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@(#)access.2 8.2 (Berkeley) 4/1/94
$FreeBSD: head/lib/libc/sys/access.2 83797 2001-09-21 21:35:22Z rwatson $
.Dd April 1, 1994 .Dt ACCESS 2 .Os .Sh NAME .Nm access .Nd check access permissions of a file or pathname .Sh LIBRARY .Lb libc .Sh SYNOPSIS .Fd #include <unistd.h> .Ft int .Fn access "const char *path" "int mode" .Ft int .Fn eaccess "const char *path" "int mode" .Sh DESCRIPTION The .Fn access and .Fn eaccess functions check the accessibility of the file named by .Fa path for the access permissions indicated by .Fa mode . The value of .Fa mode is the bitwise inclusive OR of the access permissions to be checked
f ( 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 .
p For additional information, see the .Dq File Access Permission section of .Xr intro 2 .
p .Fn eaccess uses the effective user ID, group ID, and additional groups to authorize the request. .Fn access uses the real user ID 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.
p Even if a process's real or effective user 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; otherwise a 0 value is returned. .Sh ERRORS Access to the file is denied if: l -tag -width Er t Bq Er ENOTDIR A component of the path prefix is not a directory. t Bq Er ENAMETOOLONG A component of a pathname exceeded 255 characters, or an entire path name exceeded 1023 characters. t Bq Er ENOENT The named file does not exist. t Bq Er ELOOP Too many symbolic links were encountered in translating the pathname. t Bq Er EROFS Write access is requested for a file on a read-only file system. t Bq Er ETXTBSY Write access is requested for a pure procedure (shared text) file presently being executed. t 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. t Bq Er EFAULT .Fa Path points outside the process's allocated address space. t Bq Er EIO An I/O error occurred while reading from or writing to the file system. .El .Sh SEE ALSO .Xr chmod 2 , .Xr intro 2 , .Xr stat 2 .Sh STANDARDS The .Fn access function call is expected to conform to .St -p1003.1-90 . .Sh CAVEAT .Fn Access is a potential security hole due to race conditions and should never be used. Setuid and setgid applications should restore the effective uid or gid and perform actions directly rather than use .Fn access to simulate access checks for the real user of group id. .Fn Eaccess likewise may be subject to races if used inappropriately. .Sh HISTORY An .Fn access function call appeared in .At v7 .