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

.\"	$NetBSD: unlink.2,v 1.7 1995/02/27 12:39:13 cgd Exp $
.\"
.\" Copyright (c) 1980, 1991, 1993
.\"	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.
.\"
.\"     @(#)unlink.2	8.1 (Berkeley) 6/4/93
.\"
.Dd June 4, 1993
.Dt UNLINK 2
.Os BSD 4
.Sh NAME
.Nm unlink ,
.Nm unlinkat
.Nd remove directory entry
.Sh SYNOPSIS
.Fd #include <unistd.h>
.Ft int
.Fo unlink
.Fa "const char *path"
.Fc
.Ft int
.Fn unlinkat "int fd" "const char *path" "int flag"
.Sh DESCRIPTION
The
.Fn unlink
function
removes the link named by
.Fa path
from its directory and decrements the link count of the
file which was referenced by the link.
If that decrement reduces the link count of the file
to zero,
and no process has the file open, then
all resources associated with the file are reclaimed.
If one or more process have the file open when the last link is removed,
the link is removed, but the removal of the file is delayed until
all references to it have been closed.
.Pp
The
.Fn unlinkat
system call is equivalent to
.Fn unlink
or
.Fn rmdir
except in the case where
.Fa path
specifies a relative path.
In this case the directory entry to be removed is determined
relative to the directory associated with the file descriptor
.Fa fd
instead of the current working directory.
.Pp
The values for
.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_REMOVEDIR
Remove the directory entry specified by
.Fa fd
and
.Fa path
as a directory, not a normal file.
.El
.Pp
If
.Fn unlinkat
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
.Fa unlink
or
.Fa rmdir
respectively, depending on whether or not the
.Dv AT_REMOVEDIR
bit is set in flag.
.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 ERRORS
The
.Fn unlink
system call 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 EACCES
Write permission is denied on the directory containing the link
to be removed.
.\" ===========
.It Bq Er EBUSY
The entry to be unlinked is the mount point for a
mounted file system.
.\" ===========
.It Bq Er EBUSY
The file named by the
.Fa path
argument cannot be unlinked
because it is being used by the system or by another process.
.\" ===========
.It Bq Er EFAULT
.Fa Path
points outside the process's allocated address space.
.\" ===========
.It Bq Er EIO
An I/O error occurs while deleting the directory entry
or deallocating the inode.
.\" ===========
.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 (possibly as a result of expanding a symlink).
.\" ===========
.It Bq Er ENOENT
The named file does not exist.
.\" ===========
.It Bq Er ENOTDIR
A component of the path prefix is not a directory.
.\" ===========
.It Bq Er EPERM
The named file is a directory and the effective user ID
of the process is not the super-user.
.\" ===========
.It Bq Er EPERM
The directory containing the file is marked sticky,
and neither the containing directory nor the file to be removed
are owned by the effective user ID.
.\" ===========
.It Bq Er EROFS
The named file resides on a read-only file system.
.El
.Pp
In addition to the errors returned by the
.Fn unlink ,
the
.Fn unlinkat
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 ENOTEMPTY
The
.Fa flag
parameter has the
.Dv AT_REMOVEDIR
bit set and the
.Fa path
argument names a directory that is not an empty directory,
or there are hard links to the directory other than dot or
a single entry in dot-dot.
.It Bq Er ENOTDIR
The
.Fa flag
parameter has the
.Dv AT_REMOVEDIR
bit set and
.Fa path
does not name a directory.
.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 SEE ALSO
.Xr close 2 ,
.Xr link 2 ,
.Xr rmdir 2 ,
.Xr symlink 7
.Sh STANDARDS
The
.Fn unlinkat
system call is expected to conform to POSIX.1-2008 .
.Sh HISTORY
An
.Fn unlink
function call appeared in 
.At v6 .
The
.Fn unlinkat
system call appeared in OS X 10.10
Commit	Line	Data
9bccf70c A	1	.\" $NetBSD: unlink.2,v 1.7 1995/02/27 12:39:13 cgd Exp $
	2	.\"
	3	.\" Copyright (c) 1980, 1991, 1993
	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	.\" @(#)unlink.2 8.1 (Berkeley) 6/4/93
	35	.\"
	36	.Dd June 4, 1993
	37	.Dt UNLINK 2
	38	.Os BSD 4
	39	.Sh NAME
fe8ab488 A	40	.Nm unlink ,
fe8ab488 A	41	.Nm unlinkat
9bccf70c A	42	.Nd remove directory entry
	43	.Sh SYNOPSIS
	44	.Fd #include <unistd.h>
	45	.Ft int
2d21ac55 A	46	.Fo unlink
	47	.Fa "const char *path"
	48	.Fc
fe8ab488 A	49	.Ft int
fe8ab488 A	50	.Fn unlinkat "int fd" "const char *path" "int flag"
9bccf70c A	51	.Sh DESCRIPTION
	52	The
	53	.Fn unlink
	54	function
	55	removes the link named by
	56	.Fa path
	57	from its directory and decrements the link count of the
	58	file which was referenced by the link.
	59	If that decrement reduces the link count of the file
	60	to zero,
	61	and no process has the file open, then
	62	all resources associated with the file are reclaimed.
	63	If one or more process have the file open when the last link is removed,
	64	the link is removed, but the removal of the file is delayed until
	65	all references to it have been closed.
fe8ab488 A	66	.Pp
	67	The
	68	.Fn unlinkat
	69	system call is equivalent to
	70	.Fn unlink
	71	or
	72	.Fn rmdir
	73	except in the case where
	74	.Fa path
	75	specifies a relative path.
	76	In this case the directory entry to be removed is determined
	77	relative to the directory associated with the file descriptor
	78	.Fa fd
	79	instead of the current working directory.
	80	.Pp
	81	The values for
	82	.Fa flag
	83	are constructed by a bitwise-inclusive OR of flags from the following list,
	84	defined in
	85	.In fcntl.h :
	86	.Bl -tag -width indent
	87	.It Dv AT_REMOVEDIR
	88	Remove the directory entry specified by
	89	.Fa fd
	90	and
	91	.Fa path
	92	as a directory, not a normal file.
	93	.El
	94	.Pp
	95	If
	96	.Fn unlinkat
	97	is passed the special value
	98	.Dv AT_FDCWD
	99	in the
	100	.Fa fd
	101	parameter, the current working directory is used and the behavior is
	102	identical to a call to
	103	.Fa unlink
	104	or
	105	.Fa rmdir
	106	respectively, depending on whether or not the
	107	.Dv AT_REMOVEDIR
	108	bit is set in flag.
9bccf70c A	109	.Sh RETURN VALUES
	110	Upon successful completion, a value of 0 is returned.
	111	Otherwise, a value of -1 is returned and
	112	.Va errno
	113	is set to indicate the error.
	114	.Sh ERRORS
	115	The
	116	.Fn unlink
2d21ac55	117	system call will fail if:
9bccf70c	118	.Bl -tag -width Er
2d21ac55	119	.\" ===========
9bccf70c A	120	.It Bq Er EACCES
9bccf70c A	121	Search permission is denied for a component of the path prefix.
2d21ac55	122	.\" ===========
9bccf70c A	123	.It Bq Er EACCES
	124	Write permission is denied on the directory containing the link
	125	to be removed.
2d21ac55 A	126	.\" ===========
	127	.It Bq Er EBUSY
	128	The entry to be unlinked is the mount point for a
	129	mounted file system.
	130	.\" ===========
	131	.It Bq Er EBUSY
	132	The file named by the
	133	.Fa path
	134	argument cannot be unlinked
	135	because it is being used by the system or by another process.
	136	.\" ===========
	137	.It Bq Er EFAULT
	138	.Fa Path
	139	points outside the process's allocated address space.
	140	.\" ===========
	141	.It Bq Er EIO
	142	An I/O error occurs while deleting the directory entry
	143	or deallocating the inode.
	144	.\" ===========
9bccf70c	145	.It Bq Er ELOOP
2d21ac55 A	146	Too many symbolic links are encountered in translating the pathname.
	147	This is taken to be indicative of a looping symbolic link.
	148	.\" ===========
	149	.It Bq Er ENAMETOOLONG
	150	A component of a pathname exceeds
	151	.Dv {NAME_MAX}
	152	characters, or an entire path name exceeds
	153	.Dv {PATH_MAX}
	154	characters (possibly as a result of expanding a symlink).
	155	.\" ===========
	156	.It Bq Er ENOENT
	157	The named file does not exist.
	158	.\" ===========
	159	.It Bq Er ENOTDIR
	160	A component of the path prefix is not a directory.
	161	.\" ===========
9bccf70c A	162	.It Bq Er EPERM
	163	The named file is a directory and the effective user ID
	164	of the process is not the super-user.
2d21ac55	165	.\" ===========
9bccf70c A	166	.It Bq Er EPERM
	167	The directory containing the file is marked sticky,
	168	and neither the containing directory nor the file to be removed
	169	are owned by the effective user ID.
2d21ac55	170	.\" ===========
9bccf70c A	171	.It Bq Er EROFS
9bccf70c A	172	The named file resides on a read-only file system.
9bccf70c	173	.El
fe8ab488 A	174	.Pp
	175	In addition to the errors returned by the
	176	.Fn unlink ,
	177	the
	178	.Fn unlinkat
	179	may fail if:
	180	.Bl -tag -width Er
	181	.It Bq Er EBADF
	182	The
	183	.Fa path
	184	argument does not specify an absolute path and the
	185	.Fa fd
	186	argument is neither
	187	.Dv AT_FDCWD
	188	nor a valid file descriptor open for searching.
	189	.It Bq Er ENOTEMPTY
	190	The
	191	.Fa flag
	192	parameter has the
	193	.Dv AT_REMOVEDIR
	194	bit set and the
	195	.Fa path
	196	argument names a directory that is not an empty directory,
	197	or there are hard links to the directory other than dot or
	198	a single entry in dot-dot.
	199	.It Bq Er ENOTDIR
	200	The
	201	.Fa flag
	202	parameter has the
	203	.Dv AT_REMOVEDIR
	204	bit set and
	205	.Fa path
	206	does not name a directory.
	207	.It Bq Er EINVAL
	208	The value of the
	209	.Fa flag
	210	argument is not valid.
	211	.It Bq Er ENOTDIR
	212	The
	213	.Fa path
	214	argument is not an absolute path and
	215	.Fa fd
	216	is neither
	217	.Dv AT_FDCWD
	218	nor a file descriptor associated with a directory.
	219	.El
9bccf70c A	220	.Sh SEE ALSO
	221	.Xr close 2 ,
	222	.Xr link 2 ,
2d21ac55	223	.Xr rmdir 2 ,
9bccf70c	224	.Xr symlink 7
fe8ab488 A	225	.Sh STANDARDS
	226	The
	227	.Fn unlinkat
	228	system call is expected to conform to POSIX.1-2008 .
9bccf70c A	229	.Sh HISTORY
	230	An
	231	.Fn unlink
	232	function call appeared in
	233	.At v6 .
fe8ab488 A	234	The
	235	.Fn unlinkat
	236	system call appeared in OS X 10.10