When writing executable scripts, and declarative configuration files that use a common language (eg. Python), I often find it undesirable to add an extension to the file name. Many syntax-highlighting text editor (eg. Geany) are subsequently unable to automatically determine the filetype.
Is there any standard method for indicating to editors the type of source in the file?
Typically the shebang line is used as a fall-back.
For example, a Ruby script without an extension would begin with:
#!/usr/bin/env ruby
Vim has a concept called a modeline. A modeline is a specially formatted line either withinin the first or last 5 lines of the textfile, which allows you to :setlocal local variables. For example, for C:
/* vi: set filetype=c fileencoding=UTF-8 shiftwidth=4 tabstop=4 expandtab */
or Ruby:
# vi: set filetype=ruby fileencoding=UTF-8 shiftwidth=2 tabstop=2 expandtab
Some more documentation.
Emacs has a similar concept, called File Variables.
File Variables are either specified at the beginning of the file (in the first line, or if there is a shebang line, then in the second) in this form:
/* *-* mode: cc c-basic-offset: 4; tab-width: 4; indent-tabs-mode: nil *-* */
or at the end:
# Local Variables:
# mode: ruby
# coding: utf-8
# c-basic-offset: 2
# tab-width: 2
# indent-tabs-mode: nil
# End:
jEdit calls this buffer-local properties. The have to sit within the first or last 10 lines and look like this:
# :mode=ruby:indentSize=2:tabSize=2:noTabs=true:
jEdit also uses the shebang line as a fallback for mode detection.
There is a plugin called Komode (pun intended) which adds modeline support to Komodo Edit:
# komode: le=unix language=ruby codepage=utf8 tab=2 notabs indent=2
It also understands a limited subset of Vim modelines.
A lot of other editors also have either their own variants of this, or support one of the above (usually Vim).
Both Ruby 1.9 and Python require that the encoding for non-ASCII source files be explicitly specified. Fortunately, they do this in a way that is compatible with both Emacs and Vim modelines. (Basically, they look for the string coding followed by a non-word character followed by whitespace followed by a valid encoding name. Both Vim's fileencoding= and Emacs' coding: satisfy these requirements.)
Here is a simple modeline generator, which generates modelines for Vim, Emacs and jEdit.
This works for many editors if you're using non-standard shebangs:
#!/usr/bin/env python3
# filetype=python
