Nasm Linux - Print the contents of a file

pf.asm

SECTION .text    

global _start ; "global" means that the symbol can be accessed in other modules. In order to refer to a global symbol from another module, you must use the "extern" keyword
_start:
    mov rax, 2 ; syscall: open
    mov rdi, str_testFile
    mov rsi, 0 ; flags
    syscall

    mov rdi, rax ; the file descriptor
    mov rsi, buffer
    mov rdx, 128
    mov rax, 0; syscall: read
    syscall

    mov rdi, 1 ; stdout
    mov rsi, buffer
    mov rdx, rax ; the size returned by read
    mov rax, 1; syscall: write
    syscall

    mov rax, 60 ; syscal: exit
    mov rdi, 0 ; return code
    syscall

str_testFile: db "test.txt", 0

SECTION .data
buffer: TIMES 128 db 0