section .data
        msg db 'Anus!', 0x0A
        file db 'anus_out'

section .text
        global _start

_start:
        ;; SYS_OPEN
        mov rax, 2    ; System call, sys_open
        mov rdi, file ; 1st arg, filename
        mov rsi, 1    ; 2nd arg, flag: O_WRONLY
        mov rdx, 0    ; 3rd arg, mode NULL
        syscall

        ;; Jump if failed
        cmp rax, 0
        jng _open_fail

        mov rbx, rax  ; Store the fd

        ;; SYS_WRITE
        mov rax, 1    ; System call, sys_write
        mov rdi, rbx  ; 1st arg, writing fd
        mov rsi, msg  ; 2nd arg, message
        mov rdx, 6    ; 3rd arg, length
        syscall

        ;; Jump if failed
        cmp rax, 0
        jng _write_fail

        ;; SYS_CLOSE
        mov rax, 3
        mov rdi, rbx
        syscall

        mov rdi, 0
        jmp _exit

_open_fail:
        mov rdi, -1
        jmp _exit

_write_fail:
        mov rdi, -2
        jmp _exit

_exit:
        mov rax, 60
        syscall