This allows a number of small, special-purpose programs to be linked together to perform a more complicated task. Filters are designed to be fairly small, smimple, special-purpose, and above all modular . This allows them to be used in a number of different situations without having to be modified. No other program need be concerned with sorting data because sort does it so well. Other programs needing sorted data would simple create a pipe containing sort, and read from it.
Data flows from left to right through the command line, passing through each filter in order.
There can be any number of filters in a pipe, so long as all obey this rule.