It uses the output of the command as an input source. $(ls) would have done the same thing... I like to think of it as performing the operation on a current set.
It doesn't look familiar because its a specific parallel command option, not a general bash option.
Another silly example of a clock-counter ... the -k flag says keep the order (so things don't happen out of order). Perform an echo operation on three sets.
It uses the output of the command as an input source. $(ls) would have done the same thing... I like to think of it as performing the operation on a current set.
It doesn't look familiar because its a specific parallel command option, not a general bash option.
Another silly example of a clock-counter ... the -k flag says keep the order (so things don't happen out of order). Perform an echo operation on three sets.