section .data
  err_msg: db "argument error", 0xa
  newline: db 0xa
  msg_size: equ 15

section .text
  global _start

_start:
  pop rax
  cmp rax, 2
  jne .arg_error

  ; write argument
  add rsp, 8
  pop rdi ; first argument

  mov r8, 0
  call .write

  jmp .exit

.write:
  inc rdi
  inc r8

  ; exit when rsi is 0
  cmp [rdi], byte 0
  jne .write

  sub rdi, r8

  ; output argument
  mov rax, 1
  mov rsi, rdi
  mov rdx, r8
  mov rdi, 1
  syscall

  mov rax, 1
  mov rsi, newline
  mov rdx, 1
  mov rdi, 1
  syscall

  ret

; output argument error message
.arg_error:
  ; write stdin
  mov rax, 1
  mov rsi, err_msg
  mov rdx, msg_size
  mov rdi, 1
  syscall

  ; exit status code 1
  mov rax, 60
  mov rdi, 1
  syscall
  ret

; exit function
.exit:
  mov rax, 60
  mov rdi, 0
  syscall
  ret