Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!shadooby!oxtrap!mudos!mju
From: mju@mudos.ann-arbor.mi.us (Marc Unangst)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Searching failure of COMMAND.COM
Message-ID: <663.252C039D@mudos.ann-arbor.mi.us>
Date: Thu, 05 Oct 89 21:35:11 EDT
Organization: FidoNet node 1:120/129 - Starship Enterprise, Ann Arbor MI

In article <2882NU013809@NDSUVM1>, NU013809@NDSUVM1.BITNET (Greg Wettstein) writes:
 >   argv[0] = "c::command.com"       <---- The name of the program to execute.
 >
 >   argv[1] = "-c"                   <---- The execute and return switch.
 >
 >   argv[2] = "dir"                  <---- Command to execute.
 >
 >   argv[3] = ""                     <---- Null to terminate arguement list.
 >
 >
 >When command.com was spawned with this arguement list an error was issued
 >repeatedly which said that an invalid search path was found.  Control then
 >returned to the daughter copy of command.com.  Typing an exit command would
 >return control back to MAKE.  Checking the environment revealed that the only
 >environment strings present were: PATH=  and COMSPEC=:command.com.

Well, I can see several problems...

1. COMSPEC should be a fully-qualified pathname.  ":command.com" isn't
even a legal one, so I'm very surprised that your machine hasn't crashed
with a "Can't load COMMAND.COM/System Halted." message yet.  You must
be lucky.  The correct COMSPEC would be "c:\command.com".

2. COMMAND.COM wants to have "/" in some versions of DOS; in others, it
likes the current switch character.  Use getswitchar() (if you use Turbo
C; if you're using MSC, you'll have to muck about with inline assembly)
to grab the current switch character, and use that.  UNDER NO CONDITIONS
should you hardcode "-c" in.  (Note: It might just be easier to have
a runtime environment variable or config-file option that specifies how
to execute a command.)

3. You should not hardcode in COMMAND.COM.  I'm sure there are a lot of
MKS people out there who swear up a storm every time a program that
has COMMAND.COM locked in comes down the pipe.  Please use COMSPEC or
a user-defined variable.

 >         setting.  I have heard conflicting reports on whether or not
 >         command.com checks the current switch character setting before
 >         parsing command lines passed to it.

That's because different versions of DOS work differently.  There are
some versions that have "/" coded in, others use switchar, and others
are just plain weird.

--  
Marc Unangst
Internet: mju@mudos.ann-arbor.mi.us
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