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Now that you have an idea how to form embedded SQL C programs, you probably want to know how to compile them. Before compiling you run the file through the embeddedSQLC preprocessor, which converts theSQL statements you used to special function calls. After compiling, you must link with a special library that contains the needed functions. These functions fetch information from the arguments, perform theSQL command using thelibpq interface, and put the result in the arguments specified for output.

The preprocessor program is calledecpg and is included in a normalPostgreSQL installation. Embedded SQL programs are typically named with an extension.pgc. If you have a program file calledprog1.pgc, you can preprocess it by simply calling:

ecpg prog1.pgc

This will create a file calledprog1.c. If your input files do not follow the suggested naming pattern, you can specify the output file explicitly using the-o option.

The preprocessed file can be compiled normally, for example:

cc -c prog1.c

The generated C source files include header files from thePostgreSQL installation, so if you installedPostgreSQL in a location that is not searched by default, you have to add an option such as-I/usr/local/pgsql/include to the compilation command line.

To link an embedded SQL program, you need to include thelibecpg library, like so:

cc -o myprog prog1.o prog2.o ... -lecpg

Again, you might have to add an option like-L/usr/local/pgsql/lib to that command line.

You can usepg_config orpkg-config with package namelibecpg to get the paths for your installation.

If you manage the build process of a larger project usingmake, it might be convenient to include the following implicit rule to your makefiles:

ECPG = ecpg%.c: %.pgc        $(ECPG) $<

The complete syntax of theecpg command is detailed inecpg.

Theecpg library is thread-safe by default. However, you might need to use some threading command-line options to compile your client code.