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

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 empty line?

Solution 1:

Many older tools misbehave if the last line of data in a text file is not terminated with a newline or carriage return / new line combination. They ignore that line as it is terminated with ^Z (eof) instead.

Solution 2:

If you try to concatenate two text files together, you will be much happier if the first one ends with a newline character.

Solution 3:

Apart from the fact that it is a nicer cursor position when you move to the end of a file in a text editor.

Having a newline at the end of the file provides a simple check that the file has not been truncated.

Solution 4:

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'
  ]

Solution 5:

The empty line in the end of file appears so that standard reading from the input stream will know when to terminate the read, usually returns EOF to indicate that you have reached the end. The majority of languages can handle the EOF marker. It is there for that reason from the old days, under DOS, the EOF marker was F6 key or Ctrl-Z, for *nix systems, it was Ctrl-D.

Most, if not all, will actually read right up to the EOF marker so that the runtime library's function of reading from input will know when to stop reading any further. When you open the stream for Append mode, it will wipe the EOF marker and write past it, until a close is explicitly called in which it will insert the EOF marker at that point.

Older tools were expecting a empty line followed by EOF marker. Nowadays, tools can handle the empty line and ignore it.