can be activated for the
    <literal>mydb</literal> database by typing the command:
<screen>
<prompt>$</prompt> <userinput>psql mydb</userinput>
</screen>
    If you do not supply the database name then it will default to your
    user account name.  You already discovered this scheme in the
    previous section using <command>createdb</command>.
   </para>

   <para>
    In <command>psql</command>, you will be greeted with the following
    message:
<screen>
psql (&version;)
Type "help" for help.

mydb=&gt;
</screen>
    <indexterm><primary>superuser</primary></indexterm>
    The last line could also be:
<screen>
mydb=#
</screen>
    That would mean you are a database superuser, which is most likely
    the case if you installed the <productname>PostgreSQL</productname> instance
    yourself.  Being a superuser means that you are not subject to
    access controls.  For the purposes of this tutorial that is not
    important.
   </para>

   <para>
    If you encounter problems starting <command>psql</command>
    then go back to the previous section.  The diagnostics of
    <command>createdb</command> and <command>psql</command> are
    similar, and if the former worked the latter should work as well.
   </para>

   <para>
    The last line printed out by <command>psql</command> is the
    prompt, and it indicates that <command>psql</command> is listening
    to you and that you can type <acronym>SQL</acronym> queries into a
    work space maintained by <command>psql</command>.  Try out these
    commands:
    <indexterm><primary>version</primary></indexterm>
<screen>
<prompt>mydb=&gt;</prompt> <userinput>SELECT version();</userinput>
                                         version
-------------------------------------------------------------------&zwsp;-----------------------
 PostgreSQL &version; on x86_64-pc-linux-gnu, compiled by gcc (Debian 4.9.2-10) 4.9.2, 64-bit
(1 row)

<prompt>mydb=&gt;</prompt> <userinput>SELECT current_date;</userinput>
    date
------------
 2016-01-07
(1 row)

<prompt>mydb=&gt;</prompt> <userinput>SELECT 2 + 2;</userinput>
 ?column?
----------
        4
(1 row)
</screen>
   </para>

   <para>
    The <command>psql</command> program has a number of internal
    commands that are not SQL commands.  They begin with the backslash
    character, <quote><literal>\</literal></quote>.
    For example,
    you can get help on the syntax of various
    <productname>PostgreSQL</productname> <acronym>SQL</acronym>
    commands by typing:
<screen>
<prompt>mydb=&gt;</prompt> <userinput>\h</userinput>
</screen>
   </para>

   <para>
    To get out of <command>psql</command>, type:
<screen>
<prompt>mydb=&gt;</prompt> <userinput>\q</userinput>
</screen>
    and <command>psql</command> will quit and return you to your
    command shell. (For more internal commands, type
    <literal>\?</literal> at the <command>psql</command> prompt.)  The
    full capabilities of <command>psql</command> are documented in
    <xref linkend="app-psql"/>.  In this tutorial we will not use these
    features explicitly, but you can use them yourself when it is helpful.
   </para>

  </sect1>
 </chapter>