NAME

access − determine accessibility of file

SYNOPSIS

#define R_OK4 /∗ test for read permission ∗/
#define W_OK2 /∗ test for write permission ∗/
#define X_OK1 /∗ test for execute (search) permission ∗/
#define F_OK0 /∗ test for presence of file ∗/
 accesible = access(path, mode)
int accessible;
char ∗path;
int mode;

DESCRIPTION

Access checks the given file path for accessibility according to mode, which is an inclusive or of the bits R_OK, W_OK and X_OK. Specifying mode as F_OK (that is, 0) tests whether the directories leading to the file can be searched and the file exists.

The real user ID and the group access list (including the real group ID) are used in verifying permission, so this call is useful to set-UID programs. 

Notice that it is only access bits that are checked.  A directory may be announced as writable by access, but an attempt to open it for writing will fail (although files may be created there); a file may look executable, but exec will fail unless it is in proper format. 

RETURN VALUE

If 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. 

ERRORS

Access to the file is denied if one or more of the following are true:

[ENOTDIR] A component of the path prefix is not a directory. 

[ENOENT] The argument path name was too long. 

[ENOENT] The named file does not exist. 

[EPERM] The path argument contained a byte with the high-order bit set and the request made against the file was something other than an attempt to delete the file. 

[ELOOP] Too many symbolic links were encountered in translating the pathname. 

[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 being executed. 

[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 valid address space. 

SEE ALSO

chmod(2), stat(2)

Sun System Release 0.3  —  25 April 1983