detect key conflict in a JSON file

[Jabba Laci]

Hi,

How can you detect if a key is duplicated in a JSON file? Example:

{
    "something": [...],
    ...
    "something": [...]
}

I have a growing JSON file that I edit manually and it might happen
that I repeat a key. If this happens, I would like to get notified.
Currently the value of the second key silently overwrites the value of
the first.

Do you know about a command line JSON validator?

Thanks,

Laszlo