ecpg

ecpg

1

Application

ecpg

embedded SQL C preprocessor

ecpg

option

file

Description {#app-ecpg-description}
===========

`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
[???](#ecpg) for more information on that topic.

Options
=======

`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.

`-i`

:   Parse 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_indicator`

    :   Do not use indicators but instead use special values to
        represent null values. Historically there have been databases
        using this approach.

    `prepare`

    :   Prepare 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.

    `questionmarks`

    :   Allow 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.

`-v`

:   Print additional information including the version and the
    \"include\" path.

`--version`

:   Print the ecpg version and exit.

`-?`; `--help`

:   Show help about ecpg command line arguments, and exit.

Notes
=====

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 [???](#app-pgconfig).

Examples
========

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
