Goals for this Hour

In this hour, you learn

• The secrets of file redirection

• How to count words and lines using wc

• How to remove extraneous lines using uniq

• How to sort information in a file using sort

This hour begins by focusing on one aspect of constructing powerful custom commands in UNIX by using file redirection. The introduction of some filters—programs that are intended to be used as part of command pipes—follow. Next you learn another aspect of creating your own UNIX commands using pipelines.