1.\" $OpenBSD: access.2,v 1.4 1999/02/27 21:56:05 deraadt Exp $ 2.\" $NetBSD: access.2,v 1.7 1995/02/27 12:31:44 cgd Exp $ 3.\" 4.\" Copyright (c) 1980, 1991, 1993 5.\" The Regents of the University of California. All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 3. All advertising materials mentioning features or use of this software 16.\" must display the following acknowledgement: 17.\" This product includes software developed by the University of 18.\" California, Berkeley and its contributors. 19.\" 4. Neither the name of the University nor the names of its contributors 20.\" may be used to endorse or promote products derived from this software 21.\" without specific prior written permission. 22.\" 23.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33.\" SUCH DAMAGE. 34.\" 35.\" @(#)access.2 8.2 (Berkeley) 4/1/94 36.\" 37.Dd April 1, 1994 38.Dt ACCESS 2 39.Os BSD 4 40.Sh NAME 41.Nm access 42.Nd check access permissions of a file or pathname 43.Sh SYNOPSIS 44.Fd #include <unistd.h> 45.Ft int 46.Fn access "const char *path" "int mode" 47.Sh DESCRIPTION 48The 49.Fn access 50function checks the accessibility of the 51file named by 52.Fa path 53for the access permissions indicated by 54.Fa mode . 55The value of 56.Fa mode 57is the bitwise inclusive OR of the access permissions to be 58checked 59.Pf ( Dv R_OK 60for read permission, 61.Dv W_OK 62for write permission and 63.Dv X_OK 64for execute/search permission) or the existence test, 65.Dv F_OK . 66All components of the pathname 67.Fa path 68are checked for access permissions (including 69.Dv F_OK ) . 70.Pp 71The real user ID is used in place of the effective user ID 72and the real group access list 73(including the real group ID) are 74used in place of the effective ID for verifying permission. 75.Pp 76Even if a process has appropriate privileges and indicates success for 77.Dv X_OK , 78the file may not actually have execute permission bits set. 79Likewise for 80.Dv R_OK 81and 82.Dv W_OK . 83.Sh RETURN VALUES 84If 85.Fa path 86cannot be found or if any of the desired access modes would 87not be granted, then a -1 value is returned; otherwise 88a 0 value is returned. 89.Sh ERRORS 90Access to the file is denied if: 91.Bl -tag -width Er 92.It Bq Er ENOTDIR 93A component of the path prefix is not a directory. 94.It Bq Er ENAMETOOLONG 95A component of a pathname exceeded 96.Dv {NAME_MAX} 97characters, or an entire path name exceeded 98.Dv {PATH_MAX} 99characters. 100.It Bq Er ENOENT 101The named file does not exist. 102.It Bq Er ELOOP 103Too many symbolic links were encountered in translating the pathname. 104.It Bq Er EROFS 105Write access is requested for a file on a read-only file system. 106.It Bq Er ETXTBSY 107Write access is requested for a pure procedure (shared text) 108file presently being executed. 109.It Bq Er EACCES 110Permission bits of the file mode do not permit the requested 111access, or search permission is denied on a component of the 112path prefix. The owner of a file has permission checked with 113respect to the ``owner'' read, write, and execute mode bits, 114members of the file's group other than the owner have permission 115checked with respect to the ``group'' mode bits, and all 116others have permissions checked with respect to the ``other'' 117mode bits. 118.It Bq Er EFAULT 119.Fa path 120points outside the process's allocated address space. 121.It Bq Er EIO 122An I/O error occurred while reading from or writing to the file system. 123.It Bq Er EINVAL 124An invalid value was specified for 125.Ar mode . 126.El 127.Sh SEE ALSO 128.Xr chmod 2 , 129.Xr stat 2 130.Sh STANDARDS 131The 132.Fn access 133function conforms to 134.St -p1003.1-90 . 135.Sh CAVEAT 136.Fn access 137is a potential security hole and 138should never be used. 139