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Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)access.2 8.2 (Berkeley) 4/1/94 33.\" $FreeBSD: src/lib/libc/sys/access.2,v 1.7.2.5 2002/10/12 22:02:53 rwatson Exp $ 34.\" $DragonFly: src/lib/libc/sys/access.2,v 1.2 2003/06/17 04:26:47 dillon Exp $ 35.\" 36.Dd April 1, 1994 37.Dt ACCESS 2 38.Os 39.Sh NAME 40.Nm access 41.Nd check access permissions of a file or pathname 42.Sh LIBRARY 43.Lb libc 44.Sh SYNOPSIS 45.In unistd.h 46.Ft int 47.Fn access "const char *path" "int mode" 48.Sh DESCRIPTION 49The 50.Fn access 51function checks the accessibility of the 52file named by 53.Fa path 54for the access permissions indicated by 55.Fa mode . 56The value of 57.Fa mode 58is the bitwise inclusive OR of the access permissions to be 59checked 60.Pf ( Dv R_OK 61for read permission, 62.Dv W_OK 63for write permission and 64.Dv X_OK 65for execute/search permission) or the existence test, 66.Dv F_OK . 67All components of the pathname 68.Fa path 69are checked for access permissions (including 70.Dv F_OK ) . 71.Pp 72The real user ID is used in place of the effective user ID 73and the real group access list 74(including the real group ID) are 75used in place of the effective ID for verifying permission. 76.Pp 77Even if a process has appropriate privileges and indicates success for 78.Dv X_OK , 79the file may not actually have execute permission bits set. 80Likewise for 81.Dv R_OK 82and 83.Dv W_OK . 84.Sh RETURN VALUES 85If 86.Fa path 87cannot be found or if any of the desired access modes would 88not be granted, then a -1 value is returned; otherwise 89a 0 value is returned. 90.Sh ERRORS 91Access to the file is denied if: 92.Bl -tag -width Er 93.It Bq Er ENOTDIR 94A component of the path prefix is not a directory. 95.It Bq Er ENAMETOOLONG 96A component of a pathname exceeded 255 characters, 97or an entire path name exceeded 1023 characters. 98.It Bq Er ENOENT 99The named file does not exist. 100.It Bq Er ELOOP 101Too many symbolic links were encountered in translating the pathname. 102.It Bq Er EROFS 103Write access is requested for a file on a read-only file system. 104.It Bq Er ETXTBSY 105Write access is requested for a pure procedure (shared text) 106file presently being executed. 107.It Bq Er EACCES 108Permission bits of the file mode do not permit the requested 109access, or search permission is denied on a component of the 110path prefix. The owner of a file has permission checked with 111respect to the ``owner'' read, write, and execute mode bits, 112members of the file's group other than the owner have permission 113checked with respect to the ``group'' mode bits, and all 114others have permissions checked with respect to the ``other'' 115mode bits. 116.It Bq Er EFAULT 117.Fa Path 118points outside the process's allocated address space. 119.It Bq Er EIO 120An I/O error occurred while reading from or writing to the file system. 121.El 122.Sh SEE ALSO 123.Xr chmod 2 , 124.Xr stat 2 125.Sh STANDARDS 126The 127.Fn access 128function call is expected to conform to 129.St -p1003.1-90 . 130.Sh CAVEAT 131.Fn Access 132is a potential security hole due to race conditions and 133should never be used. 134Setuid and setgid applications should restore the effective uid or gid 135and perform actions directly rather than use 136.Fn access 137to simulate access checks for the real user of group id. 138.Sh HISTORY 139An 140.Fn access 141function call appeared in 142.At v7 . 143