Can you show me some examples of using Ruby with C APIs?

Can you show me some examples of using Ruby with C APIs?

Sure! One common example is using the Ruby C API to create a simple Ruby extension. Would you like to see a specific example?

Yes, please show me how to create a basic Ruby extension.

To create a basic Ruby extension, you need to write a C function and then use the Ruby C API to expose it. Here's a simple example:

#include <ruby.h>

VALUE method_hello(VALUE self) {
    return rb_str_new_cstr("Hello from C!");
}

void Init_my_extension() {
    rb_define_method(rb_cObject, "hello", method_hello, 0);
}

This code defines a method hello that returns a string. You can compile this into a Ruby extension.

How do I compile this C code into a Ruby extension?

You can compile the C code using the following command:

gcc -shared -o my_extension.so my_extension.c -I$(ruby -e 'puts RbConfig::CONFIG["includedir"]') -I$(ruby -e 'puts RbConfig::CONFIG["archdir"]') -L$(ruby -e 'puts RbConfig::CONFIG["libdir"]') -lruby

Make sure to replace my_extension.c with the name of your C file.

What do I do after compiling the extension?

After compiling, you can load the extension in your Ruby code using require './my_extension' and then call the hello method like this:

require './my_extension'
puts hello()  # This will output: Hello from C!