tr(1) - translate or delete characters
tr [OPTION]... SET1 [SET2]

Translate, squeeze, and/or delete characters from standard input, writing to standard output.
-c, -C, --complement
       use the complement of SET1
-d, --delete
       delete characters in SET1, do not translate
-s, --squeeze-repeats
       replace  each  input  sequence  of  a  repeated  character  that  is  listed in SET1 with a single
       occurrence of that character
-t, --truncate-set1
       first truncate SET1 to length of SET2
--help display this help and exit
       output version information and exit
SETs are specified as strings of characters.  Most represent themselves.  Interpreted sequences are:

\NNN   character with octal value NNN (1 to 3 octal digits)

\\     backslash

\a     audible BEL

\b     backspace

\f     form feed

\n     new line

\r     return

\t     horizontal tab

\v     vertical tab

       all characters from CHAR1 to CHAR2 in ascending order

       in SET2, copies of CHAR until length of SET1

       REPEAT copies of CHAR, REPEAT octal if starting with 0

       all letters and digits

       all letters

       all horizontal whitespace

       all control characters

       all digits

       all printable characters, not including space

       all lower case letters

       all printable characters, including space

       all punctuation characters

       all horizontal or vertical whitespace

       all upper case letters

       all hexadecimal digits

       all characters which are equivalent to CHAR