tr
Unix-like operating system command
tr is a command in Unix, Plan 9, Inferno, and Unix-like operating systems. It is an abbreviation of translate or transliterate, indicating its operation of replacing or removing specific characters in its input data set. Wikipedia
Example: tr A-Z a-z lower
Developer(s): Various open-source and commercial developers
Original author(s): Douglas McIlroy; (AT&T Bell Laboratories)
Written in: C