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

.\"	$NetBSD: readlink.2,v 1.7 1995/02/27 12:35:54 cgd Exp $
.\"
.\" Copyright (c) 1983, 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.
.\"
.\"     @(#)readlink.2	8.1 (Berkeley) 6/4/93
.\"
.Dd June 4, 1993
.Dt READLINK 2
.Os BSD 4.2
.Sh NAME
.Nm readlink
.Nd read value of a symbolic link
.Sh SYNOPSIS
.Fd #include <unistd.h>
.Ft  ssize_t
.Fo readlink
.Fa "const char *restrict path"
.Fa "char *restrict buf"
.Fa "size_t bufsize"
.Fc
.Sh DESCRIPTION
.Fn Readlink
places the contents of the symbolic link
.Fa path
in the buffer
.Fa buf ,
which has size
.Fa bufsize .
.Nm Readlink
does not append a
.Dv NUL
character to
.Fa buf .
.Sh RETURN VALUES
The call returns the count of characters placed in the buffer
if it succeeds, or a -1 if an error occurs, placing the error
code in the global variable
.Va errno .
.Sh ERRORS
.Fn Readlink
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 Buf
extends outside the process's allocated address space.
.\" ===========
.It Bq Er EINVAL
The named file is not a symbolic link.
.\" ===========
.It Bq Er EIO
An I/O error occurred while reading from 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 exceeded 
.Dv {NAME_MAX}
characters, or an entire path name
(possibly expanded by a symbolic link) exceeded 
.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
.Sh LEGACY SYNOPSIS
.Fd #include <unistd.h>
.Pp
.Ft int
.br
.Fo readlink
.Fa "const char *path"
.Fa "char *buf"
.Fa "int bufsize"
.Fc ;
.Pp
The function type and the type of
.Fa bufsize
have changed.
.Sh SEE ALSO
.Xr lstat 2 ,
.Xr stat 2 ,
.Xr symlink 2 ,
.Xr compat 5 ,
.Xr symlink 7
.Sh HISTORY
The
.Fn readlink
function call appeared in
.Bx 4.2 .
Commit	Line	Data
9bccf70c A	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	.Nd read value of a symbolic link
	42	.Sh SYNOPSIS
	43	.Fd #include <unistd.h>
2d21ac55 A	44	.Ft ssize_t
	45	.Fo readlink
	46	.Fa "const char *restrict path"
	47	.Fa "char *restrict buf"
	48	.Fa "size_t bufsize"
	49	.Fc
9bccf70c A	50	.Sh DESCRIPTION
	51	.Fn Readlink
	52	places the contents of the symbolic link
	53	.Fa path
	54	in the buffer
	55	.Fa buf ,
	56	which has size
2d21ac55	57	.Fa bufsize .
9bccf70c A	58	.Nm Readlink
	59	does not append a
	60	.Dv NUL
	61	character to
	62	.Fa buf .
	63	.Sh RETURN VALUES
	64	The call returns the count of characters placed in the buffer
	65	if it succeeds, or a -1 if an error occurs, placing the error
	66	code in the global variable
	67	.Va errno .
	68	.Sh ERRORS
	69	.Fn Readlink
	70	will fail if:
	71	.Bl -tag -width Er
2d21ac55 A	72	.\" ===========
	73	.It Bq Er EACCES
	74	Search permission is denied for a component of the path prefix.
	75	.\" ===========
	76	.It Bq Er EFAULT
	77	.Fa Buf
	78	extends outside the process's allocated address space.
	79	.\" ===========
	80	.It Bq Er EINVAL
	81	The named file is not a symbolic link.
	82	.\" ===========
	83	.It Bq Er EIO
	84	An I/O error occurred while reading from the file system.
	85	.\" ===========
	86	.It Bq Er ELOOP
	87	Too many symbolic links are encountered in translating the pathname.
	88	This is taken to be indicative of a looping symbolic link.
	89	.\" ===========
9bccf70c A	90	.It Bq Er ENAMETOOLONG
	91	A component of a pathname exceeded
	92	.Dv {NAME_MAX}
2d21ac55 A	93	characters, or an entire path name
2d21ac55 A	94	(possibly expanded by a symbolic link) exceeded
9bccf70c A	95	.Dv {PATH_MAX}
9bccf70c A	96	characters.
2d21ac55	97	.\" ===========
9bccf70c A	98	.It Bq Er ENOENT
9bccf70c A	99	The named file does not exist.
2d21ac55 A	100	.\" ===========
	101	.It Bq Er ENOTDIR
	102	A component of the path prefix is not a directory.
9bccf70c	103	.El
2d21ac55 A	104	.Sh LEGACY SYNOPSIS
	105	.Fd #include <unistd.h>
	106	.Pp
	107	.Ft int
	108	.br
	109	.Fo readlink
	110	.Fa "const char *path"
	111	.Fa "char *buf"
	112	.Fa "int bufsize"
	113	.Fc ;
	114	.Pp
	115	The function type and the type of
	116	.Fa bufsize
	117	have changed.
9bccf70c	118	.Sh SEE ALSO
9bccf70c	119	.Xr lstat 2 ,
2d21ac55 A	120	.Xr stat 2 ,
	121	.Xr symlink 2 ,
	122	.Xr compat 5 ,
	123	.Xr symlink 7
9bccf70c A	124	.Sh HISTORY
	125	The
	126	.Fn readlink
	127	function call appeared in
	128	.Bx 4.2 .