This section specifies behaviors in which there is optional behavior in one of the standards on which this specification relies, and where this specification requires a specific behavior.
Note: This specification does not require the kernel to be Linux; the set of mandated options reflects current existing practice, but may be modified in future releases.
LSB conforming implementations shall support the following options defined within the ISO POSIX (2003):
function shall consume a file descriptor in the same
fashion as open(), and therefore may fail with
characters shall be changeable, as
described as optional behavior in the "General Terminal Interface"
section of the
ISO POSIX (2003).
The access() function
function shall fail with
EINVAL if the
amode argument contains bits other than
those set by the bitwise inclusive OR of
The link() function shall require access to the existing file in order to succeed, as described as optional behavior in the ISO POSIX (2003).
Calling unlink() on a directory shall fail. Calling link() specifying a directory as the first argument shall fail. See also unlink.
Note: Linux allows rename() on a directory without having write access, but this specification does not require this behavior.
LSB conforming systems shall enforce certain special additional restrictions above and beyond those required by ISO POSIX (2003).
Note: These additional restrictions are required in order to support the testing and certification programs associated with the LSB. In each case, these are values that defined macros must not have; conforming applications that use these values shall trigger a failure in the interface that is otherwise described as a "may fail".
The fcntl() function shall treat the "cmd" value -1 as invalid.
The whence value
shall be an invalid value for the
lseek(), fseek() and
-5 shall be an invalid signal number.
If the sigaddset() or
sigdelset() functions are passed an
invalid signal number, they shall return with EINVAL.
are only required to enforce this requirement for signal numbers which
are specified to be invalid by this specification (such as the
The mode value
-1 to the access()
function shall be treated as
A value of
-1 shall be an invalid "_PC_..." value for
A value of
-1 shall be an invalid "_SC..." value for
The nl_item value
shall be invalid for nl_langinfo().
-1 shall be an invalid "_CS_..." value for
"a" shall be an invalid mode
argument to popen().
The fcntl() function shall fail and set
EDEADLK if the
cmd argument is
and the lock is blocked by a lock from another process already blocked by the current process.
The opendir() function shall consume a file descriptor;
the readdir() function shall fail and set
to EBADF if the underlying file descriptor is closed.
The link() function shall not work across file systems, and
shall fail and set
errno to EXDEV
as described as optional behavior in ISO POSIX (2003).