Bitcoin prices with a shell one-liner

Update: Coinbase has removed this API so this no longer works.

I wanted to use my intermediate-at-shell skills to get the latest bitcoin price from Coinbase. So I wrote this nasty thing:

curl -sSL https://coinbase.com/api/v1/prices/historical | head -n 1 | sed "s|^.*,|$|" | sed "s|\(\.[0-9]$\)|\10|"

I aliased it to btc and can now do this in my terminal:

btc
# $420.69

Kind of cool! If you’re interested in how I made this work…

1. First, we grab the bitcoin prices from Coinbase with curl.

    curl -sSL {{coinbase_url}} | ..
   

   We pass three arguments to curl. The lowercase s runs curl silently, and the capital S shows errors if any happen. The L flag tells curl to follow redirects, should any appear.

2. The prices from Coinbase are in a long-ass file, so we only want the first line:

    .. | head -n 1 | ..
   

   Now we’ll have an output like 2014-04-20T04:20:69-07:00,420.0. The price is in there, but we need to clean it up to make it readable.

3. Next, we use sed to remove everything up until the first comma and replace it with a dollar sign (because these prices are in USD).

    .. | sed "s|^.*,|$|" | ..
   

   Now we’ll have something like $420.0 – really close! If the price has two digits after the decimal (like $420.69), then the next step doesn’t do anything. But if so…

4. We have to make sure the decimal has two digits after it.

    .. | sed "s|\(\.[0-9]$\)|\10|"
   

   This again uses sed to find something that ends in “.1”, or “.2”, or whatever. If it finds that, it appends a zero.

I’m not an expert with scripting and pipes and all of these, so I’m sure there’s a better way to do this. But it was a fun exercise!

Happy bitcoining, nerds.