[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 April 19, 1994
.Dt STAT 2
.Os BSD 4
.Sh NAME
.Nm stat ,
.Nm lstat ,
.Nm fstat
.Nd get file status
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <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.
.Pp
.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.
Unlike other filesystem objects,
symbolic links do not have an owner, group, access mode, times, etc.
Instead, these attributes are taken from the directory that
contains the link.
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 fd .
.Pp
The
.Fa sb
argument is a pointer to a
.Fn stat
structure
as defined by
.Aq Pa sys/stat.h
(shown below)
and into which information is placed concerning the file.
.Bd -literal
struct stat {
    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 or 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
The time-related fields of
.Fa struct stat
are as follows:
.Bl -tag -width XXXst_mtime
.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.
.El
.Pp
The size-related fields of the
.Fa struct stat
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 .
.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:
.Bl -tag -width Er
.It Bq Er ENOTDIR
A component of the path prefix is not a directory.
.It Bq Er ENAMETOOLONG
A component of a pathname exceeded 
.Dv {NAME_MAX}
characters, or an entire path name exceeded 
.Dv {PATH_MAX}
characters.
.It Bq Er ENOENT
The named file does not exist.
.It Bq Er EACCES
Search permission is denied for a component of the path prefix.
.It Bq Er ELOOP
Too many symbolic links were encountered in translating the pathname.
.It Bq Er EFAULT
.Fa Sb
or
.Em name
points to an invalid address.
.It Bq Er EIO
An I/O error occurred while reading from or writing to the file system.
.El
.Pp
.Bl -tag -width Er
.Fn Fstat
will fail if:
.It Bq Er EBADF
.Fa fd
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 occurred while reading from or writing to the file system.
.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 SEE ALSO
.Xr chmod 2 ,
.Xr chown 2 ,
.Xr utimes 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 .
.Sh HISTORY
An
.Fn lstat
function call appeared in
.Bx 4.2 .
Commit	Line	Data
9bccf70c A	1	.\" $OpenBSD: stat.2,v 1.3 1997/02/13 05:20:55 millert Exp $
	2	.\"
	3	.\" Copyright (c) 1980, 1991, 1993, 1994
	4	.\" The Regents of the University of California. All rights reserved.
	5	.\"
	6	.\" Redistribution and use in source and binary forms, with or without
	7	.\" modification, are permitted provided that the following conditions
	8	.\" are met:
	9	.\" 1. Redistributions of source code must retain the above copyright
	10	.\" notice, this list of conditions and the following disclaimer.
	11	.\" 2. Redistributions in binary form must reproduce the above copyright
	12	.\" notice, this list of conditions and the following disclaimer in the
	13	.\" documentation and/or other materials provided with the distribution.
	14	.\" 3. All advertising materials mentioning features or use of this software
	15	.\" must display the following acknowledgement:
	16	.\" This product includes software developed by the University of
	17	.\" California, Berkeley and its contributors.
	18	.\" 4. Neither the name of the University nor the names of its contributors
	19	.\" may be used to endorse or promote products derived from this software
	20	.\" without specific prior written permission.
	21	.\"
	22	.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	23	.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	24	.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	25	.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	26	.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	27	.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	28	.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	29	.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	30	.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	31	.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	32	.\" SUCH DAMAGE.
	33	.\"
	34	.\" @(#)stat.2 8.3 (Berkeley) 4/19/94
	35	.\"
	36	.Dd April 19, 1994
	37	.Dt STAT 2
	38	.Os BSD 4
	39	.Sh NAME
	40	.Nm stat ,
	41	.Nm lstat ,
	42	.Nm fstat
	43	.Nd get file status
	44	.Sh SYNOPSIS
	45	.Fd #include <sys/types.h>
	46	.Fd #include <sys/stat.h>
	47	.Ft int
	48	.Fn stat "const char path" "struct stat sb"
	49	.Ft int
	50	.Fn lstat "const char path" "struct stat sb"
	51	.Ft int
	52	.Fn fstat "int fd" "struct stat *sb"
	53	.Sh DESCRIPTION
	54	The
	55	.Fn stat
	56	function obtains information about the file pointed to by
	57	.Fa path .
	58	Read, write or execute
	59	permission of the named file is not required, but all directories
	60	listed in the path name leading to the file must be searchable.
	61	.Pp
	62	.Fn Lstat
	63	is like
	64	.Fn stat
65	except in the case where the named file is a symbolic link,
66	in which case
67	.Fn lstat
68	returns information about the link,
69	while
70	.Fn stat
71	returns information about the file the link references.
72	Unlike other filesystem objects,
73	symbolic links do not have an owner, group, access mode, times, etc.
74	Instead, these attributes are taken from the directory that
75	contains the link.
76	The only attributes returned from an
77	.Fn lstat
78	that refer to the symbolic link itself are the file type (S_IFLNK),
79	size, blocks, and link count (always 1).
80	.Pp
81	The
82	.Fn fstat
83	obtains the same information about an open file
84	known by the file descriptor
85	.Fa fd .
86	.Pp
87	The
88	.Fa sb
89	argument is a pointer to a
90	.Fn stat
91	structure
92	as defined by
93	.Aq Pa sys/stat.h
94	(shown below)
95	and into which information is placed concerning the file.
96	.Bd -literal
97	struct stat {
98	dev_t st_dev; /* device inode resides on */
99	ino_t st_ino; /* inode's number */
100	mode_t st_mode; /* inode protection mode */
101	nlink_t st_nlink; /* number or hard links to the file */
102	uid_t st_uid; /* user-id of owner */
103	gid_t st_gid; /* group-id of owner */
104	dev_t st_rdev; /* device type, for special file inode */
105	struct timespec st_atimespec; /* time of last access */
106	struct timespec st_mtimespec; /* time of last data modification */
107	struct timespec st_ctimespec; /* time of last file status change */
108	off_t st_size; /* file size, in bytes */
109	quad_t st_blocks; /* blocks allocated for file */
110	u_long st_blksize;/* optimal file sys I/O ops blocksize */
111	u_long st_flags; /* user defined flags for file */
112	u_long st_gen; /* file generation number */
113	};
114	.Ed
115	.Pp
116	The time-related fields of
117	.Fa struct stat
118	are as follows:
119	.Bl -tag -width XXXst_mtime
120	.It st_atime
121	Time when file data last accessed.
122	Changed by the
123	.Xr mknod 2 ,
124	.Xr utimes 2
125	and
126	.Xr read 2
127	system calls.
128	.It st_mtime
129	Time when file data last modified.
130	Changed by the
131	.Xr mknod 2 ,
132	.Xr utimes 2
133	and
134	.Xr write 2
135	system calls.
136	.It st_ctime
137	Time when file status was last changed (inode data modification).
138	Changed by the
139	.Xr chmod 2 ,
140	.Xr chown 2 ,
141	.Xr link 2 ,
142	.Xr mknod 2 ,
143	.Xr rename 2 ,
144	.Xr unlink 2 ,
145	.Xr utimes 2
146	and
147	.Xr write 2
148	system calls.
149	.El
150	.Pp
151	The size-related fields of the
152	.Fa struct stat
153	are as follows:
154	.Bl -tag -width XXXst_blksize
155	.It st_blksize
156	The optimal I/O block size for the file.
157	.It st_blocks
158	The actual number of blocks allocated for the file in 512-byte units.
159	As short symbolic links are stored in the inode, this number may
160	be zero.
161	.El
162	.Pp
163	The status information word
164	.Fa st_mode
165	has the following bits:
166	.Bd -literal
167	#define S_IFMT 0170000 /* type of file */
168	#define S_IFIFO 0010000 /* named pipe (fifo) */
169	#define S_IFCHR 0020000 /* character special */
170	#define S_IFDIR 0040000 /* directory */
171	#define S_IFBLK 0060000 /* block special */
172	#define S_IFREG 0100000 /* regular */
173	#define S_IFLNK 0120000 /* symbolic link */
174	#define S_IFSOCK 0140000 /* socket */
175	#define S_IFWHT 0160000 /* whiteout */
176	#define S_ISUID 0004000 /* set user id on execution */
177	#define S_ISGID 0002000 /* set group id on execution */
178	#define S_ISVTX 0001000 /* save swapped text even after use */
179	#define S_IRUSR 0000400 /* read permission, owner */
180	#define S_IWUSR 0000200 /* write permission, owner */
181	#define S_IXUSR 0000100 /* execute/search permission, owner */
182	.Ed
183	.Pp
184	For a list of access modes, see
185	.Aq Pa sys/stat.h ,
186	.Xr access 2
187	and
188	.Xr chmod 2 .
189	.Sh RETURN VALUES
190	Upon successful completion a value of 0 is returned.
191	Otherwise, a value of -1 is returned and
192	.Va errno
193	is set to indicate the error.
194	.Sh COMPATIBILITY
195	Previous versions of the system used different types for the
196	.Li st_dev ,
197	.Li st_uid ,
198	.Li st_gid ,
199	.Li st_rdev ,
200	.Li st_size ,
201	.Li st_blksize
202	and
203	.Li st_blocks
204	fields.
205	.Sh ERRORS
206	.Fn Stat
207	and
208	.Fn lstat
209	will fail if:
210	.Bl -tag -width Er
211	.It Bq Er ENOTDIR
212	A component of the path prefix is not a directory.
213	.It Bq Er ENAMETOOLONG
214	A component of a pathname exceeded
215	.Dv {NAME_MAX}
216	characters, or an entire path name exceeded
217	.Dv {PATH_MAX}
218	characters.
219	.It Bq Er ENOENT
220	The named file does not exist.
221	.It Bq Er EACCES
222	Search permission is denied for a component of the path prefix.
223	.It Bq Er ELOOP
224	Too many symbolic links were encountered in translating the pathname.
225	.It Bq Er EFAULT
226	.Fa Sb
227	or
228	.Em name
229	points to an invalid address.
230	.It Bq Er EIO
231	An I/O error occurred while reading from or writing to the file system.
232	.El
233	.Pp
234	.Bl -tag -width Er
235	.Fn Fstat
236	will fail if:
237	.It Bq Er EBADF
238	.Fa fd
239	is not a valid open file descriptor.
240	.It Bq Er EFAULT
241	.Fa Sb
242	points to an invalid address.
243	.It Bq Er EIO
244	An I/O error occurred while reading from or writing to the file system.
245	.El
246	.Sh CAVEATS
247	The file generation number,
248	.Fa st_gen ,
249	is only available to the super-user.
250	.br
251	The fields in the stat structure currently marked
252	.Fa st_spare1 ,
253	.Fa st_spare2 ,
254	and
255	.Fa st_spare3
256	are present in preparation for inode time stamps expanding
257	to 64 bits. This, however, can break certain programs that
258	depend on the time stamps being contiguous (in calls to
259	.Xr utimes 2 ) .
260	.Sh SEE ALSO
261	.Xr chmod 2 ,
262	.Xr chown 2 ,
263	.Xr utimes 2
264	.Xr symlink 7
265	.Sh BUGS
266	Applying
267	.Xr fstat
268	to a socket (and thus to a pipe)
269	returns a zero'd buffer,
270	except for the blocksize field,
271	and a unique device and inode number.
272	.Sh STANDARDS
273	The
274	.Fn stat
275	and
276	.Fn fstat
277	function calls are expected to conform to
278	.St -p1003.1-88 .
279	.Sh HISTORY
280	An
281	.Fn lstat
282	function call appeared in
283	.Bx 4.2 .