Why is it recommended to have empty line in the end of a source file?

Question

Some code style tools recommend this and I remember seeing some unix command line tools warning about missing empty line.

What is the reasoning for having an extra e

Answer 1

Some languages define their input file in terms of input lines, where each input line is a series of characters terminated by a carriage return. If their grammar is so defined, then the last valid line of the file must be terminated by a carriage return too.

Answer 2

An argument can also be made for cleaner diffs if you append to the file following the same reasoning as Why are trailing commas allowed in a list?

The following is copied (and trimmed a bit) from the linked resource:

Changing:

s = [
  'manny',
  'jack',
]

to:

s = [
  'manny',
  'jack',
  'roger',
]

involves only a one-line change in the diff:

  s = [
    'manny',
    'jack',
+   'roger',
  ]

This beats the more confusing multi-line diff when the trailing comma was omitted:

  s = [
    'manny',
-   'jack'
+   'jack',
+   'roger'
  ]