Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!ukma!simon
From: simon@ms.uky.edu (Simon Gales)
Newsgroups: comp.binaries.ibm.pc.d
Subject: Re: BEWARE of changing the command line switch (switchar)
Keywords: switchar COMMAND.COM
Message-ID: <10434@s.ms.uky.edu>
Date: 26 Oct 88 00:41:18 GMT
References: <824@kksys.UUCP> <170@ocsmd.OCS.COM> <826@kksys.UUCP>
Reply-To: simon@ms.uky.edu (Simon Gales)
Distribution: na
Organization: U of Kentucky, Mathematical Sciences
Lines: 31

The reason programs have problems with altered switch characters is not
really complicated.  When an internal DOS command is invoked from within
the program (like 'dir'), the program spawns off a copy of command.com
and makes it perform the command ('dir'). 

In MS C:

	system("command.com /c dir");

	This is supposed to run a command.com and make it do a dir.
	The normal switchar is '/' so the programmer naturally used '/'
	to access the '/c' option of command.com.

	When the above 'system(" ... ")' is done with the switch char
	changed, command.com does not understand the '/c' anymore, so 
	it returns an error instead of performing the command.

The same happens in many other languages, since the string passed to 
DOS ("command.com /c dir") is usually just typed in directly; rather 
than going to the trouble of finding out the current switch character
and building the string correctly.

It may be possible to edit the .exe/.com file, find these strings and
change the '/' to a '-' or whatever.  I've never tried this, but Norton
utilities would probably make it easy.

-- 
<-------------------------------------------------------------------------->
<---   Simon Gales@University of Ky                 254-9387/257-3597   --->
<---            [ simon@ms.uky.edu ]  |  [ simon@UKMA.BITNET ]          --->
<-------------------------------------------------------------------------->