coreutils: The sort command

 
 The ‘sort’ Command
 ==================
 
 Next we’ll look at the ‘sort’ command.  This is one of the most powerful
 commands on a Unix-style system; one that you will often find yourself
 using when setting up fancy data plumbing.
 
    The ‘sort’ command reads and sorts each file named on the command
 line.  It then merges the sorted data and writes it to standard output.
 It will read standard input if no files are given on the command line
 (thus making it into a filter).  The sort is based on the character
 collating sequence or based on user-supplied ordering criteria.