[ ]: ];eval "$(sed -n '/^/ {s|^|#!/usr/bin/env |p;q;}' $0; sed -n '/^/,/^/p' $0 | sed 's/^```.*//g'; echo exit $?);exit $?"

Executable Markdown

Instead of having a seperate file conatining the code inside your Markdown, you should be able to run it diretly. This also allows for some very nice literate programming.

How to use

Prepend your Markdown file with the following to make it executable. It needs to be run using your shell, sh README.md. To render properly on Github you need to replace all newlines with semicolons, to make one long line.

[ ]: ];eval "$(
  sed -n '/^```/ {s|^```|#!/usr/bin/env |p;q;}' $0
  sed -n '/^```/,/^```/p' $0 | sed 's/^```.*//g'
  echo exit \$?
);exit \$?"

How it's done

By prepending the file with a special link reference, that also happens to be valid shell script, it can parse itself and feed that to your shell.

The magical string is of the format: [ ]: ];eval "$(...);exit \$?"

The parsing is done using sed. To execute different languages correctly the resulting script needs to have a shebang, e.g. #!/usr/bin/env .... This is done by finding the first code fence and extracting its language. This is assumed to be usable in a #!/usr/bin/env ... context.

For the rest of the program all lines between code fences are extracted and concatanated using another sed script. However to allow just a part of a file to be executed you can use an alternative code fencing marker, e.g. tilde.

This is used above to hide the Markdown to ensure the example will work.

Example

To demonstrate this trick, this README contains the trick and the following will be executed if you run this file.

First code fence sets the executing enviroment:

echo $SHELL # /bin/bash
export SOMETHING="nice"

All code fences get concatenated before execution, effectivly sharing the same variable scope.

echo $SOMETHING # nice