A simple todo program with just Unix tools

todos.sh

#!/usr/bin/env bash
command=$1
shift

# Make sure the following path is valid on your system
data_file="$HOME/.local/var/db/todos/todos.db"
temp_data_file="/tmp/todos.db.tmp"

case $command in
    add)
        echo $@ >> $data_file
        ;;
    del)
        prev_row=$(echo "$1 - 1" | bc)
        next_row=$(echo "$1 + 1" | bc)

        head -n$prev_row  $data_file  > $temp_data_file
        tail -n+$next_row $data_file >> $temp_data_file

        deleted_todo=$(head -n$1 $data_file | tail -n1)

        mv $temp_data_file $data_file
        echo "deleted: $1: $deleted_todo"
        ;;
    *)
        echo -e "Todos\n------"
        cat -n $data_file
        ;;
esac