在程序集中的文本文件末尾追加

Question

我在這裏有一個TASM代碼，並且在我再次運行程序時它不會追加新的字符串。我想感謝us2012幫助我達到這個「國家」。

; This example program creates a file and then writes to it. 
.model small 
.stack 

.data 
CR equ 13 
LF equ 10 

StartMessage DB "This program creates a file called NEW.TXT" 
     DB ,"on the C drive.$" 

EndMessage DB CR,LF,"File create OK, look at file to" 
     DB ,"be sure.$" 

WriteMessage DB "An error has occurred (WRITING)$" 
OpenMessage DB "An error has occurred (OPENING)$" 
CreateMessage DB "An error has occurred (CREATING)$" 

WriteMe DB "HELLO, THIS IS A TEST, HAS IT WORKED?",0 
FileName DB "new.txt",0 ; name of file to open 
Handle DW ? ; to store file handle 

.code 
START: 
mov ax,@data ; base address of data segment 
mov ds,ax ; put it in ds 
mov dx,offset StartMessage 
mov ah,09h 
int 21h 

mov si,offset FileName ; put offset of filename in dx 
xor cx,cx  ; clear cx - make ordinary file 
mov ah,6Ch  ; function 3Ch - create a file 
mov al, 0 
int 21h   ; call DOS service 
mov bx, Handle 
xor cx, cx 
xor dx, dx 
mov ah, 42h 
mov al, 02h 
int 21h 


jc CreateError  ; jump if there is an error 



mov si,offset FileName ; put offset of filename in dx 
mov al,2  ; access mode -read and write 
mov ah,3Dh  ; function 3Dh - open the file 
int 21h   ; call dos service 



jc OpenError  ; jump if there is an error 



mov Handle,ax  ; save value of handle 
mov bx, Handle 
xor cx, cx 
xor dx, dx 
mov ah, 42h 
mov al, 02h 
int 21h 



mov dx,offset WriteMe ; address of information to write 
mov bx,Handle  ; file handle for file 
mov cx,38  ; 38 bytes to be written 
mov ah,40h  ; function 40h - write to file 
int 21h   ; call dos service 

jc WriteError  ; jump if there is an error 
cmp ax,cx  ; was all the data written? 
jne WriteError  ; no it wasn't - error! 

mov bx,Handle  ; put file handle in bx 
mov ah,3Eh  ; function 3Eh - close a file 
int 21h   ; call dos service 

mov dx,offset EndMessage 
mov ah,09h 
int 21h 

ReturnToDOS: 

mov ax,4C00h  ; terminate program 
int 21h 

WriteError: 
mov dx,offset WriteMessage 
jmp EndError 

OpenError: 
mov dx,offset OpenMessage 
jmp EndError 

CreateError: 
mov dx,offset CreateMessage 

EndError: 
mov ah,09h 
int 21h 
mov ax,4C01h 
int 21h 

END START 

如果我使用3Ch，該程序的作品，但它不附加到文件末尾。通過使用6Ch代替3Ch，this說，它不會截斷現有的文件，以零個字節，但每當我運行的代碼，在那裏創建該文件是一個錯誤（沒有文件被創建）。請幫我修復代碼。非常感謝你！

編輯2：

; This example program creates a file and then writes to it. 
.model small 
.stack 

.data 
CR equ 13 
LF equ 10 

StartMessage DB "This program creates a file called NEW.TXT" 
     DB ,"on the C drive.$" 

EndMessage DB CR,LF,"File create OK, look at file to" 
     DB ,"be sure.$" 

WriteMessage DB "An error has occurred (WRITING)$" 
OpenMessage DB "An error has occurred (OPENING)$" 
CreateMessage DB "An error has occurred (CREATING)$" 

WriteMe DB "HELLO, THIS IS A TEST, HAS IT WORKED?",0 
FileName DB "new3.txt",0 ; name of file to open 
Handle DW ? ; to store file handle 

.code 
START: 
mov ax,@data ; base address of data segment 
mov ds,ax ; put it in ds 
mov dx,offset StartMessage 
mov ah,09h 
int 21h 

mov si, offset FileName  ; put offset of filename in dx 
xor cx,cx  ; clear cx - make ordinary file 
mov ah,6Ch  ; function 3Ch - create a file 
mov bx, 3 
mov dx, 12h 
int 21h   ; call DOS service 

jc CreateError  ; jump if there is an error 

mov ah,3Eh  ; function 3Eh - close a file 
int 21h   ; call dos service 


mov dx, offset FileName  ; put offset of filename in dx 
mov al,2  ; access mode -read and write 
mov ah,3Dh  ; function 3Dh - open the file 
int 21h   ; call dos service 

jc OpenError  ; jump if there is an error 

mov Handle,ax  ; save value of handle 
mov bx, Handle 
xor cx, cx 
xor dx, dx 
mov ah, 42h 
mov al, 02h 
int 21h 

mov dx,offset WriteMe ; address of information to write 
mov bx,Handle  ; file handle for file 
mov cx,38  ; 38 bytes to be written 
mov ah,40h  ; function 40h - write to file 
int 21h   ; call dos service 

jc WriteError  ; jump if there is an error 
cmp ax,cx  ; was all the data written? 
jne WriteError  ; no it wasn't - error! 

mov bx,Handle  ; put file handle in bx 
mov ah,3Eh  ; function 3Eh - close a file 
int 21h   ; call dos service 

mov dx,offset EndMessage 
mov ah,09h 
int 21h 

ReturnToDOS: 

mov ax,4C00h  ; terminate program 
int 21h 

WriteError: 
mov dx,offset WriteMessage 
jmp EndError 

OpenError: 
mov dx,offset OpenMessage 
jmp EndError 

CreateError: 
mov dx,offset CreateMessage 

EndError: 
mov ah,09h 
int 21h 
mov ax,4C01h 
int 21h 

END START 

Answer 1

看這部分：

mov dx,offset FileName ; put offset of filename in dx 
xor cx,cx  ; clear cx - make ordinary file 
mov ah,6Ch  ; function 3Ch - create a file 
mov al, 0 
int 21h   ; call DOS service 

和在the relevant documentation：

AX = 6C00h 
BL = open mode as in AL for normal open (see also AH=3Dh) 
... 
BH = flags 
... 
CX = create attribute (see #01769). 
DL = action if file exists/does not exist (see #01770). 
DH = 00h (reserved). 
DS:SI -> ASCIZ file name 

Return: 
CF set on error AX = error code (see #01680 at AH=59h/BX=0000h) 
CF clear if successful AX = file handle 
CX = status (see #01768) 

函數需要一個si d不是dx有文件名的偏移量。

你不設置bx。

你不設置dx。

您不檢查錯誤。

您不保存文件句柄。

看這個部分：

mov bx, Handle 
xor cx, cx 
xor dx, dx 
mov ah, 42h 
mov al, 02h 
int 21h 

Handle在這一點上未初始化，因爲你永遠不會保存手柄扳到這個變量。

現在，這裏：

mov dx,offset FileName ; put offset of filename in dx 
mov al,2  ; access mode -read and write 
mov ah,3Dh  ; function 3Dh - open the file 
int 21h   ; call dos service 

你試圖再次打開打開的文件。您需要在開封前關閉它。或者，如果你有句柄，只要繼續處理文件，不要關閉並重新打開它。