如何为修改JVM命令行的批处理脚本添加文件校验替换逻辑？

原脚本已实现：逐行读取源批处理文件，定位以java.exe开头且包含特定结尾子串的行，在结尾子串前插入config.ini中定义的JVM开关后生成新文件，未匹配行原样输出。现需新增校验逻辑，仅满足以下两个条件时，才用新文件替换源文件：

• 新文件大小等于源文件大小加上插入字符的总长度
• 源文件与新文件的大小差异占比极小（可自定义阈值）

修改后的完整脚本 #

@echo off

setlocal enabledelayedexpansion
set sourcefile=my_source_script.bat
set "newfile=new_%sourcefile%"
:: 定义差异占比阈值（0.001代表0.1%）
set "size_diff_threshold=0.001"
set modify_count=0

:: Create the destination file
type NUL > "%newfile%"

:: Define the part to be inserted in the JVM Command Line
:: The switches to be inserted are defined in config.ini file
call :load_config
echo insert switches value = %INSET_JVM_SWITCHES%

:: 计算单次插入的字符长度（包含空格）
set "insert_len=0"
if defined INSET_JVM_SWITCHES (
    set "insert_str=!INSET_JVM_SWITCHES! "
    :: 用临时文件计算字符串长度
    echo(!insert_str!>tmp_len.tmp
    for %%f in (tmp_len.tmp) do set insert_len=%%~zf
    del tmp_len.tmp
    :: 减去Windows换行符的2字节（CR+LF）
    set /a insert_len-=2
)

REM Define the first and last part which will be used to identify the lines to be modified in the batch script
set "firstpart=java.exe"
set "lastpart=com.main.java.class.of.the.application -auto"
REM Read source line by line and prefix with line number to pick empty lines
FOR /f "delims=" %%l IN ('findstr /N "^" ".\%sourcefile%"') DO (
  set "line=%%l"
  REM Remove the line number until the column
  set "line=!line:*:=!"
  REM Initialize left and right parts. This is needed to identify the lines to be modified
  set "left=x"
  if not "!line!"=="" for %%b in ("!lastpart!") do set "left=x!line:%%~b=!"
  if not "!line!"=="" for %%b in ("!firstpart!") do set "left=x!line:%%~b=!"
  set "right=x!line!"
  REM If firstpart and lastpart are found in line ...
  if not "!line!"=="" if not !left!==!right! (
    REM Update the line by replacing the last part with the addition plus the last part
    for %%b in ("!lastpart!") do set "line=!line:%%~b=!INSET_JVM_SWITCHES! %%~b!"
    set /a modify_count+=1
  )
  REM Write the line to the new batch script
  echo(!line!>>"%newfile%"
)

:: 开始执行校验与替换逻辑
echo.
echo --- 开始校验文件 ---
:: 获取源文件和新文件大小
for %%f in ("%sourcefile%") do set "source_size=%%~zf"
for %%f in ("%newfile%") do set "new_size=%%~zf"

echo 源文件大小: %source_size% 字节
echo 新文件大小: %new_size% 字节
echo 修改行数: %modify_count%
echo 单次插入长度: %insert_len% 字节

:: 计算预期新增总长度
set /a expected_add=modify_count * insert_len
echo 预期新增长度: %expected_add% 字节

:: 校验条件1：新文件大小等于源文件大小+预期新增长度
set condition1=0
if %new_size% equ %source_size% (
    if %expected_add% equ 0 set condition1=1
) else (
    set /a calc_size=source_size + expected_add
    if %new_size% equ %calc_size% set condition1=1
)

:: 校验条件2：差异占比小于阈值（避免源文件为0的极端情况）
set condition2=0
if %source_size% gtr 0 (
    :: 计算差异值（取绝对值）
    set /a diff= new_size - source_size
    if !diff! lss 0 set /a diff= -diff
    :: 用powershell完成浮点计算差异占比
    for /f %%r in ('powershell "!diff! / !source_size!"') do set "diff_ratio=%%r"
    :: 比较占比与阈值
    for /f %%r in ('powershell "!diff_ratio! -lt !size_diff_threshold!"') do set condition2=%%r
) else (
    :: 源文件为空时，只有新文件也为空才通过
    if %new_size% equ 0 set condition2=1
)

echo.
echo 条件1（大小匹配预期）: %condition1%
echo 条件2（差异占比极小）: %condition2%

:: 满足两个条件则执行替换
if %condition1% equ 1 if %condition2% equ 1 (
    echo 校验通过，执行替换...
    del "%sourcefile%"
    ren "%newfile%" "%sourcefile%"
    echo 替换完成
) else (
    echo 校验不通过，保留原文件与新文件
)

goto :eof

::**************************************************************************************
:: Function: Load Config
:: Purpose: Parse the text file config.ini
:load_config
echo.
echo Loading config data from config.ini file ...
echo.
SET "configfile=config.ini"
if not exist %configfile% (
    echo Error: The following config file was not found:
    echo    %configfile%
    exit /b 1
)
set "uniqueList="
:: remove variables starting count_
FOR  /F "delims==" %%e In ('set count_ 2^>Nul') DO SET "%%e="

FOR /f "usebackq tokens=1* delims==" %%b IN ("%configfile%") DO (
 IF "%%c" neq "" (
  set keyname=%%b
  IF DEFINED count_!keyname! (SET /a count_%%b+=1) ELSE (SET /a count_!keyname!=0 & set uniqueList=!uniqueList!,!keyname!)
  if "!keyname:~-4!"=="_arr" (
    SET "!keyname![!count_%%b!]=%%c"
  ) else (
    SET "!keyname!=%%c"
  )
 )
)
:: Remove first char if it is a coma ,
if "!uniqueList!" neq "" if "!uniqueList:~0,1!" equ "," set uniqueList=!uniqueList:~1!
echo Completed parsing the config file.
echo.
goto :eof
::****************************************************************

关键逻辑说明 #

1. 统计修改行数：在匹配到需要插入JVM开关的行时，通过modify_count变量累计修改次数
2. 计算插入长度：将插入字符串写入临时文件，通过文件大小获取字符串长度（减去Windows换行符的2字节）
3. 文件大小校验：
   • 计算预期新增总长度：修改次数 × 单次插入长度
   • 对比新文件实际大小与源文件大小+预期新增长度是否一致
4. 差异占比校验：借助PowerShell完成浮点计算，判断大小差异占源文件的比例是否小于设定阈值（默认0.1%）
5. 替换操作：仅当两个条件都满足时，删除源文件并将新文件重命名为源文件名

内容的提问来源于stack exchange，提问作者tarekahf