ecpg [ -v ] [ -t ] [ -I include-path ] [ -o outfile ] file1 [ file2 ] [ ... ]
Pass this parameter to print ecpg's version information.
Pass this parameter to disable auto-transaction mode.
Use this parameter to start epcg with an additional include path. By default, it will examine the ./, /usr/local/include, PostgreSQL's defined include path, and /usr/include.
Passing this parameter specifies that ecpg will write all output to file; if no specific filename is given, output will be sent to name.c, where name is the name of the input file.
This parameter takes the name of file(s) you wish to process.
The ecpg program is an embedded C preprocessor; use it to embed SQL code within C language code.
You must preprocess a file with embedded SQL code before it can be properly compiled:
ecpg [ -d ] [ -o file ] file.pgcUsing the -d flag turns on debugging. The file extension .pgc is an arbitrary ecpg source identifier; you can use whateve extension you desire.
|Keep a log|
Use >> to redirect output to a file if you wish to keep a log.
The preprocesser adds two header directives to the beginning of your C source file:
#include <ecpgtype.h> #include <ecpglib.h>
To declare varaibles within ecpg source code, begin them with the following:
EXEC SQL BEGIN DECLARE SECTION;
To terminate a variable declaration section, use:
EXEC SQL END DECLARE SECTION;
You can declare multiple variables on a single line by using a comma to separate their declarations, such as:
char var1(16), var2(16);
Define the SQL communications area with:
EXEC SQL INCLUDE sqlca;
You must enter sqlca in lowercase, as it will be interpreted literally as the header file name, and ecpg observes case sensitivity.
Use the sqlprint command with EXEC SQL WHENEVER to turn on error handling:
EXEC SQL WHENEVER sqlerror sqlprint;and
EXEC SQL WHENEVER not found sqlprint;
There are many more ways to use the EXEC SQL WHENEVER statement. For more examples on its usage, refer to an SQL manual.
If your database is local, use the following example to connect to the backend process running it:
EXEC SQL CONNECT dbname;
If you are connecting a database hosted remotes, the following example explains the eyntax used to enter a hostname and port:
The ecpg preprocessor generally accepts most SQL statements that are acceptable by programs such as psql. Various examples of how this is done can be found below.
Creating a table:
EXEC SQL CREATE TABLE mytable (ascii char(16), number int4, number2 int4); EXEC SQL CREATE UNIQUE index index1 on mytable (number); EXEC SQL CREATE index index2 on mytable (number2); EXEC SQL COMMIT;
EXEC SQL INSERT INTO mytable (ascii, number, number 2) VALUES ('stuff', 10, 110); EXEC SQL COMMIT;
EXEC SQL DELETE FROM mytable WHERE number = 10; EXEC SQL COMMIT;
Querying with select:
EXEC SQL SELECT mytable INTO :somevariable FROM anothertable WHERE ascii = 'stuff';
Select using Cursors:
EXEC SQL DECLARE mycursor CURSOR FOR SELECT ascii, number, number2 FROM ORDER BY number; EXEC SQL FETCH mycursor INTO :somevariable, someothervariable; ... EXEC SQL CLOSE mycursor; EXEC SQL COMMIT;
EXEC SQL UPDATE mytable SET ascii = 'otherstuff' WHERE number = 10; EXEC SQL COMMIT;