On MS-DOS and Microsoft Windows, Emacs guesses the appropriate end-of-line conversion for a file by looking at the file's name. This feature classifies files as text files and binary files. By “binary file” we mean a file of literal byte values that are not necessarily meant to be characters; Emacs does no end-of-line conversion and no character code conversion for them. On the other hand, the bytes in a text file are intended to represent characters; when you create a new file whose name implies that it is a text file, Emacs uses DOS end-of-line conversion.
This variable, automatically buffer-local in each buffer, records the file type of the buffer's visited file. When a buffer does not specify a coding system with
buffer-file-coding-system, this variable is used to determine which coding system to use when writing the contents of the buffer. It should be
tfor binary. If it is
t, the coding system is
Normally this variable is set by visiting a file; it is set to
nilif the file was visited without any actual conversion.
Its default value is used to decide how to handle files for which
file-name-buffer-file-type-alistsays nothing about the type: If the default value is non-
nil, then these files are treated as binary: the coding system
no-conversionis used. Otherwise, nothing special is done for them—the coding system is deduced solely from the file contents, in the usual Emacs fashion.
This variable holds an alist for recognizing text and binary files. Each element has the form (regexp . type), where regexp is matched against the file name, and type may be
tfor binary, or a function to call to compute which. If it is a function, then it is called with a single argument (the file name) and should return
When running on MS-DOS or MS-Windows, Emacs checks this alist to decide which coding system to use when reading a file. For a text file,
undecided-dosis used. For a binary file,
If no element in this alist matches a given file name, then the default value of
buffer-file-typesays how to treat the file.