POSIX の定義では『テキストファイル』はファイル末尾に改行が必要

3.392 Text File

A file that contains characters organized into one or more lines. https://pubs.opengroup.org/onlinepubs/000095399/basedefs/xbd_chap03.html#tag_03_392

3.205 Line

A sequence of zero or more non- s plus a terminating . https://pubs.opengroup.org/onlinepubs/000095399/basedefs/xbd_chap03.html#tag_03_205