Pipes and Filters
In one of its simplest forms, Pipes and Filters are available using a shell/console command line:
$ cat phone_numbers.txt | grep 303 | wc -l 3 $
Here a Linux command line is used to find how many contacts are in the fancy personal information manager,
phone_numbers.txt, who have Colorado-based phone numbers. Admittedly this is not a very reliable way to implement that use case, but it does demonstrate how Pipes and Filters work:
cat utility outputs the contents of
phone_numbers.txt to what is called the standard output stream. Normally this stream is connected to the console. But when the | symbol is used, the output is piped to the input of the next utility.
grep reads its input from the standard input stream, ...