STAT(2) BSD System Calls Manual STAT(2)NAME
stat, lstat, fstat — 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);
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 refer‐
ences. 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> 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
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 fol‐
lowing 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
Upon successful completion a value of 0 is returned. Otherwise, a value
of -1 is returned and 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.
ERRORSstat() and lstat() 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 name 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 translat‐
ing the pathname.
[ENAMETOOLONG] A component of a pathname exceeded {NAME_MAX} charac‐
ters, or an entire path name exceeded {PATH_MAX} char‐
acters.
[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.
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 ALSOchflags(2), chmod(2), chown(2), utimes(2), dirent(3), types(3),
symlink(7)STANDARDS
The described functions conform to IEEE Std 1003.1-2004 (“POSIX.1”).
HISTORY
A stat() function call appeared in Version 2 AT&T UNIX. A lstat() func‐
tion call appeared in 4.2BSD.
BUGS
Applying fstat() to a socket (and thus to a pipe) returns a zero'd buf‐
fer, except for the blocksize field, and a unique device and file serial
number.
BSD September 14, 2011 BSD