How to read a block nonce in command line? I need to know how to read a block header in particular its nonce. 

How can I read a block nonce? what command line is used?
The getblock RPC command includes the nonce in its JSON output:

{
    "result": {
        "hash": "00000000c937983704a73af28acdec37b049d214adbda81d7e2a3dd146f6ed09",
        "confirmations": 543325,
        "strippedsize": 216,
        "size": 216,
        "weight": 864,
        "height": 1000,
        "version": 1,
        "versionHex": "00000001",
        "merkleroot": "fe28050b93faea61fa88c4c630f0e1f0a1c24d0082dd0e10d369e13212128f33",
        "tx": [
            "fe28050b93faea61fa88c4c630f0e1f0a1c24d0082dd0e10d369e13212128f33"
        ],
        "time": 1232346882,
        "mediantime": 1232344831,
        "nonce": 2595206198,
        "bits": "1d00ffff",
        "difficulty": 1,
        "chainwork": "000000000000000000000000000000000000000000000000000003e903e903e9",
        "previousblockhash": "0000000008e647742775a230787d66fdf92c46a48c896bfbc85cdc8acc67e87d",
        "nextblockhash": "00000000a2887344f8db859e372e7e4bc26b23b9de340f725afbf2edb265b4c6"
    },
    "error": null,
    "id": null
}


You could even pull it out of the raw hex, but bitcoind will do the heavy lifting for you here.