reshape a data array

 rs reads the standard input, interpreting each line as a row of
 blank-separated entries in an array, transforms the array
 according to the options, and writes it on the standard output.
 Numerous options control input, reshaping and output processing;
 the simplest usage example is "ls -1 | rs", which outputs the
 same (on an 80-column terminal) as the modern "ls" with no "-1"
 argument.