access(2) BSD System Calls Manual access(2)

NAME

 access -- check access permissions of a file or pathname

SYNOPSIS

 #include <unistd.h>
 int
 access(const char *path, int amode);

DESCRIPTION

 The access() function checks the accessibility of the file named by path
 for the access permissions indicated by amode. The value of amode is the
 bitwise inclusive OR of the access permissions to be checked (R_OK for
 read permission, W_OK for write permission and X_OK for execute/search
 permission) or the existence test, F_OK. All components of the pathname
 path are checked for access permissions (including F_OK).
 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.
 Even if a process has appropriate privileges and indicates success for
 X_OK, the file may not actually have execute permission bits set. Like-
 wise for R_OK and W_OK.

RETURN VALUES

 If 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
 errno is set to indicate the error. Otherwise, a 0 value is returned.

ERRORS

 Access to the file is denied if:
 [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.
 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.
 [EFAULT] Path points outside the process's allocated address
 space.
 [EINVAL] An invalid value was specified for amode.
 [EIO] An I/O error occurred while reading from or writing to
 the file system.
 [ELOOP] Too many symbolic links were encountered in translat-
 ing the pathname.
 [ENAMETOOLONG] A component of a pathname exceeded {NAME_MAX} charac-
 ters, or an entire path name exceeded {PATH_MAX} char-
 acters.
 [ENOENT] The named file does not exist.
 [ENOTDIR] A component of the path prefix is not a directory.
 [EROFS] Write access is requested for a file on a read-only
 file system.
 [ETXTBSY] Write access is requested for a pure procedure (shared
 text) file that is presently being executed.

SEE ALSO

 chmod(2) , stat(2) 

STANDARDS

 The access() function conforms to ISO/IEC 9945-1:1990 (``POSIX.1'').

CAVEAT

 Access() is a potential security hole and should never be used.
4th Berkeley Distribution April 1, 1994 4th Berkeley Distribution