title: pg gem install fails
body: <p>Centos 6.9
  (similar to question: <a href="https://stackoverflow.com/questions/6209797/cant-find-the-postgresql-client-library-libpq">Can&#39;t find the PostgreSQL client library (libpq)</a> but that one is on MacOS not Centos, so those solutions did not work</p>
  
  <p>ruby 2.1.8 (tried 2.2)</p>
  
  <p>rails 4.2.6 (tried 5.0)</p>
  
  <p>postgres 9.3</p>
  
  <p>I am trying to install the pg gem with:</p>
  
  <pre><code>gem install pg -- --with-pqlib=/usr/lib64/libpqxx-4.0.so --with-pg-config=/usr/pgsql-9.3/bin/pg_config
  </code></pre>
  
  <p>I keep trying to feed it different libraries but the one it is getting stuck on is some <code>PQconnectdb()</code> function. Error below</p>
  
  <p>Rails used to be installed on this computer with pg but something happend after an update.. Any ideas here?</p>
  
  <pre><code>ERROR:  Error installing pg:
  ERROR: Failed to build gem native extension.
  
  current directory: /home/myusername/.rvm/gems/ruby-2.1.8/gems/pg-0.14.1/ext
  /home/myusername/.rvm/rubies/ruby-2.1.8/bin/ruby -r ./siteconf20170425-12873-191077o.rb extconf.rb --with-pqlib=/usr/lib64/libpqxx-4.0.so --with-pg-config=/usr/pgsql-9.3/bin/pg_config
  Using config values from /usr/pgsql-9.3/bin/pg_config
  extconf.rb:34: warning: Insecure world writable dir /opt/anaconda in PATH, mode 040777
  checking for libpq-fe.h... yes
  checking for libpq/libpq-fs.h... yes
  checking for pg_config_manual.h... yes
  checking for PQconnectdb() in -l/usr/lib64/libpqxx-4.0.so... no
  checking for PQconnectdb() in -llibpq... no
  checking for PQconnectdb() in -lms/libpq... no
  Can't find the PostgreSQL client library (libpq)
  *** extconf.rb failed ***
  Could not create Makefile due to some reason, probably lack of necessary
  libraries and/or headers.  Check the mkmf.log file for more details.  You may
  need configuration options.
  </code></pre>
  
  <p>Installed pg libraries:<code>Installed Packages
  postgresql93.x86_64                                   9.3.16-1PGDG.rhel6<br>
  postgresql93-contrib.x86_64                           9.3.16-1PGDG.rhel6<br>
  postgresql93-debuginfo.x86_64                         9.3.16-1PGDG.rhel6<br>
  postgresql93-devel.x86_64                             9.3.16-1PGDG.rhel6<br>
  postgresql93-docs.x86_64                              9.3.16-1PGDG.rhel6<br>
  postgresql93-libs.x86_64                              9.3.16-1PGDG.rhel6<br>
  postgresql93-odbc.x86_64                              09.06.0100-1PGDG.rhel6<br>
  postgresql93-odbc-debuginfo.x86_64                    09.03.0400-1PGDG.rhel6<br>
  postgresql93-plperl.x86_64                            9.3.16-1PGDG.rhel6<br>
  postgresql93-plpython.x86_64                          9.3.16-1PGDG.rhel6<br>
  postgresql93-pltcl.x86_64                             9.3.16-1PGDG.rhel6<br>
  postgresql93-server.x86_64                            9.3.16-1PGDG.rhel6<br>
  postgresql93-tcl.x86_64                               2.1.1-1.rhel6<br>
  postgresql93-tcl-debuginfo.x86_64                     2.1.1-1.rhel6<br>
  postgresql93-test.x86_64                              9.3.16-1PGDG.rhel6</code></p>