Command line example of adding file picture.jpg to Stream 'Photo'

Question

Hi,

Could someone please help me with the steps (Commands) to add File to a Stream?

I have setup the chain, added nodes, published items in the streams. Now I am looking to add files directly to the Blockchain.

Rahul

Answer 1

You would need to get the file contents in hexadecimal form, then pass it as a parameter to the publish command. If you are using bash on Linux, this is an example:

multichain-cli chain1 publish stream1 file1 `xxd -p README.txt | tr -d '\n'`

You need to substitute as appropriate:

• chain1 for your blockchain name
• stream1 for your stream name
• file1 for the stream item key
• README.txt for the file name

If you get an error from bash about the argument list being too long, you'll need to do this via the JSON-RPC API instead.

Comments

Thanks for a prompt response.

Any idea how we can achieve this in Windows Environment?

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Windows has an equivalent of the ` backtick operator, which lets you use a file contents as a command-line parameter - see here: http://stackoverflow.com/questions/2768608/batch-equivalent-of-bash-backticks

As for the conversion from binary to hexadecimal, you would probably want to do that in a separate stage - apparently there's a certutil command you can use:

http://stackoverflow.com/questions/4648118/converting-a-binary-file-to-hex-representation-using-batch-file

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multichain-cli abc publish names file1 ‘for /f "usebackq tokens=*" %a in (fbireadme.hex) do @echo %a %I`

Tried the above on Windows machine. Unable to get it working.


Error:
error code:  -1
error message: publish "stream-identifier" "key" data-hex

Published Stream Item

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I think the 'for' syntax is different, and you need to start with the 'for', then use the $ parameter within the final command line afterwards. Please take a look at some of the examples in the links posted above.

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Thanks for all you help team.

for /f "usebackq tokens=*" %a in (readme.hex) do @echo %a | multichain-cli abc publish names Var1 %a

This is what finally worked for me.

Cheers,
Rahul

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As for the Certutil, it does convert from ASCII to Hex, but the output file has line number, ASCII table and spaces.

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This might help you as well: http://www.diamondspirit.net/adunk/software/hexdump.html

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I did exactly the command line you wrote and I have still a error code: -8

What could be the solution ?

Cheers,
Paul

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See this answer: http://www.multichain.com/qa/5073/error-code-1-in-datastream?show=5090#a5090