GDAX bash tool to download currency pair prices

gdax

#!/bin/bash

function perror {
	echo "$*" >&2
}

function check_dependency {
	if ! command -v $1 &> /dev/null
	then
		perror "Missing dependency: '$1'. Please install it first."
		exit 1
	fi
}

if [ $# -ne 1 ]
then
	perror "Usage: $(basename $0) <currency pair>"
	perror
	perror " * <currency pair> is a supported GDAX.COM currency pair like:"
	perror "   BTC-USD, BTC-EUR, ETH-BTC, ..."
	perror
	perror " * Example: \"$(basename $0) BTC-USD\""
	exit 2
fi

check_dependency "curl"
check_dependency "jq"
check_dependency "tr"

pair_data=$(curl -s https://api.gdax.com/products/$1/ticker)

if [ $? -ne 0 ]
then
	perror "Error while downloading currency pair data."
	perror "Please check your internet connection."
	exit 3
fi

price=$(echo $pair_data | jq '.ask' | tr -d '"')

if [ "$price" = "null" ]
then
	perror "Error processing pair data."
	perror "Please check if the currency pair is supported by GDAX.COM or wrongly spelled."
	exit 3
fi

echo $price