class="parameter">filename</replaceable> and executes it as
        though it had been typed on the keyboard.
        </para>
        <para>
        If <replaceable>filename</replaceable> is <literal>-</literal>
        (hyphen), then standard input is read until an EOF indication
        or <command>\q</command> meta-command.  This can be used to intersperse
        interactive input with input from files.  Note that Readline behavior
        will be used only if it is active at the outermost level.
        </para>
        <note>
        <para>
        If you want to see the lines on the screen as they are read you
        must set the variable <varname>ECHO</varname> to
        <literal>all</literal>.
        </para>
        </note>
        </listitem>
      </varlistentry>


      <varlistentry id="psql-metacommand-if">
        <term><literal>\if</literal> <replaceable class="parameter">expression</replaceable></term>
        <term><literal>\elif</literal> <replaceable class="parameter">expression</replaceable></term>
        <term><literal>\else</literal></term>
        <term><literal>\endif</literal></term>
        <listitem>
        <para>
        This group of commands implements nestable conditional blocks.
        A conditional block must begin with an <command>\if</command> and end
        with an <command>\endif</command>.  In between there may be any number
        of <command>\elif</command> clauses, which may optionally be followed
        by a single <command>\else</command> clause.  Ordinary queries and
        other types of backslash commands may (and usually do) appear between
        the commands forming a conditional block.
        </para>
        <para>
        The <command>\if</command> and <command>\elif</command> commands read
        their argument(s) and evaluate them as a Boolean expression.  If the
        expression yields <literal>true</literal> then processing continues
        normally; otherwise, lines are skipped until a
        matching <command>\elif</command>, <command>\else</command>,
        or <command>\endif</command> is reached.  Once
        an <command>\if</command> or <command>\elif</command> test has
        succeeded, the arguments of later <command>\elif</command> commands in
        the same block are not evaluated but are treated as false.  Lines
        following an <command>\else</command> are processed only if no earlier
        matching <command>\if</command> or <command>\elif</command> succeeded.
        </para>
        <para>
        The <replaceable class="parameter">expression</replaceable> argument
        of an <command>\if</command> or <command>\elif</command> command
        is subject to variable interpolation and backquote expansion, just
        like any other backslash command argument.  After that it is evaluated
        like the value of an on/off option variable.  So a valid value
        is any unambiguous case-insensitive match for one of:
        <literal>true</literal>, <literal>false</literal>, <literal>1</literal>,
        <literal>0</literal>, <literal>on</literal>, <literal>off</literal>,
        <literal>yes</literal>, <literal>no</literal>.  For example,
        <literal>t</literal>, <literal>T</literal>, and <literal>tR</literal>
        will all be considered to be <literal>true</literal>.
        </para>
        <para>
        Expressions that do not properly evaluate to true or false will
        generate a warning and be treated as false.
        </para>
        <para>
        Lines being skipped are parsed normally to identify queries and
        backslash commands, but queries are not sent to the server, and
        backslash commands other than conditionals
        (<command>\if</command>, <command>\elif</command>,
        <command>\else</command>, <command>\endif</command>) are
        ignored.  Conditional commands are checked only for valid nesting.
        Variable references in skipped lines are not expanded, and backquote
        expansion