cheat sheets.

tr:
  Translates characters, but, generally, is used to substitute or delete
characters from the content of standard input.

  Forms:
  
    tr [-Ccsu] string1 string2
    tr [-Ccu] -d string1
    tr [-Ccu] -s string1
    tr [-Ccu] -ds string1 string2


  Options:

    -C      # Complement characters in string1. Everything except for the listed
    characters.
    $ echo "0123456789" | tr -C 13579 "[:number:]" " "
    
    -c     # Same as -C but complement the set of values in string1.

    -d     # Delete characters in string1 from the input.

    -s     # Squeeze multiple occurrences of the characters listed in the last
    operand
            (either string1 or string2) in the input into a single instance of
            the character.
            This occurs after all deletion and translation is completed.

    -u      # Guarantee that any output is unbuffered.


  Escape Chars:

    \char   # A backslash followed by special characters escapes it to have
    special meaning.

    \a      # Alert
    \b      # Backspace
    \f      # Form Feed
    \n      # Newline
    \r      # Carriage Return
    \t      # Tab>
    \v      # Vertical Tab

 

  Examples:
  
    tr -cs "[:alpha:]" "\n" < file1
    $ echo "Round\t the\brugged" | tr -cs "[:alpha:]" "\n"
    Round
    the
    rugged
    
      # Create a list of the words in file1, one per line, where a word is
      #  taken to be a maximal string of letters.


    tr "[:lower:]" "[:upper:]" < file1
    
      # Translate the contents of file1 to upper-case.


    tr a-z A-Z
    $ echo "hello world" | tr a-z A-Z
    HELLO WORLD
    
      # A less locale-portable, but very common way to translate lowercase to
      upper case.


    tr -cd "[:print:]" < file1
    
      # Strip out non-printable characters from file1.


    tr "[=e=]" "e"
    
      # Remove diacritical marks from all accented variants of the letter `e'