In original article you need to specify the function address manually. I made it detect the function address automatically.

hello.c

#include <stdio.h>
#include <unistd.h>

void
f (int n)
{
  printf ("Number: %d\n", n);
}

int
main (int argc,
      char * argv[])
{
  int i = 0;

  while (1)
  {
    f (i++);
    sleep (1);
  }
}

inector.py

# from https://frida.re/docs/installation/
import frida

session = frida.attach("hello")

script = session.create_script("""
// Find the module for the program itself, always at index 0:
const m = Process.enumerateModules()[0];

rpc.exports.enumerateModules = function () {
  return Process.enumerateModules()[0].enumerateSymbols();
};
""")
script.load()

data = script.exports.enumerate_modules()
function_f = [x for x in data if x['name']=='f'][0]
function_f_address = function_f['address']

script = session.create_script("""
// Find the module for the program itself, always at index 0:
const m = Process.enumerateModules()[0];

Interceptor.attach(ptr("%s"), {
    onEnter: function(args) {
        send(args[0].toInt32());
    }
});
""" % int(function_f_address, 16))

def on_message(message, data):
    print(message)

script.on('message', on_message)
script.load()

input()