Command Pipelines As mentioned earlier, the power of UNIX lies in its modularity. Each command does one thing well. UNIX allows you to combine several of these single-purpose commands into a command pipeline . If there are more files in the directory than can be displayed on a single screen, this command lets you page through them at your leisure.
Pipes allow the output of one command to become the input to another.
UNIX uses the terms standard output and standard input to refer to the two ends of a pipe. The shell is responsible for making sure the beginning and end of a pipeline are connected properly to a meaningful source and destination. Here's another, more complicated, example of a pipeline.