 Standard Structure
The following standards-compliant fields are defined in the structure:
Type | Entry | Description |
dev_t | st_dev | device ID containing the file |
ino_t | st_ino | serial number of the file (inode number) |
mode_t | st_mode | mode of the file |
nlink_t | st_nlink | number of hard links to the file |
uid_t | st_uid | user ID of the owner |
gid_t | st_gid | group ID of the owner |
dev_t | st_rdev | device type (character or block special) |
off_t | st_size | size of the file in bytes |
time_t | st_atime | time of last access |
time_t | st_mtime | time of last data modification |
time_t | st_ctime | time of last file status change |
blksize_t | st_blksize | preferred I/O block size (fs-specific) |
blkcnt_t | st_blocks | blocks allocated for the file |
These are specified in the IEEE Std 1003.1-2004 (“POSIX.1”) standard. The st_ino and st_dev fields taken together uniquely identify the file within the system. Most of the types are defined in types(3).
The time-related fields are:
- 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 (file metadata modification). Changed by the chflags(2), 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_size
- The size of the file in bytes. The meaning of the size reported for a directory is file system dependent. Some file systems (e.g. FFS) return the total size used for the directory metadata, possibly including free slots; others (notably ZFS) return the number of entries in the directory. Some may also return other things or always report zero.
- 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 contains bits that define the access mode (see chmod(2)) and the type (see dirent(3)) of the file. The following macros can be used to test whether a file is of the specified type. The value m supplied to the macros is the value of st_mode.
The macros evaluate to a non-zero value if the test is true or to the value 0 if the test is false.
NetBSD Extensions
The following additional NetBSD specific fields are present:
Type | Entry | Description |
long | st_atimensec | last access (nanoseconds) |
long | st_mtimensec | last modification (nanoseconds) |
long | st_ctimensec | last status change (nanoseconds) |
time_t | st_birthtime | time of inode creation |
long | st_birthtimensec | inode creation (nanoseconds) |
uint32_t | st_flags | user defined flags for the file |
uint32_t | st_gen | file generation number |
uint32_t | st_spare[2] | implementation detail |
However, if _NETBSD_SOURCE is furthermore defined, instead of the above, the following are present in the structure:
Type | Entry | Description |
struct timespec | st_atimespec | time of last access |
struct timespec | st_mtimespec | time of last modification |
struct timespec | st_birthtimespec | time of creation |
uint32_t | st_flags | user defined flags |
uint32_t | st_gen | file generation number |
uint32_t | st_spare[2] | implementation detail |
In this case the following macros are provided for convenience:
#if defined(_NETBSD_SOURCE) #define st_atime st_atimespec.tv_sec #define st_atimensec st_atimespec.tv_nsec #define st_mtime st_mtimespec.tv_sec #define st_mtimensec st_mtimespec.tv_nsec #define st_ctime st_ctimespec.tv_sec #define st_ctimensec st_ctimespec.tv_nsec #define st_birthtime st_birthtimespec.tv_sec #define st_birthtimensec st_birthtimespec.tv_nsec #endif
The status information word st_flags has the following bits:
Constant | Description |
UF_NODUMP |
do not dump a file |
UF_IMMUTABLE |
file may not be changed |
UF_APPEND |
writes to file may only append |
UF_OPAQUE |
directory is opaque wrt. union |
SF_ARCHIVED |
file is archived |
SF_IMMUTABLE |
file may not be changed |
SF_APPEND |
writes to file may only append |
For a description of the flags, see chflags(2).
RETURN VALUES
The stat
(),
lstat
(), fstat
(), and
fstatat
() functions return the value 0 if
successful; otherwise the value -1 is returned and the global
variable errno is set to indicate the error.
COMPATIBILITY
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.
ERRORS
stat
(), lstat
()
and fstatat
() will fail if:
- [
EACCES
] - Search permission is denied for a component of the path prefix.
- [
EBADF
] - A badly formed vnode was encountered. This can happen if a file system information node is incorrect.
- [
EFAULT
] - sb or path points to an invalid address.
- [
EIO
] - An I/O error occurred while reading from or writing to the file system.
- [
ELOOP
] - Too many symbolic links were encountered in translating the pathname.
- [
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.
- [
ENOTDIR
] - A component of the path prefix is not a directory.
- [
ENXIO
] - The named file is a character special or block special file, and the device associated with this special file does not exist.
In addition, fstatat
() will fail if:
- [
EBADF
] - path does not specify an absolute path and
fd is neither
AT_FDCWD
nor a valid file descriptor open for reading or searching. - [
ENOTDIR
] - path is not an absolute path and fd is a file descriptor associated with a non-directory file.
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.
SEE ALSO
chflags(2), chmod(2), chown(2), utimes(2), dirent(3), types(3), symlink(7)
STANDARDS
stat
(), lstat
(),
and fstat
() conform to IEEE Std
1003.1-2004 (“POSIX.1”).
fstatat
() conforms to IEEE Std
1003.1-2008 (“POSIX.1”).
HISTORY
The stat
() and
fstat
() function calls appeared in
Version 1 AT&T UNIX. A
lstat
() function call appeared in
4.2BSD.
BUGS
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 file serial number.