Print Page - Easily write lines to a text file

Title: Easily write lines to a text file
Post by: Vortex on October 25, 2026, 06:38:33 PM

Hello,

Simple functions to write lines to a text file :

.386
.model flat,stdcall
option casemap:none

GENERIC_WRITE equ 40000000h
CREATE_ALWAYS equ 2

CreateFileA PROTO :DWORD,:DWORD,:DWORD,:DWORD,:DWORD,:DWORD,:DWORD
CreateFile equ <CreateFileA>

.code

OpenFileToWrite PROC fname:DWORD

    invoke  CreateFile,fname,GENERIC_WRITE,\
            0,0,CREATE_ALWAYS,0,0
    ret

OpenFileToWrite ENDP

END

Code Select

.386
.model flat,stdcall
option casemap:none

lstrlenA PROTO :DWORD
lstrlen EQU <lstrlenA>

WriteFile PROTO :DWORD,:DWORD,:DWORD,:DWORD,:DWORD

.code

WriteLine PROC hFile:DWORD,LineAddr:DWORD

LOCAL BytesWritten:DWORD

    invoke  lstrlen,LineAddr
    lea     edx,BytesWritten
    invoke  WriteFile,hFile,LineAddr,eax,edx,0
    ret

WriteLine ENDP

END

A quick example :

Code Select

.386
.model flat,stdcall
option casemap:none

CloseHandle PROTO :DWORD
ExitProcess PROTO :DWORD

OpenFileToWrite PROTO :DWORD
WriteLine PROTO :DWORD,:DWORD

.data

fname   db 'Test.txt',0
line1   db 'This is a test.',13,10,0
line2   db 'Another test.',0

.data?

hFile   dd ?

.code

start:

    invoke  OpenFileToWrite,ADDR fname
    mov     hFile,eax

    invoke  WriteLine,eax,ADDR line1
    invoke  WriteLine,hFile,ADDR line2

    invoke  CloseHandle,hFile

    invoke  ExitProcess,0

END start

Title: Re: Easily write lines to a text file
Post by: TimoVJL on October 25, 2026, 07:49:09 PM

Those support functions are also useful for x64, when parameter count is less that five.

Title: Re: Easily write lines to a text file
Post by: Vortex on October 25, 2026, 08:52:42 PM

Hi Timo,

Attached is the 64-bit version of the functions.

Pelles C forum

Assembly language => Assembly discussions => Topic started by: Vortex on October 25, 2026, 06:38:33 PM