Abuse cURL to communicate with Redis

I want to send a PING to Redis to check if the connection is working, now I could just install redis-cli, but I don't want to and curl is already there. So how can I abuse curl to do that? Basically I need to turn off what's send here:

> GET / HTTP/1.1
> User-Agent: curl/7.22.0 (x86_64-pc-linux-gnu) libcurl/7.22.0 OpenSSL/1.0.1 zlib/1.2.3.4 libidn/1.23 librtmp/2.3
> Host: localhost:6379
> Accept: */*
> 
-ERR wrong number of arguments for 'get' command
-ERR unknown command 'User-Agent:'
-ERR unknown command 'Host:'
-ERR unknown command 'Accept:'

I was able to get rid of the User-Agent altogether by adding -A "", but I can't find anything else for the rest. Any idea how I can do that?

When you want to use curl, you need REST over RESP, like webdis, tinywebdis or turbowebdis. See https://github.com/markuman/tinywebdis#turbowebdis-tinywebdis--cherrywebdis

$ curl -w '\n' http://127.0.0.1:8888/ping
{"ping":"PONG"}

Without a REST interface for redis, you can use netcat for example.

$ (printf "PING\r\n";) | nc <redis-host> 6379 
+PONG

For password protected redis you can use netcat like this:

$ (printf "AUTH <password>\r\n";) | nc <redis-host> 6379
+PONG

With netcat you have to build the RESP protocol by your self. See http://redis.io/topics/protocol

update 2018-01-09

I've build a powerfull bash function which pings the redis instance at any cost over tcp

    function redis-ping() {
            # ping a redis server at any cost
            redis-cli -h $1 ping 2>/dev/null || \
                    echo $((printf "PING\r\n";) | nc $1 6379 2>/dev/null || \
                    exec 3<>/dev/tcp/$1/6379 && echo -e "PING\r\n" >&3 && head -c 7 <&3)
    }

usage redis-ping localhost

Not curl, but doesn't require a HTTP interface or nc (great for something like a container where you don't have nc installed)

exec 3<>/dev/tcp/127.0.0.1/6379 && echo -e "PING\r\n" >&3 && head -c 7 <&3

Should give you

+PONG

You can read more about what's going on from this fantastic article.

I needed to add a sleep to the nc provided by @Markus to get it to work from a remote system:

(printf "PING\r\n"; sleep 1) | nc remote.redis.hostname 6379

See Request/Response protocols and RTT: Redis Pipelining for details.