<p>The block hash identifies a block. A block can contain multiple transactions, so <code>listsinceblock</code> lists all transactions in blocks newer than the given block hash.</p>

<p>So f.e., if you have this block structure:</p>

<pre><code>block 5 hash: qwertyyuiop
|   tx100,tx101,tx102,tx103
v
block 6 hash: asdfghjklkl
|   tx104,tx105,tx106,tx107,tx108
v
block 7 hash: zxcvbnmnbvc
    tx109,tx110,tx111
</code></pre>

<p>When you would do <code>listsinceblock qwertyyuiop</code>, you would get all transactions in blocks older than block 5, so <code>tx104</code> all the way up to <code>tx111</code>.</p>

CC BY-SA 3.0
2013-05-08T13:09:47.143Z
How long one block hash last? So how often is block hash changed?
gorgi93
CC BY-SA 3.0
2013-05-08T17:52:22.370Z
The hash of a block does never change. It's its identifier, every block has a unique block hash.
Steven Roose
CC BY-SA 3.0
2013-05-06T10:42:13.603Z
2013-05-06T10:42:13.603Z
Steven Roose
<p>I am writing transaction monitoring service but I am having some problems with listing since block hash. I have bitcoind daemon and when I execute listTransactions some transactions have same block hash so if I would try to listSinceBlock I would have problems. How this all works?</p>

<client><bitcoind>
block hash and list since block?
gorgi93
# block hash and list since block?

(Asked by: username_0 on 2013-05-05)

I am writing transaction monitoring service but I am having some problems with listing since block hash. I have bitcoind daemon and when I execute listTransactions some transactions have same block hash so if I would try to listSinceBlock I would have problems. How this all works?

**Tags:** client, bitcoind


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## 1 answers

### Answer by username_1 on 2013-05-06. Score: 3 | Accepted answer

The block hash identifies a block. A block can contain multiple transactions, so listsinceblock lists all transactions in blocks newer than the given block hash.
So f.e., if you have this block structure:
block 5 hash: qwertyyuiop
|   tx100,tx101,tx102,tx103
v
block 6 hash: asdfghjklkl
|   tx104,tx105,tx106,tx107,tx108
v
block 7 hash: zxcvbnmnbvc
    tx109,tx110,tx111

When you would do listsinceblock qwertyyuiop, you would get all transactions in blocks older than block 5, so tx104 all the way up to tx111.

> **Comments:**
> **username_0**: How long one block hash last? So how often is block hash changed?  
> **username_1**: The hash of a block does never change. It's its identifier, every block has a unique block hash.  

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