title: Use srec_cat to join three binaries and fill holes
body: <p>I have three binaries for specific memory addresses that I want to combine with <code>srec_cat</code> filling the holes with 0xFF.</p>
  
  <ul>
  <li>bootloader.bin —> 0x1000</li>
  <li>conf.bin —> 0x8000</li>
  <li>app.bin —> 0x10000</li>
  </ul>
  
  <p><strong>Memory map</strong></p>
  
  <pre><code>|- pad w/ 0xFF -|- *bootloader* ~~~ pad w/ 0xFF -|- *conf* ~~~ pad w/ 0xFF -| - *app* ~~~|
  0            0x1000                           0x8000                    0x10000
  </code></pre>
  
  <p><code>~~~</code> signifies a "fluid" boundary i.e. the binary to the left of it doesn't have a fixed size.</p>
  
  <p><strong>CLI arguments</strong></p>
  
  <p>I am a bit lost between the <code>−fill</code>, <code>-binary</code> and <code>-offset</code> options that I read about on <a href="http://srecord.sourceforge.net/man/man1/srec_examples.html#BINARY%20FILES" rel="nofollow noreferrer">http://srecord.sourceforge.net/man/man1/srec_examples.html#BINARY%20FILES</a>. Is there a way to tell <code>srec_cat</code> to fill anything between 0x1000 and 0x8000 that is <strong>not</strong> occupied by <code>bootloader.bin</code> (regardless of what size the .bin actually has)?</p>