View source for Piping and redirecting output from one command or file to another

Piping entails sending standard output to the standard input of a linux command. 
Pipes are the primary power of using the command line. They can be used with sed, awk, perl, and python
amongst other tools to produce very specific behavior.   To pipe the output to a new command place a '|'
character between them.

Examples 

=== command line pipe ===

 wc -l * | sort -rn

=== pipes in for loops ===

  for f in `ls -al | awk '{print$9}' | sort`; 
  do 
     echo $f; 
     cp $f $f.bak; 
  done

=== named pipes ===

Another way of piping is to set up a pipe that can persist outside of a specific command line.
This can also be used to monitor calculations that are in progress.  

For example (from wikipedia), one can create a pipe and set up gzip to compress things piped to it:
 mkfifo my_pipe
 gzip -9 -c < my_pipe > out.gz
 rm my_pipe
In a separate process shell, independently, one could send the data to be compressed:
 cat file > my_pipe