mustache.sh

There's (as of this writing) only one call to a non-builtin which is probably enough to claim this is fast enough for most uses.

mustache.sh requires GNU sed(1).

Installation

make && sudo make install

From the command-line:

FOO="foo" BAR="bar" mustache.sh <"tests/test.mustache"

As a library:

. "lib/mustache.sh"
FOO="foo" BAR="bar"
mustache <"tests/test.mustache"

mustache.sh accepts input data via the environment, not via YAML frontmatter. This makes sense for shell programmers but may render this Mustache implementation unsuitable for other use.
mustache.sh does not descend into a new scope within {{#tag}} or {{^tag}} sections. This again makes sense when being driven by environment variables.
mustache.sh doesn't support the --compile or --tokens command-line options and does not accept input file(s) as arguments.
mustache.sh doesn't care about escaping output as HTML.
mustache.sh will execute tag names surrounded by backticks as shell commands.
mustache.sh doesn't support list sections in the traditional sense: it requires the section tag be a shell command and processes the section once for each line on standard output with the line available in _M_LINE.

Lambdas. What is this I don't even.
Partials. This is related to supporting shell commands as variables.
Set delimeter. This would be very hard to support in general because of the pervasive assumption that tag delimeters are two characters long.

Variable tags.
Section tags.
Inverted section tags.
Comment tags.
Nested sections. Recursion, motherfucker. Do you speak it?
List sections. The section tag must be a shell command. The section is processed once for each line on standard output with the line available in _M_LINE.

mustache.sh is BSD-licensed.