Exacutable files
Content files may be executables. If a file is executable its content from stdout will be used instead of actual file content. The output form the executable is treated identically to a regular content file, so it may specify headers and non-header content will be passed to the appropriate markup engine.
Example shell script
#!/bin/bash
#Print any desired headers, e.g.
echo "Title: This will be the page title"
echo "" # Start content
echo "$(hostname)"