Cmd.exe bug with special characters

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xpdev
Posts: 2
Joined: 07 Feb 2021 12:27

Cmd.exe bug with special characters

#1 Post by xpdev » 07 Feb 2021 12:50

I have a batch file called

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`#'`#!^% ^%os%'&!&(.bat
with the following:

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@echo off
echo Test
echo %0
echo Test 2
If I escape the characters like this:

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set p=%
"`#'`#!^%p% ^%p%os%p%'&!&(.bat"
Then every command works.
But if I escape them like this:

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`#'`#!^^^%" "^^^%os^%'^&!^&^(.bat
Then only the first command works. The batch file exits after that. Why does this bug happen?

jfl
Posts: 170
Joined: 26 Oct 2012 06:40
Location: Saint Hilaire du Touvet, France
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Re: Cmd.exe bug with special characters

#2 Post by jfl » 09 Feb 2021 08:31

This is because %0 is the command string you typed, not the actual script name.
In the first case, it's quoted, so the special characters do not confuse the echo command.
In the second case, it's not quoted, and the special & and ( characters (which have lost their protecting ^ at this stage) do confuse it.

It would fail in both cases if you used %~0 instead of %0, thereby eliminating quotes in both cases.
Conversely, "%~0" would make it work in both cases.

jeb
Expert
Posts: 978
Joined: 30 Aug 2007 08:05
Location: Germany, Bochum

Re: Cmd.exe bug with special characters

#3 Post by jeb » 10 Feb 2021 10:19

Hi,

as JFL already said, the echo %0 is the problem.

If you want to see the content without problems, you could use the REM technique.

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@echo off
echo Test

echo on
REM # %0 #
@echo off

echo Test 2

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