[Black Rose]

#define m_flNextAttack  83 // CBasePlayer, Linux +5

public plugin_init() {
    // ...
    register_forward(FM_CmdStart, "fwd_CmdStart");
    // ...
}

public fwd_CmdStart(id, uc_handle, seed) {
    
    // Add class check here.
    
    if ( ! is_user_alive(id) )
        return FMRES_IGNORED;
    
    if ( ! ( get_uc(uc_handle, UC_Buttons) & IN_DUCK ) )
        return FMRES_IGNORED;
    
    if ( get_user_weapon(id) == CSW_KNIFE ) // Perhaps?
        return FMRES_IGNORED;
    
    set_pdata_float(id, m_flNextAttack, 0.1, 5);
    
    return FMRES_HANDLED;
}