汇编SCAS指令

section .text
   global _start        ;must be declared for using gcc

_start:                    ;tell linker entry point

   mov ecx,len
   mov edi,my_string
   mov al , 'e'
   cld
   repne scasb
   je found ; when found
   ; If not not then the following code

   mov eax,4
   mov ebx,1
   mov ecx,msg_notfound
   mov edx,len_notfound
   int 80h
   jmp exit

found:
   mov eax,4
   mov ebx,1
   mov ecx,msg_found
   mov edx,len_found
   int 80h

exit:
   mov eax,1
   mov ebx,0
   int 80h

section .data
my_string db 'hello world', 0
len equ $-my_string  

msg_found db 'found!', 0xa
len_found equ $-msg_found

msg_notfound db 'not found!'
len_notfound equ $-msg_notfound