Three tools that I think are less widely known compared to how useful they are: jq, progress, and pv.

`pv` (pipe view) is rather simple but I use it for viewing a lot and sometimes rate-limiting transfers. Usage is simple: `curl huge-file | pv | some-operation` will show you the progress (okay, curl already does... but pv works for any pipe input, and pv can work in line mode with -l so you can see how many lines (records, presumably) it processed).

`progress` is even simpler! Just type progress in a random terminal while, in another, you are running an operation like cp, gzip, etc.

    $ progress
    [10123] bzip2 /tmp/test
            32.5% (127.0 MiB / 390.6 MiB)

Use -m to monitor instead of doing a one-shot. This will also allow it to calculate the remaining time (for anything running at more than a few kilobytes per second).

I also love progress just because it's such a hack. It hooks into the process and monitors file operations. Simple but effective. Somehow it works super well because it manages to ignore everything irrelevant and only shows you the file handle you care about (you can give it hints if necessary, I've used that maybe once in ten years).

`jq` takes JSON data and either pretty-prints (default) or operates on it:

    $ echo '{"whoami": "root"}' | jq
    {
      "whoami": "root"
    }
    # imagine colored output above

    $ echo '{"whoami": "root"}' | jq .whoami
    "root"

    $ echo '{"users": [{"name": "abc", ...}, ...]}' | jq '.users[].name'
    # prints the name of all users in this array

    $ curl localhost/api/v1/users | jq '.users[] | "\(.name) \(.age)"' | sort -n -k 2 | tail -1 && echo "is our oldest user!"