[文本处理] 变量名尾部为若干等号的 set 命令及变量扩展问题

neorobin

在 WIN7 64 位下

1.

set _==5
echo %_=%
set /a %_=% + 3
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输出

5
8
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2.

set _==5
echo %_%
echo %_=%
set /a %_=% + 3
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输出

=5
%_=%
Missing operand.
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3.

set _==5
echo %_=%
echo %_%
set /a %_=% + 3
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输出

5
%_%
8
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以下代码做了一些测试:

当变量名尾部为若干个等号时, 例如:
$=====
_========
能否用 set 命令对这样的变量成功赋值? 如果成功赋值, 那么可以用怎样的形式做变量扩展

当在 WIN XP 32bit 下测试时, 未能对这样的变量成功赋值;

但当在 WIN7 64bit 下测试时, 某些形式 可以扩展, 但另一些形式却未成成功 扩展, 而其中的规律暂不明.

当以下划线 _ 为变量名首字符时, 尾部等号的个数为 1, 2, 5, 6, 10, 11, 14, 17, 20 以及超过 20 个时, 可成功扩展.

而当变量名首字符为 $ 时,  尾部等号的个数达到 20 以及超过 20 个时, 可成功扩展, 当首字符换成: @  #  ; 时, 也得到这样的结果

测试代码:

@echo off & mode 160, 1000

set _====================================================================================================VAL
set $====================================================================================================VAL
set #====================================================================================================VAL
set @====================================================================================================VAL
set ;====================================================================================================VAL

REM will report: The syntax of the command is incorrect.
set =====================================================================================================VAL

echo _ is [%_%]
echo _= is [%_=%]
echo _== is [%_==%]
echo _=== is [%_===%]
echo _==== is [%_====%]
echo _===== is [%_=====%]
echo _====== is [%_======%]
echo _======= is [%_=======%]
echo _======== is [%_========%]
echo _========= is [%_=========%]
echo _========== is [%_==========%]
echo _=========== is [%_===========%]
echo _============ is [%_============%]
echo _============= is [%_=============%]
echo _============== is [%_==============%]
echo _=============== is [%_===============%]
echo _================ is [%_================%]
echo _================= is [%_=================%]
echo _================== is [%_==================%]
echo _=================== is [%_===================%]
echo _==================== is [%_====================%]
echo _===================== is [%_=====================%]
echo _====================== is [%_======================%]
echo _======================= is [%_=======================%]
echo _======================== is [%_========================%]
echo _========================= is [%_=========================%]
echo _========================== is [%_==========================%]
echo _=========================== is [%_===========================%]
echo _============================ is [%_============================%]
echo _============================= is [%_=============================%]
echo _============================== is [%_==============================%]
echo _=============================== is [%_===============================%]
echo _================================ is [%_================================%]
echo _================================= is [%_=================================%]
echo _================================== is [%_==================================%]
echo _=================================== is [%_===================================%]
echo _==================================== is [%_====================================%]
echo _===================================== is [%_=====================================%]

pause

echo $ is [%$%]
echo $= is [%$=%]
echo $== is [%$==%]
echo $=== is [%$===%]
echo $==== is [%$====%]
echo $===== is [%$=====%]
echo $====== is [%$======%]
echo $======= is [%$=======%]
echo $======== is [%$========%]
echo $========= is [%$=========%]
echo $========== is [%$==========%]
echo $=========== is [%$===========%]
echo $============ is [%$============%]
echo $============= is [%$=============%]
echo $============== is [%$==============%]
echo $=============== is [%$===============%]
echo $================ is [%$================%]
echo $================= is [%$=================%]
echo $================== is [%$==================%]
echo $=================== is [%$===================%]
echo $==================== is [%$====================%]
echo $===================== is [%$=====================%]
echo $====================== is [%$======================%]
echo $======================= is [%$=======================%]
echo $======================== is [%$========================%]
echo $========================= is [%$=========================%]
echo $========================== is [%$==========================%]
echo $=========================== is [%$===========================%]
echo $============================ is [%$============================%]
echo $============================= is [%$=============================%]
echo $============================== is [%$==============================%]
echo $=============================== is [%$===============================%]
echo $================================ is [%$================================%]
echo $================================= is [%$=================================%]
echo $================================== is [%$==================================%]
echo $=================================== is [%$===================================%]
echo $==================================== is [%$====================================%]
echo $===================================== is [%$=====================================%]

pause
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输出结果

The syntax of the command is incorrect.
_ is [===================================================================================================VAL]
_= is [==================================================================================================VAL]
_== is [=================================================================================================VAL]
_=== is []
_==== is []
_===== is [==============================================================================================VAL]
_====== is [=============================================================================================VAL]
_======= is []
_======== is []
_========= is []
_========== is [=========================================================================================VAL]
_=========== is [========================================================================================VAL]
_============ is []
_============= is []
_============== is [=====================================================================================VAL]
_=============== is []
_================ is []
_================= is [==================================================================================VAL]
_================== is []
_=================== is []
_==================== is [===============================================================================VAL]
_===================== is [==============================================================================VAL]
_====================== is [=============================================================================VAL]
_======================= is [============================================================================VAL]
_======================== is [===========================================================================VAL]
_========================= is [==========================================================================VAL]
_========================== is [=========================================================================VAL]
_=========================== is [========================================================================VAL]
_============================ is [=======================================================================VAL]
_============================= is [======================================================================VAL]
_============================== is [=====================================================================VAL]
_=============================== is [====================================================================VAL]
_================================ is [===================================================================VAL]
_================================= is [==================================================================VAL]
_================================== is [=================================================================VAL]
_=================================== is [================================================================VAL]
_==================================== is [===============================================================VAL]
_===================================== is [==============================================================VAL]
Press any key to continue . . .
$ is [===================================================================================================VAL]
$= is []
$== is []
$=== is []
$==== is []
$===== is []
$====== is []
$======= is []
$======== is []
$========= is []
$========== is []
$=========== is []
$============ is []
$============= is []
$============== is []
$=============== is []
$================ is []
$================= is []
$================== is []
$=================== is []
$==================== is [===============================================================================VAL]
$===================== is [==============================================================================VAL]
$====================== is [=============================================================================VAL]
$======================= is [============================================================================VAL]
$======================== is [===========================================================================VAL]
$========================= is [==========================================================================VAL]
$========================== is [=========================================================================VAL]
$=========================== is [========================================================================VAL]
$============================ is [=======================================================================VAL]
$============================= is [======================================================================VAL]
$============================== is [=====================================================================VAL]
$=============================== is [====================================================================VAL]
$================================ is [===================================================================VAL]
$================================= is [==================================================================VAL]
$================================== is [=================================================================VAL]
$=================================== is [================================================================VAL]
$==================================== is [===============================================================VAL]
$===================================== is [==============================================================VAL]
Press any key to continue . . .
复制代码

CrLf

碰到过这类问题，测试角度不一样，但同样摸不着头脑...

Linuxer

1、2、3勉强还能看一下。。。再往下，，，，已经晕了。

CrLf

我的测试是这样的：

set a=b=c=d

echo %a%
echo %a=b%
echo %a=b=c%
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Linuxer

回复 4# CrLf

echo %a=b=c
复制代码

楼上的，你%掉了。

neorobin

这个想更深入点了解, 我想得用 反编译 和 内存分析 工具, 是很伤脑筋的工作吧.

我现在只能停留在知道有这个现象存在了, 不小心扎到手时, 就会记起来这里确实有个钉子的.

CrLf

回复 5# Linuxer


    为什么 % 看起来这么像肥皂

回复 6# neorobin


    明天用 od 试着跟一下...

ezaohaha

回复 7# CrLf
不会汇编  55555～～～正在看  买到了 王爽的教材  确实很通俗易懂