ecpg - Embedded SQL C preprocessor
SYNOPSIS
ecpg [ -v ] [ -t ] [ -I include-path ] [ -o outfile ] file1 [ file2 ] [ ... ]
INPUTS
ecpg accepts the following command line arguments:
-v Print version information.
-t Turn off auto-transaction mode.
-I path
Specify an additional include path. Defaults are
., /usr/local/include, the Postgres include path
which is defined at compile time (default:
/usr/local/pgsql/lib), and /usr/include.
-o Specifies that ecpg should write all its output to
outfile. If no such option is given the output is
written to name.c, assuming the input file was
named name.pgc. If the input file does have the
expected .pgc suffix, then the output file will
have .pgc appended to the input file name.
file The files to be processed.
OUTPUTS
ecpg will create a file or write to stdout.
return value
ecpg returns 0 to the shell on successful comple
tion, -1 for errors.
DESCRIPTION
ecpg is an embedded SQL preprocessor for the C language
and the Postgres. It enables development of C programs
with embedded SQL code.
Linus Tolke (<linus@epact.se>) was the original author of
ecpg (up to version 0.2). Michael Meskes
(<meskes@debian.org>) is the current author and maintainer
of ecpg. Thomas Good (<tomg@q8.nrnet.org>) is the author
of the last revision of the ecpg man page, on which this
document is based.
USAGE
PREPROCESSING FOR COMPILATION
An embedded SQL source file must be preprocessed before
ecpg [ -d ] [ -o file ] file.pgc
where the optional -d flag turns on debugging. The .pgc
extension is an arbitrary means of denoting ecpg source.
You may want to redirect the preprocessor output to a log
file.
COMPILING AND LINKING
Assuming the Postgres binaries are in /usr/local/pgsql,
you will need to compile and link your preprocessed source
file:
gcc -g -I /usr/local/pgsql/include [ -o file ] file.c -L /usr/local/pgsql/lib -lecpg -lpq
GRAMMAR
LIBRARIES
The preprocessor will prepend two directives to the
source:
#include <ecpgtype.h>
#include <ecpglib.h>
VARIABLE DECLARATION
Variables declared within ecpg source code must be
prepended with:
EXEC SQL BEGIN DECLARE SECTION;
Similarly, variable declaration sections must terminate
with:
EXEC SQL END DECLARE SECTION;
Note: 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:
char foo(16), bar(16);
The SQL communication area is defined with:
EXEC SQL INCLUDE sqlca;
Note: The sqlca is in lowercase. While SQL conven
tion may be followed, i.e., using uppercase to sep
arate embedded SQL from C statements, sqlca (which
includes the sqlca.h header file) MUST be lower
case. This is because the EXEC SQL prefix indicates
that this INCLUDE will be parsed by ecpg. ecpg
observes case sensitivity (SQLCA.h will not be
found). EXEC SQL INCLUDE can be used to include
other header files as long as case sensitivity is
observed.
The sqlprint command is used with the EXEC SQL WHENEVER
statement to turn on error handling throughout the pro
gram:
EXEC SQL WHENEVER sqlerror sqlprint;
and
EXEC SQL WHENEVER not found sqlprint;
Note: This is not an exhaustive example of usage
for the EXEC SQL WHENEVER statement. Further exam
ples of usage may be found in SQL manuals (e.g.,
`The LAN TIMES Guide to SQL' by Groff and Wein
berg).
CONNECTING TO THE DATABASE SERVER
One connects to a database using the following:
EXEC SQL CONNECT TO dbname;
where the database name is not quoted. Prior to version
2.1.0, the database name was required to be inside single
quotes.
Specifying a server and port name in the connect statement
is also possible. The syntax is:
dbname[@server][:port]
<tcp|unix>:postgresql://server[:port][/dbname][?options]
QUERIES
In general, SQL queries acceptable to other applications
such as psql can be embedded into your C code. Here are
some examples of how to do that.
Create Table:
EXEC SQL CREATE TABLE foo (number int4, ascii char(16));
EXEC SQL CREATE UNIQUE index num1 on foo(number);
EXEC SQL COMMIT;
Insert:
EXEC SQL INSERT INTO foo (number, ascii) VALUES (9999, 'doodad');
EXEC SQL COMMIT;
Delete:
EXEC SQL DELETE FROM foo WHERE number = 9999;
EXEC SQL COMMIT;
Singleton Select:
EXEC SQL SELECT foo INTO :FooBar FROM table1 WHERE ascii = 'doodad';
Select using Cursors:
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;
Updates:
EXEC SQL UPDATE foo
SET ascii = 'foobar'
EXEC SQL COMMIT;
NOTES
There is no EXEC SQL PREPARE statement.
The complete structure definition MUST be listed inside
the declare section.
See the TODO file in the source for some more missing fea
tures.
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