If the filename begins with '<' or nothing, the file is opened for input.
If the filename begins with '>', the file is truncated and opened for
-output. If the filename begins with '>>', the file is opened for
-appending. You can put a '+' in front of the '>' or '<' to indicate that
+output, being created if necessary. If the filename begins with '>>',
+the file is opened for appending, again being created if necessary.
+You can put a '+' in front of the '>' or '<' to indicate that
you want both read and write access to the file; thus '+<' is almost
always preferred for read/write updates--the '+>' mode would clobber the
file first. You can't usually use either read-write mode for updating