The tr utility copies the standard input to the standard output with substitution or deletion of selected characters. The arguments string1 and string2 are considered sets of characters. Any input character found in string1 is mapped into the character in the corresponding position within string2. When string2 is short, it is padded to the length of string1 by duplicating its last character.
In either string the notation:
denotes 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. As with the shell, the escape character \,
followed by any other character, escapes any special meaning for that character.