Getting ready

The tr command accepts input through stdin (standard input) and cannot accept input through command-line arguments. It has this invocation format:

tr [options] set1 set2

Input characters from stdin are mapped from the first character in set1 to the first character in set2, and so on and the output is written to stdout (standard output). set1 and set2 are character classes or a set of characters. If the length of sets is unequal, set2 is extended to the length of set1 by repeating the last character; otherwise if the length of set2 is greater than that of set1, all the characters exceeding the length of set1 are ignored from set2.