The operation sorts the given data frame <data> according to the keys in the frame <keydata>. If a result data is the same as <data>, then the frame <data> is replaced with the sorted data, otherwise a new data is created.
Example (ex3.4): Here are some sortings for data frames.
... # ascending rate, replacing source with result NDA> select key1 -f boston.rate NDA> sort -k key1 -d boston -dout boston ... # two fields as keys with priorities: 1.dis 2.rm NDA> select key2 -f boston.dis boston.rm NDA> sort -k key2 -d boston -dout boston2 ...