1. The prompt and the file system

Every programmer starts here. In this lesson you write a complete program, run it, and change it until it does what you want.

Pipes and redirectionbash

# The ten most common words in a book
tr -cs 'A-Za-z' '\n' < book.txt | tr 'A-Z' 'a-z' \
  | sort | uniq -c | sort -rn | head -10

Your turn

Change the program so it greets you by name, then run it in the playground. The checks turn green when the output matches.