STAT(2) System Calls Manual STAT(2)
NAME
stat, lstat, fstatget 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 references. 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_block
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 to 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. A directory will be a multiple of the size of the dirent(3) structure. Some file systems (notably ZFS) return the number of entries in the directory instead of the size in bytes.
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
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.
ERRORS
stat() and lstat() will fail if:
[EACCES]
Search permission is denied for a component of the path prefix.
[EBADF]
A badly formed v-node 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 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.
 
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
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() 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.