tr
From NetBSD Wiki
The tr(1) command translates a list of characters to another list of characters in a file.
Example:
$ echo abcdefabcdef | tr adf xyz xbcyezxbcyez
Characters are positionally translated from the first list to the second. In the example, the character a is translated to an x, d is translated to y and f to z.
Other uses
You can also use tr to delete characters from its input, with the -d switch and only one list of characters:
$ echo abcdefabcdef | tr -d adf bcebce
One common usage is to delete carriaage-return (ASCII 13) from files created in DOS or Windows systems:
$ tr -d '\r' <dos-file.txt >unix-file.txt
