user38607: If I have many files on my hard drive (possibly with different names/extension), how can I test which file is a valid bitcoin wallet.dat ? 
Maybe there is some string that exists in every bitcoin wallet ? 
I guess I am asking about the format of the data inside the wallet. 
If wallets are different depending on the bitcoin client, then I want to know about bitcoin core.
Edit: I forgot to mention but these files WERE on a Linux OS. So there should be some solutions.

user2306: On Linux, you can use the file command. If the file is a Bitcoin wallet, you should see
wallet.dat: Berkeley DB (Btree, version 9, native byte-order)

(It will always say Berkley DB version 9, but the filename might be different.)
file is also availible on Windows: http://gnuwin32.sourceforge.net/packages/file.htm
How does file tell that it's a Berkley DB file? See How did file identify this wallet file?

38607: <p>If I have many files on my hard drive (possibly with different names/extension), how can I test which file is a valid bitcoin wallet.dat ? </p>

<p>Maybe there is some string that exists in every bitcoin wallet ? </p>

<p>I guess I am asking about the format of the data inside the wallet. 
If wallets are different depending on the bitcoin client, then I want to know about bitcoin core.</p>

<p><strong>Edit:</strong> I forgot to mention but these files WERE on a Linux OS. So there should be some solutions.</p>
 2306: <p>On Linux, you can use the <code>file</code> command. If the file is a Bitcoin wallet, you should see</p>

<pre><code>wallet.dat: Berkeley DB (Btree, version 9, native byte-order)
</code></pre>

<p>(It will always say Berkley DB version 9, but the filename might be different.)</p>

<p><code>file</code> is also availible on Windows: <a href="http://gnuwin32.sourceforge.net/packages/file.htm" rel="nofollow noreferrer">http://gnuwin32.sourceforge.net/packages/file.htm</a></p>

<p>How does <code>file</code> tell that it's a Berkley DB file? See <a href="https://unix.stackexchange.com/questions/244502/how-did-file-identify-this-particular-file">How did file identify this wallet file?</a></p>
