Display min_length

[eluser]ameur[/eluser]
Hello,
Please i want to display the value of min_length in my costum message because i've use it in two times (field username and field password)
this is my code:

Code:

$this->load->library('form_validation');
                
                $this->form_validation->set_rules('username', 'Identifiant', 'trim|required|min_length[3]|alpha_numeric|xss_clean|callback__valid_username');
                $this->form_validation->set_rules('pwd', 'Mot de passe', 'trim|required|min_length[5]|md5');
                $this->form_validation->set_rules('email', 'Email', 'trim|valid_email');
                
                
                $this->form_validation->set_message('required', '» champ obligatoire');
                $this->form_validation->set_message('min_length', '» ce champ doit contenir au moins /*something missing here!!!*/ caracteres');
                $this->form_validation->set_message('_valid_username', '» cet identifiant est déja utilise');
                $this->form_validation->set_message('valid_email', '» email invalide');
                
                $this->form_validation->set_error_delimiters('<span class="single_error">', '</span>');

thank you