term% ls -F
term% pwd
term% cat index.txt
TR(1)                       General Commands Manual                      TR(1)

       tr - translate characters

       tr [ -cds ] [ string1 [ string2 ] ]

       Tr  copies  the standard input to the standard output with substitution
       or deletion of selected characters.  Input characters found in  string1
       are  mapped into the corresponding characters of string2.  When string2
       is short it is padded to the length of string1 by duplicating its  last
       character.  Any combination of the options -cds may be used: -c compleā€
       ments the set of characters in string1 with respect to the universe  of
       characters  whose ASCII codes are 01 through 0377 octal; -d deletes all
       input characters in string1; -s squeezes all strings of repeated output
       characters that are in string2 to single characters.

       In either string the notation a-b means a range of characters from a to
       b in increasing ASCII order.  The character `\' followed by 1, 2  or  3
       octal  digits  stands  for  the  character whose ASCII code is given by
       those digits.  A `\' followed by any other character  stands  for  that

       The  following  example  creates a list of all the words in `file1' one
       per line in `file2', where a word is taken to be a  maximal  string  of
       alphabetics.   The  second  string  is  quoted  to protect `\' from the
       Shell.  012 is the ASCII code for newline.

              tr -cs A-Za-z '\012' <file1 >file2

       ed(1), ascii(7)

       Won't handle ASCII NUL in string1 or string2; always deletes  NUL  from