How to get arguments from argc/argv

[XuJiandong]

It's sometime required to get the arguments from argc/argv. Here is the code snippet for this task:

ckb_std::entry!(program_entry);

fn program_entry(argc: u64, argv: *const *const u8) -> i8 {
    let first_arg = if argc > 0 {
        let args = unsafe { from_raw_parts(argv, argc as usize) };
        let s = unsafe { CStr::from_ptr(args[0]) };
        Some(s.to_str().unwrap())
    } else {
        None
    };

The code above shows how to get the first argument.