Writing to a file in nasm using system calls

As part of an assignment, I'm supposed to write to a file using system calls. Everything works fine except when I try to open the file in gedit (Linux). It says it can't identify the character encoding. Notepad (on Windows) opens the file just fine.

Why doesn't this work on Linux?

Here's the code:

    section .text

    global _start

        _start:
                    mov EAX, 8
                    mov EBX, filename
                    mov ECX, 0700
                    int 0x80
                    mov EBX, EAX
                    mov EAX, 4
                    mov ECX, text
                    mov EDX, textlen
                    int 0x80
                    mov EAX, 6
                    int 0x80
                    mov eax, 1
                    int 0x80
        
    section .data

        filename db "./output.txt", 0
        text db "hello world", 0
        textlen equ $ - text

Adding a linefeed character after the output string fixed it.