returned to indicate
   success or failure of the transfer.  Its status will be
   <literal>PGRES_COMMAND_OK</literal> for success or
   <literal>PGRES_FATAL_ERROR</literal> if some problem was encountered.
   At this point further SQL commands can be issued via
   <xref linkend="libpq-PQexec"/>.  (It is not possible to execute other SQL
   commands using the same connection while the <command>COPY</command>
   operation is in progress.)
  </para>

  <para>
   If a <command>COPY</command> command is issued via
   <xref linkend="libpq-PQexec"/> in a string that could contain additional
   commands, the application must continue fetching results via
   <xref linkend="libpq-PQgetResult"/> after completing the <command>COPY</command>
   sequence.  Only when <xref linkend="libpq-PQgetResult"/> returns
   <symbol>NULL</symbol> is it certain that the <xref linkend="libpq-PQexec"/>
   command string is done and it is safe to issue more commands.
  </para>

  <para>
   The functions of this section should be executed only after obtaining
   a result status of <literal>PGRES_COPY_OUT</literal> or
   <literal>PGRES_COPY_IN</literal> from <xref linkend="libpq-PQexec"/> or
   <xref linkend="libpq-PQgetResult"/>.
  </para>

  <para>
   A <structname>PGresult</structname> object bearing one of these status values
   carries some additional data about the <command>COPY</command> operation
   that is starting.  This additional data is available using functions
   that are also used in connection with query results:

   <variablelist>
    <varlistentry id="libpq-PQnfields-1">
     <term><function>PQnfields</function><indexterm
     ><primary>PQnfields</primary><secondary>with COPY</secondary></indexterm></term>

     <listitem>
      <para>
       Returns the number of columns (fields) to be copied.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry id="libpq-PQbinaryTuples-1">
     <term><function>PQbinaryTuples</function><indexterm
     ><primary>PQbinaryTuples</primary><secondary>with COPY</secondary></indexterm></term>

     <listitem>
      <para>
       0 indicates the overall copy format is textual (rows separated by
       newlines, columns separated by separator characters, etc.).  1
       indicates the overall copy format is binary.  See <xref
       linkend="sql-copy"/> for more information.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry id="libpq-PQfformat-1">
     <term><function>PQfformat</function><indexterm
     ><primary>PQfformat</primary><secondary>with COPY</secondary></indexterm></term>

     <listitem>
      <para>
       Returns the format code (0 for text, 1 for binary) associated with
       each column of the copy operation.  The per-column format codes
       will always be zero when the overall copy format is textual, but
       the binary format can support both text and binary columns.
       (However, as of the current implementation of <command>COPY</command>,
       only binary columns appear in a binary copy; so the per-column
       formats always match the overall format at present.)
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>

  <sect2 id="libpq-copy-send">
   <title>Functions for Sending <command>COPY</command> Data</title>

   <para>
    These functions are used to send data during <literal>COPY FROM
    STDIN</literal>.  They will fail if called when the connection is not in
    <literal>COPY_IN</literal> state.
   </para>

   <variablelist>
    <varlistentry id="libpq-PQputCopyData">
     <term><function>PQputCopyData</function><indexterm><primary>PQputCopyData</primary></indexterm></term>

     <listitem>
      <para>
       Sends data to the server during <literal>COPY_IN</literal> state.
<synopsis>
int PQputCopyData(PGconn *conn,
                  const char *buffer,
                  int nbytes);
</synopsis>
      </para>

      <para>
       Transmits the <command>COPY</command> data in the specified
       <parameter>buffer</parameter>,