NAME
stat,
lstat,
fstat,
fstatat —
get file status
LIBRARY
Standard C Library (libc, -lc)
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
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 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.
-
-
- 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_ISREG(m)
- Test for a regular file.
-
-
- S_ISLNK(m)
- Test for a symbolic link.
-
-
- S_ISSOCK(m)
- Test for a socket.
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
A
stat() function call appeared in
Version 2 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.