behavior of test -nt and -ot when one of the files does not exist,
using the same behavior that is documented in ksh93.
@opindex -nt
@cindex newer-than file check
True if @var{file1} is newer (according to modification date) than
-@var{file2}.
+@var{file2}, or if @var{file1} exists and @var{file2} does not.
@item @var{file1} -ot @var{file2}
@opindex -ot
@cindex older-than file check
True if @var{file1} is older (according to modification date) than
-@var{file2}.
+@var{file2}, or if @var{file2} exists and @var{file1} does not.
@item @var{file1} -ef @var{file2}
@opindex -ef