ecpg — embedded SQL C preprocessor
ecpg [option...]
file...
ecpg is the embedded SQL preprocessor for C
programs. It converts C programs with embedded SQL statements to
normal C code by replacing the SQL invocations with special
function calls. The output files can then be processed with any C
compiler tool chain.
ecpg will convert each input file given on the
command line to the corresponding C output file. If an input file
name does not have any extension, .pgc is
assumed. The file's extension will be replaced
by .c to construct the output file name.
But the output file name can be overridden using the
-o option.
If an input file name is just -,
ecpg reads the program from standard input
(and writes to standard output, unless that is overridden
with -o).
This reference page does not describe the embedded SQL language. See Chapter 35 for more information on that topic.
ecpg accepts the following command-line
arguments:
-c
Automatically generate certain C code from SQL code. Currently, this
works for EXEC SQL TYPE.
-C mode
Set a compatibility mode. mode can
be INFORMIX,
INFORMIX_SE, or ORACLE.
-D symbol
Define a C preprocessor symbol.
-h
Process header files. When this option is specified, the output file
extension becomes .h not .c,
and the default input file extension is .pgh
not .pgc. Also, the -c option is
forced on.
-iParse system include files as well.
-I directory
Specify an additional include path, used to find files included
via EXEC SQL INCLUDE. Defaults are
. (current directory),
/usr/local/include, the
PostgreSQL include directory which
is defined at compile time (default:
/usr/local/pgsql/include), and
/usr/include, in that order.
-o filename
Specifies that ecpg should write all
its output to the given filename.
Write -o - to send all output to standard output.
-r option
Selects run-time behavior. Option can be
one of the following:
no_indicatorDo not use indicators but instead use special values to represent null values. Historically there have been databases using this approach.
preparePrepare all statements before using them. Libecpg will keep a cache of prepared statements and reuse a statement if it gets executed again. If the cache runs full, libecpg will free the least used statement.
questionmarksAllow question mark as placeholder for compatibility reasons. This used to be the default long ago.
-t
Turn on autocommit of transactions. In this mode, each SQL command is
automatically committed unless it is inside an explicit
transaction block. In the default mode, commands are committed
only when EXEC SQL COMMIT is issued.
-vPrint additional information including the version and the "include" path.
--versionPrint the ecpg version and exit.
-?--helpShow help about ecpg command line arguments, and exit.
When compiling the preprocessed C code files, the compiler needs to
be able to find the ECPG header files in the
PostgreSQL include directory. Therefore, you might
have to use the -I option when invoking the compiler
(e.g., -I/usr/local/pgsql/include).
Programs using C code with embedded SQL have to be linked against
the libecpg library, for example using the
linker options -L/usr/local/pgsql/lib -lecpg.
The value of either of these directories that is appropriate for the installation can be found out using pg_config.
If you have an embedded SQL C source file named
prog1.pgc, you can create an executable
program using the following sequence of commands:
ecpg prog1.pgc cc -I/usr/local/pgsql/include -c prog1.c cc -o prog1 prog1.o -L/usr/local/pgsql/lib -lecpg