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Thomas G. Lockhart authored
capabilities of specifying time zones as intervals per SQL9x. Put refentrytitle contents on the same line as the tag. Otherwise, leading whitespace is propagated into the product, which (at least) messes up the ToC layout. Remove (some) docinfo tags containing dates. Best to omit if the dates are not accurate; maybe use CVS dates instead or leave them out.
Thomas G. Lockhart authoredcapabilities of specifying time zones as intervals per SQL9x. Put refentrytitle contents on the same line as the tag. Otherwise, leading whitespace is propagated into the product, which (at least) messes up the ToC layout. Remove (some) docinfo tags containing dates. Best to omit if the dates are not accurate; maybe use CVS dates instead or leave them out.
ecpg-ref.sgml 10.81 KiB
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$Header: /cvsroot/pgsql/doc/src/sgml/ref/ecpg-ref.sgml,v 1.19 2002/04/21 19:02:39 thomas Exp $
PostgreSQL documentation
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<refentry id="APP-ECPG">
<refmeta>
<refentrytitle id="app-ecpg-title"><application>ecpg</application></refentrytitle>
<manvolnum>1</manvolnum>
<refmiscinfo>Application</refmiscinfo>
</refmeta>
<refnamediv>
<refname>
<application>ecpg</application>
</refname>
<refpurpose>
embedded SQL C preprocessor
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<refsynopsisdivinfo>
<date>1999-07-20</date>
</refsynopsisdivinfo>
<cmdsynopsis>
<command>ecpg</command>
<arg choice="opt">-v</arg>
<arg choice="opt">-t</arg>
<arg choice="opt">-I <replaceable>include-path</replaceable></arg>
<arg choice="opt">-o <replaceable>outfile</replaceable></arg>
<arg choice="plain" rep="repeat"><replaceable>file</replaceable></arg>
</cmdsynopsis>
<refsect2 id="R2-APP-ECPG-1">
<refsect2info>
<date>1999-07-20</date>
</refsect2info>
<title>
Inputs
</title>
<para>
<application>ecpg</application> accepts the following command
line arguments:
<variablelist>
<varlistentry>
<term>-v</term>
<listitem>
<para>
Print version information.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-t</term>
<listitem>
<para>
Turn on auto-commit of transactions. In this mode, each query is
automatically committed unless it is inside an explicit
transaction block. In the default mode, queries are committed
only when <command>exec sql commit</command> is issued.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-I <replaceable class="parameter">include-path</replaceable></term>
<listitem>
<para>
Specify an additional include path. Defaults are <filename>.</filename> (current directory),
<filename>/usr/local/include</filename>, the
<productname>PostgreSQL</productname> include path which is
defined at compile time (default:
<filename>/usr/local/pgsql/include</filename>), and
<filename>/usr/include</filename>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-o <replaceable>outfile</replaceable></term>
<listitem>
<para>
Specifies that <application>ecpg</application> should write all its output to <replaceable>outfile</replaceable>.
If no such option is given the output is written to
<filename><replaceable>name</replaceable>.c</filename>,
assuming the input file was
named <filename><replaceable>name</replaceable>.pgc</filename>.
If the input file does have the expected
<literal>.pgc</literal> suffix, then the output file will have
<literal>.pgc</literal> appended to the input file name.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">file</replaceable></term>
<listitem>
<para>
The files to be processed.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect2>
<refsect2 id="R2-APP-ECPG-2">
<refsect2info>
<date>1998-11-05</date>
</refsect2info>
<title>
Outputs
</title>
<para>
<application>ecpg</application> will create a file or
write to <filename>stdout</filename>.
<variablelist>
<varlistentry>
<term>Return value</term>
<listitem>
<para>
<application>ecpg</application> returns 0 to the shell on successful completion, non-zero
for errors.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect2>
</refsynopsisdiv>
<refsect1 id="R1-APP-ECPG-description">
<title>Description</title>
<para>
<application>ecpg</application>
is an embedded SQL preprocessor for the C language and the
<productname>PostgreSQL</productname>. It enables development of C programs with embedded SQL code.
</para>
<para>
Linus Tolke (<email>linus@epact.se</email>) was the
original author of <application>ecpg</application> (up to version 0.2).
Michael Meskes (<email>meskes@debian.org</email>)
is the current author and maintainer of <application>ecpg</application>.
Thomas Good (<email>tomg@q8.nrnet.org</email>)
is the author of the last revision of the <application>ecpg</application> man page, on which
this document is based.
</para>
</refsect1>
<refsect1 id="R1-APP-ECPG-2">
<title>Usage</title>
<refsect2 id="R2-APP-ECPG-preprocessing">
<title>Preprocessing for Compilation</title>
<para>
An embedded SQL source file must be preprocessed before
compilation:
<synopsis>
ecpg [ -d ] [ -o <replaceable>file</replaceable> ] <replaceable>file</replaceable>.pgc
</synopsis>
where the optional <option>-d</option> flag turns on debugging.
The <literal>.pgc</literal> extension is an
arbitrary means of denoting <application>ecpg</application> source.
</para>
<para>
You may want to redirect the preprocessor output to a log file.
</para>
</refsect2>
<refsect2 id="R2-APP-ECPG-compiling">
<title>Compiling and Linking</title>
<para>
Assuming the <productname>PostgreSQL</productname> binaries are in
<filename>/usr/local/pgsql</filename>, you will need to compile
and link your preprocessed source file:
<synopsis>
gcc -g -I /usr/local/pgsql/include [ -o <replaceable>file</replaceable> ] <replaceable>file</replaceable>.c -L /usr/local/pgsql/lib -lecpg -lpq
</synopsis>
</para>
</refsect2>
</refsect1>
<refsect1 id="R1-APP-ECPG-grammar">
<title>Grammar</title>
<refsect2 id="R2-APP-ECPG-library">
<title>Libraries</title>
<para>
The preprocessor will prepend two directives to the source:
<programlisting>
#include <ecpgtype.h>
#include <ecpglib.h>
</programlisting>
</para>
</refsect2>
<refsect2 id="R2-APP-declaration">
<title>Variable Declaration</title>
<para>
Variables declared within <application>ecpg</application> source code must be prepended with:
<programlisting>
EXEC SQL BEGIN DECLARE SECTION;
</programlisting>
</para>
<para>
Similarly, variable declaration sections must terminate with:
<programlisting>
EXEC SQL END DECLARE SECTION;
</programlisting>
<note>
<para>
Prior to version 2.1.0, each variable had to be declared
on a separate line. As of version 2.1.0 multiple variables may
be declared on a single line:
<programlisting>
char foo[16], bar[16];
</programlisting>
</para>
</note>
</para>
</refsect2>
<refsect2 id="R2-APP-ECPG-errors">
<title>Error Handling</title>
<para>
The SQL communication area is defined with:
<programlisting>
EXEC SQL INCLUDE sqlca;
</programlisting>
</para>
<note>
<para>
The <literal>sqlca</literal> is in lowercase.
While SQL convention may be
followed, i.e., using uppercase to separate embedded SQL
from C statements, <literal>sqlca</literal> (which includes the <filename>sqlca.h</>
header file) <emphasis>must</> be lowercase. This is because the
EXEC SQL prefix indicates that this inclusion will be parsed by
<application>ecpg</application>.
<application>ecpg</application> observes case sensitivity
(<filename>SQLCA.h</> will not be found).
<command>EXEC SQL INCLUDE</command>
can be used to include other header files
as long as case sensitivity is observed.
</para>
</note>
<para>
The <literal>sqlprint</literal> command is used with the <literal>EXEC SQL WHENEVER</literal>
statement to turn on error handling throughout the
program:
<programlisting>
EXEC SQL WHENEVER sqlerror sqlprint;
</programlisting>
and
<programlisting>
EXEC SQL WHENEVER not found sqlprint;</programlisting>
</para>
<note>
<para>
This is <emphasis>not</emphasis> an exhaustive example of usage for
the <command>EXEC SQL WHENEVER</command> statement.
Further examples of usage may
be found in SQL manuals (e.g., <citetitle>The LAN TIMES Guide to SQL</> by
Groff and Weinberg).
</para>
</note>
</refsect2>
<refsect2 id="R2-APP-ECPG-connecting">
<title>Connecting to the Database Server</title>
<para>
One connects to a database using the following:
<programlisting>
EXEC SQL CONNECT TO <replaceable>dbname</replaceable>;
</programlisting>
where the database name is not quoted. Prior to version 2.1.0, the
database name was required to be inside single quotes.
</para>
<para>
Specifying a server and port name in the connect statement is also
possible. The syntax is:
<synopsis>
<replaceable>dbname</replaceable>[@<replaceable>server</replaceable>][:<replaceable>port</replaceable>]
</synopsis>
or
<synopsis>
<tcp|unix>:postgresql://<replaceable>server</replaceable>[:<replaceable>port</replaceable>][/<replaceable>dbname</replaceable>][?<replaceable>options</replaceable>]
</synopsis>
</para>
</refsect2>
<refsect2 id="R2-APP-ECPG-queries">
<title>Queries</title>
<para>
In general, SQL queries acceptable to other applications such as
<application>psql</application> can be embedded into your C
code. Here are some examples of how to do that.
</para>
<para>
Create Table:
<programlisting>
EXEC SQL CREATE TABLE foo (number int4, ascii char(16));
EXEC SQL CREATE UNIQUE index num1 on foo(number);
EXEC SQL COMMIT;
</programlisting>
</para>
<para>
Insert:
<programlisting>
EXEC SQL INSERT INTO foo (number, ascii) VALUES (9999, 'doodad');
EXEC SQL COMMIT;
</programlisting> </para>
<para>
Delete:
<programlisting>
EXEC SQL DELETE FROM foo WHERE number = 9999;
EXEC SQL COMMIT;
</programlisting>
</para>
<para>
Singleton Select:
<programlisting>
EXEC SQL SELECT foo INTO :FooBar FROM table1 WHERE ascii = 'doodad';
</programlisting>
</para>
<para>
Select using Cursors:
<programlisting>
EXEC SQL DECLARE foo_bar CURSOR FOR
SELECT number, ascii FROM foo
ORDER BY ascii;
EXEC SQL FETCH foo_bar INTO :FooBar, DooDad;
...
EXEC SQL CLOSE foo_bar;
EXEC SQL COMMIT;
</programlisting>
</para>
<para>
Updates:
<programlisting>
EXEC SQL UPDATE foo
SET ascii = 'foobar'
WHERE number = 9999;
EXEC SQL COMMIT;
</programlisting>
</para>
</refsect2>
</refsect1>
<refsect1 id="R1-APP-ECPG-notes">
<title>Notes</title>
<para>
The complete structure definition MUST be listed
inside the declare section.
</para>
<para>
See the <filename>TODO</filename> file in the source for some more
missing features.
</para>
</refsect1>
</refentry>
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