Could not able to pipe with background geth process

Question

I am working on a bash script, where it will send my commands to geth through a simple piping. The problem is for each piping I have to create geth process again, which preload my_script.js into geth all over again and this process actually consumes time since my_script.js is large.

echo "net" | sudo geth --datadir --preload "my_script.js" \
      "/home/MyEthereumEbloc" attach ipc:/home/MyEthereumEbloc/geth.ipc

Output (I can obtain the output correctly):

>
{
  listening: true,
  peerCount: 2,
  version: "23422",
  getListening: function(callback),
  getPeerCount: function(callback),
  getVersion: function(callback)
}

I want to pass information as input and get its output result from geth process that works at the background and required to load my_script.js only one time. In order to accomplish this, I have tried piping but I wasn't able to make it work. I am sorry if this question might be related to unix but any additional approach to solve this problem would be appreciated.

mkfifo program.pipe;
cat > program.pipe &
sudo geth --datadir "/home/MyEthereumEbloc" attach \
      ipc:/home/MyEthereumEbloc/geth.ipc console >> output.txt < sudo program.pipe

#On another terminal.
printf "%s\n" "net" >> sudo program.pipe

Thank you for your valuable time and help.

Answer 1

Take out the sudo in sudo program.pipe.

What's happening is that you're piping data into sudo which is baffled and does nothing. It never gets to the pipe in the first place.

Also, why are you using sudo with geth attach? This is almost certainly some kind of mistake--geth doesn't need root priviledges.

Answer 2

If you just want to get information from Geth, then you should be using the IPC or RPC interface. To access the RPC interface, you can use curl, as in

curl -X POST --data '{"jsonrpc":"2.0","method":"net_version","params":[],"id":67}'

{ "id":67, "jsonrpc": "2.0", "result": "59" }

For IPC, you can use socat to open concatenate the ipc socket to stdin:

socat "/home/MyEthereumEbloc/geth.ipc" -

or you can concat it to a named FIFO pipe for easy access:

mkfifo myPipe
socat  "/home/MyEthereumEbloc/geth.ipc" myPipe
cat myPipe
echo '{"jsonrpc":"2.0","method":"web3_clientVersion","params":[],"id":67}' >> myPipe

and then just use it like any unix fifo named pipe.