What does this Assembly snippet output?

1.global _main
2.align 2
3_main:
4    stp x29, x30, [sp, #-32]!
5    adrp x8, str@PAGE
6    add x8, x8, str@PAGEOFF
7    mov w9, #0
8len_loop:
9    ldrb w10, [x8], #1
10    cbz w10, len_done
11    add w9, w9, #1
12    b len_loop
13len_done:
14    sub sp, sp, #16
15    str x9, [sp]
16    adrp x0, fmt@PAGE
17    add x0, x0, fmt@PAGEOFF
18    bl _printf
19    add sp, sp, #16
20    ldp x29, x30, [sp], #32
21    mov w0, #0
22    ret
23.section __TEXT,__cstring
24str: .asciz "hello"
25fmt: .asciz "%d\n"