Update 04-pipefilter.md

Rearranged the Objectives of the episode to match the current discussion, in order of appearance.

Need some edits more to emphasize the UNIX filters 'philosophy', i.e. 'programs that do one thing, and do it well'.

episodes/04-pipefilter.md

@@ -6,16 +6,17 @@ exercises: 10
 
 ::::::::::::::::::::::::::::::::::::::: objectives
 
+- Explain the advantage of linking commands with pipes and filters.
+- Combine commands in more than one stages to get new output
 - Redirect a command's output to a file.
-- Construct command pipelines with two or more stages.
 - Explain what usually happens if a program or pipeline isn't given any input to process.
-- Explain the advantage of linking commands with pipes and filters.
 
 ::::::::::::::::::::::::::::::::::::::::::::::::::
 
 :::::::::::::::::::::::::::::::::::::::: questions
 
-- How can I combine existing commands to do new things?
+- How can I produce various forms of the output of existing commands? How to show only part of the output? ( -> command line switches and pipes)
+- How can I combine existing commands to do new things? ( -> pipes)
 
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