"Watch and Run" shell script

17 February 2019

I am using Python a lot lately for machine learning. To experiment a lot and quickly, I am using a simple shell-script that automatically runs my Python script whenever I change it. This is not only useful for Python but for any task that should be triggered based on a changed file.

war() {
    war_do() {
        clear;
        the_time=$(date +%H:%M:%S)
        start=$(date +%s.%N)
        # Run the command that was provided as argument
        eval $@;
        rc=$?
        end=$(date +%s.%N)
        diff=$(echo "${end} - ${start}" | bc)
        if [ $rc -eq 0 ]; then
            echo ""
            echo -e "\e[2m[${the_time}]\e[0m \e[1;32m** Successful **\e[0m \e[2m(time: ${diff} seconds)\e[0m"
        else
            echo ""
            echo -e "\e[2m[${the_time}]\e[0m \e[1;31m** Failed **\e[0m"
        fi
        sleep 1;
    }
    war_do $@
    while inotifywait -qq .; do
        war_do $@
    done
}

You have to make sure that inotifywait is available on your system. Assume you source the script in your .bashrc, you can now run below command to contiously run your Python script on each saved change:

war python app.py

Or your NodeJS script:

war node app.js