title: How to install Postgres server-side (backend) header files for an already-installed version of Postgres
body: <p>I recently upgraded to Postgres 9.5 simply by installing from Ubuntu package repos. Everything went smoothly in the upgrade and I regularly use Postgres and all my previous data.</p>
  
  <p>However, I am also working on some C language extensions and need to import the backend header "postgres.h" -- which is not found in the Postgres include dir.</p>
  
  <p>The <a href="https://www.postgresql.org/docs/9.5/static/install-procedure.html" rel="nofollow">documentation</a> (search for 'server header files' and read the note) suggests that there should be private subdirectories under the base include directory and that server-side headers will be installed there, but this is not the case for me.</p>
  
  <p>Using <code>find</code> to search the entire machine for "postgres.h" reveals that the only copy is in a separate directory where I downloaded an older version of the Postgres source just for reading and searching code -- not at all for supporting an installation.</p>
  
  <p>I want to avoid rebuilding or reinstalling Postgres at all costs, as everything is working fine. I just need to make the headers available.</p>