mimetypes.el -- an elisp library for guessing mimetypes

Uses platform-dependent configurations for guessing the MIME type of a file extension.

Windows

The Windows registry is queried. HKEY_LOCAL_MACHINE\Software\Classes is checked for an entry for the extension. If the Content Type value under the extension's registry entry exists that is returned.

*nix

Guessing is done with a list of known mime.types files. See variable mimetypes-known-files. The first file found is searched for the desired extension. If one is not found, the remaining files are not checked for existence or searched.

MS-Dos / Cygwin

Determination of a mechanism, implementation and testing is still TODO. If needed please open a ticket.

extra-types argument

The optional argument extra-types can be used to specify a list of additional MIME types. Each element should be a list of strings. The first element being the MIME type, the remaining items being the mapped file extensions.

User .mime.types file

If a user-provided .mime.types file is found, the value provided there takes precendence over the platform-determined mechanism and extra-types list. If a MIME type isn't found for the extension in this file the platform-determined mechanism is used.

For Windows, this file is searched for under %USERPROFILE\.mime.types.

For all other platforms, $HOME/.mime.types is searched.

Examples

Guess mimetype for a file:

Guess a MIME type TARGET, which can be a buffer or string.

For buffers, an attempt will be made to get the MIME type with the file' command if it is available. If the buffer has a visited file the file name will specified as an argument to the file' command, otherwise the buffer's contents will be passed through standard input. If this check returns 'nil' or 'text/plain' a check is made for the MIME type by extension.

If TARGET is a string it is assumed to either be a file name or an extension. If a file by the name TARGET exists, a check is made with the `file' command. If this returns nil or 'text/plain' then check is made with the extension derived from TARGET or TARGET itself.

If EXTRA-TYPES is provided, it takes priority over other guessing mechanism. If the extension derived from the buffer or string is found in EXTRA-TYPES it will be returned.

(mimetypes-guess-mime "/path/to/foo.json")
-> "application/json"

(mimetypes-guess-mime (get-buffer "foo.json"))
-> "application/json"

To skip checking with the file process, set the variable mimetypes-bypass-file-proc to non-nil:

(let ((mimetypes-bypass-file-proc t))
  (mimetypes-guess-mime "jpg"))
-> "application/json"