What's the easiest/fastest way to experiment with bitcoin-cli? I want to experiment with the bitcoin-cli in the easiest way.
I just installed bitcoin core and waiting for it to download the blockchain.
Is there a way meanwhile I can run bitcoind and/or bitcoin-cli, that doesn't require downloading the whole blockchain?
I guess running the test-net is a natural approach.
My main problem is: I don't see the bitcoind and bitcoin-cli executables anywhere on my system.
I'm running Ubuntu 16.04.1 LTS
and installed bitcoin core through the command line as described here:
http://bitzuma.com/posts/getting-started-with-bitcoin-core-on-ubuntu/

ultimately running bitcoin-qt from the command line.
Yes, you can run bitcoind with the -testnet option.  This starts a separate process that runs independently of the mainnet bitcoind.  You can control it with bitcoin-cli -testnet.

Note that you will have to download and verify the testnet blockchain before being able to do very much.  This also takes some time / bandwidth / disk space / CPU, though much less than for mainnet.  Depending on the speed of your CPU and Internet connection, it might also make the mainnet download take longer if they have to share resources.