### 2.4 Building the source ¶

If you want to compile a source file that includes the `gss.h` header file, you must make sure that the compiler can find it in the directory hierarchy. This is accomplished by adding the path to the directory in which the header file is located to the compilers include file search path (via the `-I` option).

However, the path to the include file is determined at the time the source is configured. To solve this problem, GSS uses the external package `pkg-config` that knows the path to the include file and other configuration options. The options that need to be added to the compiler invocation at compile time are output by the `--cflags` option to `pkg-config gss`. The following example shows how it can be used at the command line:

    gcc -c foo.c `pkg-config gss --cflags`

Adding the output of ‘`pkg-config gss --cflags`’ to the compilers command line will ensure that the compiler can find the `gss.h` header file.

A similar problem occurs when linking the program with the library. Again, the compiler has to find the library files. For this to work, the path to the library files has to be added to the library search path (via the `-L` option). For this, the option `--libs` to `pkg-config gss` can be used. For convenience, this option also outputs all other options that are required to link the program with the GSS libarary (for instance, the ‘`-lshishi`’ option). The example shows how to link `foo.o` with GSS into a program `foo`.

    gcc -o foo foo.o `pkg-config gss --libs`

Of course you can also combine both examples to a single command by specifying both options to `pkg-config`:

    gcc -o foo foo.c `pkg-config gss --cflags --libs`