See the "Base Definitions" Volume of SUS. In SUS4, it's Chapter
3 "Definitions",
3.395 Text File
A file that contains characters organized into zero or more
lines. The lines do not contain NUL characters and none
can exceed {LINE_MAX} bytes in length, including the
<newline> character. Although POSIX.1-2008 does not
distinguish between text files and binary files (see the
ISO C standard), many utilities only produce predictable
or meaningful output when operating on text files. The
standard utilities that have such restrictions always
specify "text files" in their STDIN or INPUT FILES sections.
Martin
