run-md

#!/bin/bash

#
# Run code embeded into MarkDown documents
#

shopt -s expand_aliases

# Say something
alias say='echo 1>&2'

# Filter to extract code inside ``` blocks
function extract_code {
    local line
    local -i onblock=0

    local IFS=''
    while read -r line; do
        if [[ $line == '```'* ]]; then
            if (( onblock )); then
                onblock=0
            else
                onblock=1
            fi
            echo
        else
            if (( onblock )); then
                echo "$line"    # copy code inside block
            else
                echo    # replace other text with empty lines
            fi
        fi
    done
}

# Parse arguments
#   $1 is a MarkDown document (name.lang.md)
declare -r PROGRAM=${1?Expected program filename}
shift

declare -r CODE=/tmp/${PROGRAM%.md}
declare -r RUNNING=">>> Running $PROGRAM; temporary files left at /tmp:"

# Run extracted program
extract_code < "$PROGRAM" > "$CODE"

case "$CODE" in
    *.sh)
        say "$RUNNING ${PROGRAM%.md}"
        bash "$CODE" "$@"
        ;;
    *.py)
        say "$RUNNING ${PROGRAM%.md}"
        python "$CODE" "$@"
        ;;
    *.pl)
        say "$RUNNING ${PROGRAM%.md}"
        perl "$CODE" "$@"
        ;;
    *.c)
        say "$RUNNING ${PROGRAM%.md} and a.out"
        gcc "$CODE" -o /tmp/a.out && /tmp/a.out "$@"
        ;;
    *.cpp|*.cxx)
        say "$RUNNING ${PROGRAM%.md} and a.out"
        g++ "$CODE" -o /tmp/a.out && /tmp/a.out "$@"
        ;;
    *.java)
        say "$RUNNING ${PROGRAM%.md} and ${PROGRAM%.java.md}.class"
        javac -d /tmp "$CODE" && cd /tmp && java "${PROGRAM%.java.md}" "$@"
        ;;
    *)  # unsupported language: only extract code
        cat "$CODE"
        ;;
esac

exit

# vim:ai:et:sw=4:ts=4:syntax=sh