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<!--
$Header: /cvsroot/pgsql/doc/src/sgml/Attic/libpgeasy.sgml,v 2.9 2002/03/04 18:50:20 momjian Exp $
-->
<chapter id="pgeasy">
<title><application>libpgeasy</application> - Simplified C Library</title>
<note>
<title>Author</title>
<para>
Written by Bruce Momjian
(<email>pgman@candle.pha.pa.us</email>)
and last updated 2002-03-04
</para>
</note>
<para>
<application>pgeasy</application> allows you to cleanly interface
to the <application>libpq</application> library, more like a 4GL
SQL interface. Refer to <xref linkend="libpq"> for more
information about <application>libpq</application>.
</para>
<para>
It consists of a set of simplified C functions that encapsulate the
functionality of <application>libpq</application>. The functions are:
<itemizedlist>
<listitem>
<synopsis>
PGresult *doquery(char *query);
</synopsis>
</listitem>
<listitem>
<synopsis>
PGconn *connectdb(char *options);
</synopsis>
</listitem>
<listitem>
<synopsis>
void disconnectdb();
</synopsis>
</listitem>
<listitem>
<synopsis>
int fetch(void *param,...);
</synopsis>
</listitem>
<listitem>
<synopsis>
int fetchwithnulls(void *param,...);
</synopsis>
</listitem>
<listitem>
<synopsis>
void reset_fetch();
</synopsis>
</listitem>
<listitem>
<synopsis>
void on_error_continue();
</synopsis>
</listitem>
<listitem>
<synopsis>
void on_error_stop();
</synopsis>
</listitem>
<listitem>
<synopsis>
PGresult *get_result();
</synopsis>
</listitem>
<listitem>
<synopsis>
void set_result(PGresult *newres);
</synopsis>
</listitem>
</itemizedlist>
</para>
<para>
Many functions return a structure or value, so you can 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 cannot be used if you are running the
<application>pgeasy</application> 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 to indicate if the field is null. You can always use
<application>libpq</application> functions on the
<structname>PGresult</structname> pointer returned by
<function>doquery</function>. <function>reset_fetch</function> starts
the fetch back at the beginning.
</para>
<para>
<function>get_result</function> and <function>set_result</function>
allow you to handle multiple open result sets. Use
<function>get_result</function> to save a result into an application
variable. You can then later use <function>set_result</function> to
return to the previously save result.
</para>
<para>
There are several demonstration programs in
<filename>pgsql/src/interfaces/libpgeasy/examples</>.
</para>
</chapter>
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