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stat.2 revision 1.41 
 $NetBSD: stat.2,v 1.41 2010/04/03 15:48:52 jruoho Exp $

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 @(#)stat.2 8.4 (Berkeley) 5/1/95

.Dd April 3, 2010
.Dt STAT 2
.Os
.Sh NAME
.Nm stat ,
.Nm lstat ,
.Nm fstat
.Nd get file status
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
n sys/stat.h .Ft int
.Fn stat "const char *path" "struct stat *sb"
.Ft int
.Fn lstat "const char *path" "struct stat *sb"
.Ft int
.Fn fstat "int fd" "struct stat *sb"
.Sh DESCRIPTION
The
.Fn stat
function obtains information about the file pointed to by
.Fa 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.

p
.Fn lstat
is like
.Fn stat
except in the case where the named file is a symbolic link,
in which case
.Fn lstat
returns information about the link,
while
.Fn stat
returns information about the file the link references.

p
The
.Fn fstat
function obtains the same information about an open file
known by the file descriptor
.Fa fd .

p
The
.Fa sb
argument is a pointer to a
.Fa stat
structure
as defined by
n sys/stat.h (shown below)
and into which information is placed concerning the file.
d -literal struct stat {
 dev_t st_dev; /* device containing the file */
 ino_t st_ino; /* file's serial number */
 mode_t st_mode; /* file's mode (protection and type) */
 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 device special file */
#if defined(_NETBSD_SOURCE)
 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 */
#else
 time_t st_atime; /* time of last access */
 long st_atimensec; /* nsec of last access */
 time_t st_mtime; /* time of last data modification */
 long st_mtimensec; /* nsec of last data modification */
 time_t st_ctime; /* time of last file status change */
 long st_ctimensec; /* nsec of last file status change */
#endif
 off_t st_size; /* file size, in bytes */
 blkcnt_t st_blocks; /* blocks allocated for file */
 blksize_t st_blksize; /* optimal file sys I/O ops blocksize */
 uint32_t st_flags; /* user defined flags for file */
 uint32_t st_gen; /* file generation number */
#if defined(_NETBSD_SOURCE)
 struct timespec st_birthtimespec; /* time of inode creation */
#else
 time_t st_birthtime; /* time of inode creation */
 long st_birthtimensec; /* nsec of inode creation */
#endif
};
.Ed

p
The time-related fields of
.Fa struct stat
are as follows:
l -tag -width XXXst_birthtime t st_atime Time when file data was last accessed.
Changed by the
.Xr mknod 2 ,
.Xr utimes 2
and
.Xr read 2
system calls.
t st_mtime Time when file data was last modified.
Changed by the
.Xr mknod 2 ,
.Xr utimes 2
and
.Xr write 2
system calls.
t st_ctime Time when file status was last changed (file metadata modification).
Changed by the
.Xr chflags 2 ,
.Xr chmod 2 ,
.Xr chown 2 ,
.Xr link 2 ,
.Xr mknod 2 ,
.Xr rename 2 ,
.Xr unlink 2 ,
.Xr utimes 2
and
.Xr write 2
system calls.
t st_birthtime Time when the inode was created.
.El

p
If
.Dv _NETBSD_SOURCE
is defined, the time-related fields are defined as:
d -literal #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
.Ed

p
The size-related fields of the
.Fa struct stat
are as follows:
l -tag -width XXXst_blksize t st_size The size of the file in bytes.
A directory will be a multiple of the size of the
.Xr dirent 5
structure.
Some filesystems (notably ZFS) return the number of entries in the directory
instead of the size in bytes.
t st_blksize The optimal I/O block size for the file.
t 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.
.El

p
The status information word
.Fa st_mode
has the following bits:
d -literal #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 */
#define S_IRGRP 0000040 /* read permission, group */
#define S_IWGRP 0000020 /* write permission, group */
#define S_IXGRP 0000010 /* execute/search permission, group */
#define S_IROTH 0000004 /* read permission, other */
#define S_IWOTH 0000002 /* write permission, other */
#define S_IXOTH 0000001 /* execute/search permission, other */
.Ed

p
For a list of access modes, see
n sys/stat.h , .Xr access 2
and
.Xr chmod 2 .

p
The status information word
.Fa st_flags
has the following bits:
d -literal #define UF_NODUMP 0x00000001 /* do not dump file */
#define UF_IMMUTABLE 0x00000002 /* file may not be changed */
#define UF_APPEND 0x00000004 /* writes to file may only append */
#define UF_OPAQUE 0x00000008 /* directory is opaque wrt. union */
#define SF_ARCHIVED 0x00010000 /* file is archived */
#define SF_IMMUTABLE 0x00020000 /* file may not be changed */
#define SF_APPEND 0x00040000 /* writes to file may only append */
.Ed

p
For a description of the flags, see
.Xr chflags 2 .
.Sh RETURN VALUES
Upon successful completion a value of 0 is returned.
Otherwise, a value of -1 is returned and
.Va errno
is set to indicate the error.
.Sh COMPATIBILITY
Previous versions of the system used different types for the
.Li st_dev ,
.Li st_uid ,
.Li st_gid ,
.Li st_rdev ,
.Li st_size ,
.Li st_blksize
and
.Li st_blocks
fields.
.Sh ERRORS
.Fn stat
and
.Fn lstat
will fail if:
l -tag -width Er t Bq Er EACCES Search permission is denied for a component of the path prefix.
t Bq Er EBADF A badly formed v-node was encountered.
This can happen if a file system information node is incorrect.
t Bq Er EFAULT .Fa sb
or
.Em name
points to an invalid address.
t Bq Er EIO An I/O error occurred while reading from or writing to the file system.
t Bq Er ELOOP Too many symbolic links were encountered in translating the pathname.
t Bq Er ENAMETOOLONG A component of a pathname exceeded
.Dv { NAME_MAX }
characters, or an entire path name exceeded
.Dv { PATH_MAX }
characters.
t Bq Er ENOENT The named file does not exist.
t Bq Er ENOTDIR A component of the path prefix is not a directory.
t Bq Er ENXIO The named file is a character special or block
special file, and the device associated with this special file
does not exist.
.El

p
.Fn fstat
will fail if:
l -tag -width Er t Bq Er EBADF .Fa fd
is not a valid open file descriptor.
t Bq Er EFAULT .Fa sb
points to an invalid address.
t Bq Er EIO An I/O error occurred while reading from or writing to the file system.
.El
.Sh SEE ALSO
.Xr chflags 2 ,
.Xr chmod 2 ,
.Xr chown 2 ,
.Xr utimes 2 ,
.Xr dir 5 ,
.Xr symlink 7
.Sh STANDARDS
The
.Fn stat
and
.Fn fstat
functions conform to
.St -p1003.1-90 .
.Sh HISTORY
A
.Fn stat
function call appeared in
.At v2 .
A
.Fn lstat
function call appeared in
x 4.2 . .Sh BUGS
Applying
.Fn 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.