organising files into folders

what happens if you redirect output to a file being used as input?
sort -n lengths.txt > lengths.txt

using >> to append output to a file

pipelines and understanding what text flows through each step of the pipeline

extensions don't mean anything -- .txt is just a convention

combining cut sort uniq wc

checking quality of data, removing damaged files

  * Most files’ names are something.extension. The extension isn’t required, and doesn’t guarantee anything, but is normally used to indicate the type of data in the file.
  * command >> [file] appends a command’s output to a file.
  * [first] | [second] is a pipeline: the output of the first command is used as the input to the second.
  * The best way to use the shell is to use pipes to combine simple single-purpose programs (filters).