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	1	.\" $NetBSD: readlink.2,v 1.7 1995/02/27 12:35:54 cgd Exp $
	2	.\"
	3	.\" Copyright (c) 1983, 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	.\" @(#)readlink.2 8.1 (Berkeley) 6/4/93
	35	.\"
	36	.Dd June 4, 1993
	37	.Dt READLINK 2
	38	.Os BSD 4.2
	39	.Sh NAME
	40	.Nm readlink ,
	41	.Nm readlinkat
	42	.Nd read value of a symbolic link
	43	.Sh SYNOPSIS
	44	.Fd #include <unistd.h>
	45	.Ft ssize_t
	46	.Fo readlink
	47	.Fa "const char *restrict path"
	48	.Fa "char *restrict buf"
	49	.Fa "size_t bufsize"
	50	.Fc
	51	.Ft ssize_t
	52	.Fo readlinkat
	53	.Fa "int fd" "const char restrict path" "char restrict buf" "size_t bufsize"
	54	.Fc
	55	.Sh DESCRIPTION
	56	.Fn Readlink
	57	places the contents of the symbolic link
	58	.Fa path
	59	in the buffer
	60	.Fa buf ,
	61	which has size
	62	.Fa bufsize .
	63	.Nm Readlink
	64	does not append a
	65	.Dv NUL
	66	character to
	67	.Fa buf .
	68	.Pp
	69	The
	70	.Fn readlinkat
	71	system call is equivalent to
	72	.Fn readlink
	73	except in the case where
	74	.Fa path
	75	specifies a relative path.
	76	In this case the symbolic link whose content is read relative to the
	77	directory associated with the file descriptor
	78	.Fa fd
	79	instead of the current working directory.
	80	If
	81	.Fn readlinkat
	82	is passed the special value
	83	.Dv AT_FDCWD
	84	in the
	85	.Fa fd
	86	parameter, the current working directory is used and the behavior is
	87	identical to a call to
	88	.Sh RETURN VALUES
	89	The call returns the count of characters placed in the buffer
	90	if it succeeds, or a -1 if an error occurs, placing the error
	91	code in the global variable
	92	.Va errno .
	93	.Sh ERRORS
	94	.Fn Readlink
	95	will fail if:
	96	.Bl -tag -width Er
	97	.\" ===========
	98	.It Bq Er EACCES
	99	Search permission is denied for a component of the path prefix.
	100	.\" ===========
	101	.It Bq Er EFAULT
	102	.Fa Buf
	103	extends outside the process's allocated address space.
	104	.\" ===========
	105	.It Bq Er EINVAL
	106	The named file is not a symbolic link.
	107	.\" ===========
	108	.It Bq Er EIO
	109	An I/O error occurred while reading from the file system.
	110	.\" ===========
	111	.It Bq Er ELOOP
	112	Too many symbolic links are encountered in translating the pathname.
	113	This is taken to be indicative of a looping symbolic link.
	114	.\" ===========
	115	.It Bq Er ENAMETOOLONG
	116	A component of a pathname exceeded
	117	.Dv {NAME_MAX}
	118	characters, or an entire path name
	119	(possibly expanded by a symbolic link) exceeded
	120	.Dv {PATH_MAX}
	121	characters.
	122	.\" ===========
	123	.It Bq Er ENOENT
	124	The named file does not exist.
	125	.\" ===========
	126	.It Bq Er ENOTDIR
	127	A component of the path prefix is not a directory.
	128	.El
	129	.Pp
	130	In addition to the errors returned by the
	131	.Fn readlink ,
	132	the
	133	.Fn readlinkat
	134	may fail if:
	135	.Bl -tag -width Er
	136	.It Bq Er EBADF
	137	The
	138	.Fa path
	139	argument does not specify an absolute path and the
	140	.Fa fd
	141	argument is neither
	142	.Dv AT_FDCWD
	143	nor a valid file descriptor open for searching.
	144	.It Bq Er ENOTDIR
	145	The
	146	.Fa path
	147	argument is not an absolute path and
	148	.Fa fd
	149	is neither
	150	.Dv AT_FDCWD
	151	nor a file descriptor associated with a directory.
	152	.El
	153	.Sh LEGACY SYNOPSIS
	154	.Fd #include <unistd.h>
	155	.Pp
	156	.Ft int
	157	.br
	158	.Fo readlink
	159	.Fa "const char *path"
	160	.Fa "char *buf"
	161	.Fa "int bufsize"
	162	.Fc ;
	163	.Pp
	164	The function type and the type of
	165	.Fa bufsize
	166	have changed.
	167	.Sh SEE ALSO
	168	.Xr lstat 2 ,
	169	.Xr stat 2 ,
	170	.Xr symlink 2 ,
	171	.Xr compat 5 ,
	172	.Xr symlink 7
	173	.Sh STANDARDS
	174	The
	175	.Fn readlinkat
	176	system call is expected to conform to POSIX.1-2008 .
	177	.Sh HISTORY
	178	The
	179	.Fn readlink
	180	function call appeared in
	181	.Bx 4.2 .
	182	The
	183	.Fn readlinkat
	184	system call appeared in OS X 10.10