title: How to escape a "su -c 'psql ... -c \"\"' " with reserved words
body: <p>The reserved word 'user' is the problem for me, because it should be escaped with "" (double quotes) but with the combination of different quotes (' and " and \' and "/) psql passes it as user (without double escape). How to get this special word escaped?</p>
  
  <p>I've tried already using $$ (Dollar-Quoted String Constants) or putting it in different variables, but nothing helps.</p>
  
  <pre class="lang-sh prettyprint-override"><code>DB=mydb
  
  MAIL_USER=my@mail.de
  MAIL_PASS=password
  MAIL_SERVER=mail.server.de
  MAIL_PORT_IMAP=993
  MAIL_PORT_SMTP=465
  
  su -c "psql -d $DB -c \"INSERT INTO fetchmail_server(name, \"user\", type, server, port, is_ssl, password, active, priority, state, original) SELECT '$MAIL_USER', '$MAIL_USER', 'imap', '$MAIL_SERVER', $MAIL_PORT_IMAP, True, '$MAIL_PASS', True, 1, 'done', True WHERE NOT EXISTS (SELECT 1 FROM fetchmail_server WHERE name='$MAIL_USER')\"" postgres
  </code></pre>
  
  <p>Expected result would be, that this command is executed in the database</p>
  
  <pre><code>INSERT INTO fetchmail_server(name, "user", type, server, port, is_ssl, password, active, priority, state, original) SELECT 'my@mail.de', 'my@mail.de', 'imap', 'mail.server.de', 993, True, 'password', True, 1, 'done', True WHERE NOT EXISTS (SELECT 1 FROM fetchmail_server WHERE name='my@mail.de')
  </code></pre>