xnu-3248.20.55.tar.gz

[apple/xnu.git] / bsd / man / man2 / stat.2

.\"	$OpenBSD: stat.2,v 1.3 1997/02/13 05:20:55 millert Exp $
.\"
.\" Copyright (c) 1980, 1991, 1993, 1994
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
.\"	California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"     @(#)stat.2	8.3 (Berkeley) 4/19/94
.\"
.Dd May 15, 2008
.Dt STAT 2
.Os BSD 4
.Sh NAME
.Nm fstat ,
.Nm fstat64 ,
.Nm lstat ,
.Nm lstat64 ,
.Nm stat ,
.Nm stat64 ,
.Nm fstatat
.Nd get file status
.Sh SYNOPSIS
.Fd #include <sys/stat.h>
.Ft int
.Fo fstat
.Fa "int fildes"
.Fa "struct stat *buf"
.Fc
.Ft int
.Fo lstat
.Fa "const char *restrict path"
.Fa "struct stat *restrict buf"
.Fc
.Ft int
.Fo stat
.Fa "const char *restrict path"
.Fa "struct stat *restrict buf"
.Fc
.Ft int
.Fn fstatat "int fd" "const char *path" "struct stat *buf" "int flag"
.Sh TRANSITIIONAL SYNOPSIS (NOW DEPRECATED)
.Ft int
.br
.Fo fstat64
.Fa "int fildes"
.Fa "struct stat64 *buf"
.Fc ;
.sp
.Ft int
.br
.Fo lstat64
.Fa "const char *restrict path"
.Fa "struct stat64 *restrict buf"
.Fc ;
.sp
.Ft int
.br
.Fo stat64
.Fa "const char *restrict path"
.Fa "struct stat64 *restrict buf"
.Fc ;
.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.
.Pp
The
.Fn lstat
function
is like
.Fn stat
except in the case where the named file is a symbolic link;
.Fn lstat
returns information about the link,
while
.Fn stat
returns information about the file the link references.
The attributes cannot be relied on in case of symbolic links.
In this case, the only attributes returned from an
.Fn lstat
that refer to the symbolic link itself are the file type (S_IFLNK),
size, blocks, and link count (always 1).
.Pp
The
.Fn fstat
obtains the same information about an open file
known by the file descriptor
.Fa fildes .
.Pp
The
.Fn fstatat
system call is equivalent to
.Fn stat
and
.Fn lstat
except in the case where the
.Fa path
specifies a relative path.
In this case the status is retrieved from a file relative to
the directory associated with the file descriptor
.Fa fd
instead of the current working directory.
.Pp
The values for the
.Fa flag
are constructed by a bitwise-inclusive OR of flags from the following list,
defined in
.In fcntl.h :
.Bl -tag -width indent
.It Dv AT_SYMLINK_NOFOLLOW
If
.Fa path
names a symbolic link, the status of the symbolic link is returned.
.El
.Pp
If
.Fn fstatat
is passed the special value
.Dv AT_FDCWD
in the
.Fa fd
parameter, the current working directory is used and the behavior is
identical to a call to
.Fn stat
or
.Fn lstat
respectively, depending on whether or not the
.Dv AT_SYMLINK_NOFOLLOW
bit is set in
.Fa flag .
.Pp
The
.Fa buf
argument is a pointer to a
.Fa stat
structure 
as defined by
.Aq Pa sys/stat.h
and into which information is placed concerning the file.
When the macro
.Dv _DARWIN_FEATURE_64_BIT_INODE
is not defined (see below for more information about this macro), the
.Fa stat
structure is defined as:
.Bd -literal
struct stat { /* when _DARWIN_FEATURE_64_BIT_INODE is NOT defined */
    dev_t    st_dev;    /* device inode resides on */
    ino_t    st_ino;    /* inode's number */
    mode_t   st_mode;   /* inode protection mode */
    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 special file inode */
    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 */
    off_t    st_size;   /* file size, in bytes */
    quad_t   st_blocks; /* blocks allocated for file */
    u_long   st_blksize;/* optimal file sys I/O ops blocksize */
    u_long   st_flags;  /* user defined flags for file */
    u_long   st_gen;    /* file generation number */
};
.Ed
.Pp
However, when the macro
.Dv _DARWIN_FEATURE_64_BIT_INODE
is defined, the
.Fa stat
structure will now be defined as:
.Bd -literal
struct stat { /* when _DARWIN_FEATURE_64_BIT_INODE is defined */
    dev_t           st_dev;           /* ID of device containing file */
    mode_t          st_mode;          /* Mode of file (see below) */
    nlink_t         st_nlink;         /* Number of hard links */
    ino_t 	    st_ino;           /* File serial number */
    uid_t           st_uid;           /* User ID of the file */
    gid_t           st_gid;           /* Group ID of the file */
    dev_t           st_rdev;          /* Device ID */
    struct timespec st_atimespec;     /* time of last access */
    struct timespec st_mtimespec;     /* time of last data modification */
    struct timespec st_ctimespec;     /* time of last status change */
    struct timespec st_birthtimespec; /* time of file creation(birth) */
    off_t           st_size;          /* file size, in bytes */
    blkcnt_t        st_blocks;        /* blocks allocated for file */
    blksize_t       st_blksize;       /* optimal blocksize for I/O */
    uint32_t        st_flags;         /* user defined flags for file */
    uint32_t        st_gen;           /* file generation number */
    int32_t         st_lspare;        /* RESERVED: DO NOT USE! */
    int64_t         st_qspare[2];     /* RESERVED: DO NOT USE! */
};
.Ed
.Pp
The time-related fields of
.Fa struct stat
are as follows:
.Bl -tag -width XXXst_birthtime
.It st_atime
Time when file data last accessed.
Changed by the
.Xr mknod 2 ,
.Xr utimes 2
and
.Xr read 2
system calls.
.It st_mtime
Time when file data last modified.
Changed by the
.Xr mknod 2 ,
.Xr utimes 2
and
.Xr write 2
system calls.
.It st_ctime
Time when file status was last changed (inode data modification).
Changed by the
.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.
.It st_birthtime
Time of file creation. Only set once when the file is created. This field is 
only available in the 64 bit inode variants. On filesystems where birthtime is 
not available, this field is set to 0 (i.e. epoch).
.El
.Pp
The size-related fields of the structures are as follows:
.Bl -tag -width XXXst_blksize
.It st_blksize
The optimal I/O block size for the file.
.It 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
.Pp
The status information word
.Fa st_mode
has the following bits:
.Bd -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 */
.Ed
.Pp
For a list of access modes, see
.Aq Pa sys/stat.h ,
.Xr access 2
and
.Xr chmod 2 .
.Pp
For a list of the file flags in the
.Fa st_flags
field, see
.Aq Pa sys/stat.h
and
.Xr chflags 2 .
.Sh _DARWIN_FEATURE_64_BIT_INODE
In order to accommodate advanced capabilities of newer file systems, the 
.Fa struct stat ,
.Fa struct statfs ,
and
.Fa struct dirent
data structures were updated in Mac OSX 10.5.
.Pp
The most obvious change is the increased size of
.Fa ino_t
from 32 bits to 64 bits.  As a consequence, storing an ino_t in an int is
no longer safe, and file formats storing ino_t as 32-bit values may need to
be updated.  There are other changes as well, such as the widening of
.Fa f_fstypename ,
.Fa f_mntonname ,
and
.Fa f_mntfromname
in
.Fa struct statfs .
Please refer to
.Xr stat 2
and
.Xr dir 5
for more detail on the specific changes to the other affected data structures.
.Pp
On platforms that existed before these updates were available, ABI
compatibility is achieved by providing two implementations for related
functions: one using the legacy data structures and one using the updated
data structures.  Variants which make use of the newer structures have their
symbols suffixed with $INODE64.  These $INODE64 suffixes are automatically
appended by the compiler tool-chain and should not be used directly.
.Pp
Platforms that were released after these updates only have the newer variants
available to them.  These platforms have the macro
.Dv _DARWIN_FEATURE_ONLY_64_BIT_INODE
defined.
.Pp
The
.Dv _DARWIN_FEATURE_64_BIT_INODE
macro should not be set directly.  Instead, developers should make use of the
.Dv _DARWIN_NO_64_BIT_INODE
or
.Dv _DARWIN_USE_64_BIT_INODE
macros when the default variant is not desired.  The following table details
the effects of defining these macros for different deployment targets.
.Pp
.TS
center;
c s s s
l | c s s
c | c c c
c | c c c
l | c c c.
T{
.Dv _DARWIN_FEATURE_ONLY_64_BIT_INODE Sy not defined
T}
=
	Deployment Target
user defines:	< 10.5	10.5	> 10.5
_
T{
.Em (none)
T}	32-bit	32-bit	64-bit
T{
.Dv _DARWIN_NO_64_BIT_INODE
T}	32-bit	32-bit	32-bit
T{
.Dv _DARWIN_USE_64_BIT_INODE
T}	32-bit	64-bit	64-bit
_
.T&
c s s s
c s s s
c | l s s
c | c c c
l | c c c.

T{
.Dv _DARWIN_FEATURE_ONLY_64_BIT_INODE Sy defined
T}
=
user defines:	Any Deployment Target
_
T{
.Em (none)
T}	64-bit-only
T{
.Dv _DARWIN_NO_64_BIT_INODE
T}	T{
.Em (error)
T}
T{
.Dv _DARWIN_USE_64_BIT_INODE
T}	64-bit-only
_
.TE
.Pp
.Bl -tag -width 64-bit-only -offset indent
.It 32-bit
32-bit inode values are enabled, and the legacy structures involving the
.Vt ino_t
type are in use.
The macro
.Dv _DARWIN_FEATURE_64_BIT_INODE
is not defined.
.It 64-bit
64-bit inode values are enabled, and the expanded structures involving the
.Vt ino_t
type are in use.
The macro
.Dv _DARWIN_FEATURE_64_BIT_INODE
is defined, and loader symbols will contain the
.Li $INODE64
suffix.
.It 64-bit-only
Like 64-bit, except loader symbols do not have the
.Li $INODE64
suffix.
.It Em (error)
A compile time error is generated.
.El
.Pp
Due to the increased benefits of the larger structure, it is highly
recommended that developers not define
.Dv _DARWIN_NO_64_BIT_INODE
and make use of
.Dv _DARWIN_USE_64_BIT_INODE
when targeting Mac OSX 10.5.
.Pp
In addition to the $INODE64 suffixed symbols, variants suffixed with 64 are
also available for related functions.  These functions were provided as a way
for developers to use the updated structures in code that also made use of
the legacy structures.  The enlarged stat structures were also prefixed with
64 to distinguish them from their legacy variants.  These functions have been
deprecated and should be avoided.
.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
.Bl -tag -width Er
The
.Fn fstat
system call will fail if:
.\" ===========
.It Bq Er EBADF
.Fa fildes
is not a valid open file descriptor.
.\" ===========
.It Bq Er EFAULT
.Fa Sb
points to an invalid address.
.\" ===========
.It Bq Er EIO
An I/O error occurs while reading from or writing to the file system.
.El
.Pp
The
.Fn lstat
and
.Fn stat
system calls will fail if:
.Bl -tag -width Er
.\" ===========
.It Bq Er EACCES
Search permission is denied for a component of the path prefix.
.\" ===========
.It Bq Er EFAULT
.Fa Sb
or
.Em name
points to an invalid address.
.\" ===========
.It Bq Er EIO
An I/O error occurs while reading from or writing to the file system.
.\" ===========
.It Bq Er ELOOP
Too many symbolic links are encountered in translating the pathname.
This is taken to be indicative of a looping symbolic link.
.\" ===========
.It Bq Er ENAMETOOLONG
A component of a pathname exceeds
.Dv {NAME_MAX}
characters, or an entire path name exceeds
.Dv {PATH_MAX}
characters.
.\" ===========
.It Bq Er ENOENT
The named file does not exist.
.\" ===========
.It Bq Er ENOTDIR
A component of the path prefix is not a directory.
.El
.Pp
The
.Fn fstat ,
.Fn lstat ,
and
.Fn stat
system calls will fail if:
.Bl -tag -width Er
.\" ===========
.It Bq Er EOVERFLOW
The file size in bytes 
or the number of blocks allocated to the file
or the file serial number cannot be represented correctly
in the structure pointed to by
.Fa buf .
.El
.Pp
In addition to the errors returned by the
.Fn stat
and
.Fn lstat ,
.Fn fstatat
may fail if:
.Bl -tag -width Er
.It Bq Er EBADF
The
.Fa path
argument does not specify an absolute path and the
.Fa fd
argument is neither
.Dv AT_FDCWD
nor a valid file descriptor open for searching.
.It Bq Er EINVAL
The value of the
.Fa flag
argument is not valid.
.It Bq Er ENOTDIR
The
.Fa path
argument is not an absolute path and
.Fa fd
is neither
.Dv AT_FDCWD
nor a file descriptor associated with a directory.
.El
.Sh CAVEATS
The file generation number,
.Fa st_gen ,
is only available to the super-user.
.br
The fields in the stat structure currently marked
.Fa st_spare1 ,
.Fa st_spare2 ,
and
.Fa st_spare3
are present in preparation for inode time stamps expanding
to 64 bits.  This, however, can break certain programs that
depend on the time stamps being contiguous (in calls to
.Xr utimes 2 ) .
.Sh TRANSITIONAL DESCRIPTION (NOW DEPRECATED)
The
.Fa fstat64 ,
.Fa lstat64
and
.Fa stat64
routines are equivalent to their corresponding non-64-suffixed routine,
when 64-bit inodes are in effect.
They were added before there was support for the symbol variants, and so are
now deprecated.
Instead of using these, set the
.Dv _DARWIN_USE_64_BIT_INODE
macro before including header files to force 64-bit inode support.
.Pp
The
.Fa stat64
structure used by these deprecated routines is the same as the
.Fa stat
structure when 64-bit inodes are in effect (see above).
.Sh SEE ALSO
.Xr chflags 2 ,
.Xr chmod 2 ,
.Xr chown 2 ,
.Xr utimes 2 ,
.Xr compat 5 ,
.Xr statfs 2 ,
.Xr symlink 7
.Sh BUGS
Applying
.Xr fstat
to a socket (and thus to a pipe)
returns a zero'd buffer,
except for the blocksize field,
and a unique device and inode number.
.Sh STANDARDS
The
.Fn stat
and
.Fn fstat
function calls are expected to conform to 
.St -p1003.1-88 .
The
.Fn fstatat
system call is expected to conform to POSIX.1-2008 .
.Sh HISTORY
An
.Fn lstat
function call appeared in
.Bx 4.2 .
The 
.Fn stat64 ,
.Fn fstat64 ,
and
.Fn lstat64
system calls first appeared in Mac OS X 10.5 (Leopard) and are now deprecated
in favor of the corresponding symbol variants.
The
.Fn fstatat
system call appeared in OS X 10.10