title: install_name_tool difference between -change and -id
body: <p>I have been struggling with this concept for a while and I cannot really understand what the difference is between <code>-change</code> and <code>-id</code>.The man page states</p>
  
  <pre><code> -id name
                Changes  the  shared  library identification name of a dynamic shared library to name.  If the Mach-O binary is not a dynamic
                shared library and the -id option is specified it is ignored.
  
  -change old new
                Changes  the dependent shared library install name old to new in the specified Mach-O binary.  More than one of these options
                can be specified.  If the Mach-O binary does not contain the old install name in a specified -change  option  the  option  is
                ignored.
  </code></pre>
  
  <p>So far I have experimented with <code>-change</code>. Suppose I have the following structure</p>
  
  <pre><code>Test.App
  |_Contents
      |_MacOS
      |   |_test -----&gt; item A
      |_Library
          |_test_library.dylib     ---&gt;item B
          |_another_library.dylib  ---&gt;item C
  </code></pre>
  
  <p>Now suppose I ran the following on itemB</p>
  
  <pre><code>$ otool -L test_library.dylib
     test_library.dylib
     /some/path/another_library.dylib  --&gt;item D
  </code></pre>
  
  <p>The above result indicates that <code>test_library.dylib</code> depends on <code>another_library.dylib</code> now if I needed to change the location of <code>another_library.dylib</code> I would do this</p>
  
  <pre><code>install_name_tool -change /some/path/another_library.dylib some/new/path/another_library.dylib  test_library.dylib 
  </code></pre>
  
  <p>this would change the location of item D. My question is what does <code>install-name_tool -id</code> do and when do I use that ?</p>