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 <chapter id="pgeasy-chapter">
  <title id="pgeasy">libpgeasy - Simplified C Binding Library</title>

  <note>
   <title>Author</title>

   <para>
    Written by Bruce Momjian
    (<ulink url="mailto:pgman@candle.pha.pa.us">pgman@candle.pha.pa.us</ulink>)
    and last updated 2000-03-30.
   </para>
  </note>

  <para>
   <productname>pgeasy</productname> allows you to cleanly interface
   to the <productname>libpq</productname> library,
   more like a 4GL SQL interface.
  </para>

  <para>
   It consists of set of simplified C functions that encapsulate the
   functionality of libpq.
   The functions are:

   <itemizedlist>
    <listitem>
     <para>
PGresult   *doquery(char *query);
     </para>
    </listitem>

    <listitem>
     <para>
PGconn     *connectdb(char *options);
     </para>
    </listitem>

    <listitem>
     <para>
void        disconnectdb();
     </para>
    </listitem>

    <listitem>
     <para>
int         fetch(void *param,...);
     </para>
    </listitem>

    <listitem>
     <para>
int         fetchwithnulls(void *param,...);
     </para>
    </listitem>

    <listitem>
     <para>
void        reset_fetch();
     </para>
    </listitem>

    <listitem>
     <para>
void        on_error_continue();
     </para>
    </listitem>

    <listitem>
     <para>
void        on_error_stop();
     </para>
    </listitem>

    <listitem>
     <para>
PGresult   *get_result();
     </para>
    </listitem>

    <listitem>
     <para>
void        set_result(PGresult *newres);
     </para>
    </listitem>

    <listitem>
     <para>
void        unset_result(PGresult *oldres);
     </para>
    </listitem>
   </itemizedlist>
  </para>

  <para>
   Many functions return a structure or value, so you can do more work
   with the result if required.
  </para>

  <para>
   You basically connect to the database with <function>connectdb</function>,
   issue your query with <function>doquery</function>,
   fetch the results with <function>fetch</function>,
   and finish with <function>disconnectdb</function>.
  </para>

  <para>
   For <literal>SELECT</literal> queries, <function>fetch</function>
   allows you to pass pointers as parameters, and on return the variables
   are filled with data from the binary cursor you opened.  These binary
   cursors can not be used if you are running the
   <productname>pgeasy</productname>
   client on a system with a different architecture than the database
   server.  If you pass a NULL pointer parameter, the column is skipped.
   <function>fetchwithnulls</function> allows you to retrieve the NULL
   status of the field by passing an <literal>int*</literal>
   after each result pointer, which returns true or false if the field is null.
   You can always use libpq functions on the PGresult pointer returned
   by <function>doquery</function>.
   <function>reset_fetch</function> starts the fetch back at the beginning.
  </para>

  <para>
   <function>get_result</function>,
   <function>set_result</function>,
   and
   <function>unset_result</function>
   allow you to handle multiple result sets at the same time.
  </para>

  <para>
   There are a variety of demonstration programs in the
   source directory.
  </para>
 </chapter>

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