I asked Ella to write me a command-line program to do currency
conversion. A few minutes later, she handed me this:

#!/bin/sh

if [ $# -ne 3 ] ; then
    echo usage: $(basename $0) amount from to > /dev/stderr
    exit 64
fi

amount=$1
from=$(echo $2 | tr a-z A-Z)
to=$(echo $3 | tr a-z A-Z)

curl -s https://api.fixer.io/latest?base=${from}\&symbols=${to} |
        jq ".rates.${to} * ${amount}"