.\" $NetBSD: access.2,v 1.7 1995/02/27 12:31:44 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. .\" .\" @(#)access.2 8.2 (Berkeley) 4/1/94 .\" .Dd April 1, 1994 .Dt ACCESS 2 .Os BSD 4 .Sh NAME .Nm access , .Nm faccessat .Nd check access permissions of a file or pathname .Sh SYNOPSIS .Fd #include .Ft int .Fo access .Fa "const char *path" .Fa "int amode" .Fc .Ft int .Fn faccessat "int fd" "const char *path" "int mode" "int flag" .Sh DESCRIPTION The .Fn access function checks the accessibility of the file named by .Fa path for the access permissions indicated by .Fa amode . The value of .Fa amode is the bitwise inclusive OR of the access permissions to be checked .Pf ( Dv R_OK for read permission, .Dv W_OK for write permission and .Dv X_OK for execute/search permission) or the existence test, .Dv F_OK . All components of the pathname .Fa path are checked for access permissions (including .Dv F_OK ) . .Pp The real user ID is used in place of the effective user ID and the real group access list (including the real group ID) are used in place of the effective ID for verifying permission. .Pp The .Fn faccessat system call is equivalent to .Fn access except in the case where .Fa path specifies a relative path. In this case the file whose accessibility is to be determined is located relative to the directory associated with the file descriptor .Fa fd instead of the current working directory. If .Fn faccessat 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 .Fn access . 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_EACCESS The checks for accessibility are performed using the effective user and group IDs instead of the real user and group ID as required in a call to .Fn access . .El .Pp Even if a process has appropriate privileges and indicates success for .Dv X_OK , the file may not actually have execute permission bits set. Likewise for .Dv R_OK and .Dv W_OK . .Sh RETURN VALUES If .Fa path cannot be found or if any of the desired access modes would not be granted, then a -1 value is returned and the global integer variable .Va errno is set to indicate the error. Otherwise, a 0 value is returned. .Sh ERRORS Access to the file is denied if: .Bl -tag -width Er .\" ========== .It Bq Er EACCES Permission bits of the file mode do not permit the requested access, or search permission is denied on a component of the path prefix. .Pp The owner of a file has permission checked with respect to the ``owner'' read, write, and execute mode bits, members of the file's group other than the owner have permission checked with respect to the ``group'' mode bits, and all others have permissions checked with respect to the ``other'' mode bits. .\" .\" ========== .It Bq Er EFAULT .Fa Path points outside the process's allocated address space. .It Bq Er EINVAL An invalid value was specified for .Ar amode . .\" ========== .It Bq Er EIO An I/O error occurred while reading from or writing to the file system. .\" ========== .It Bq Er ELOOP Too many symbolic links were encountered in translating the pathname. .\" ========== .It Bq Er ENAMETOOLONG A component of a pathname exceeded .Dv {NAME_MAX} characters, or an entire path name 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. .\" ========== .It Bq Er EROFS Write access is requested for a file on a read-only file system. .\" ========== .It Bq Er ETXTBSY Write access is requested for a pure procedure (shared text) file that is presently being executed. .El .Pp Also, the .Fn faccessat system call 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. .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 chmod 2 , .Xr stat 2 .Sh STANDARDS The .Fn access function conforms to .St -p1003.1-90 . The .Fn faccessat system call is expected to conform to POSIX.1-2008 . .Sh CAVEAT .Fn access is a potential security hole and should never be used.