Re: Patch for missing shell commands in rc2

[J. David Bryan]

On 22 Mar 2006 at 6:40, Eli Zaretskii wrote:

> My example is with the following command:
> 
>    start c:/foo/bar/baz.exe
> 
> Do you see the issue now?

I'm afraid not, because the above works fine in Win95 and Win98, e.g.  Try:

  start c:/windows/notepad.exe

...under command.com, and I believe that you'll see that notepad starts as 
expected.

I recognize that trying to do "c:/windows/notepad.exe" directly from the 
shell doesn't work and that "c:\windows\notepad.exe" is required instead, 
but the problem there doesn't pertain to internal commands, which are 
started without paths (we don't do "c:/windows/start" if "start" is an 
internal command).


> > Are you thinking that someone using command.com might have
> > a makefile that invokes a command with the same name as a
> > cmd.exe internal command, is currently passing forward-slashed
> > filenames to it, which it accepts, whereas if the same parameters
> > were passed via a batch file invocation, it wouldn't?
> 
> Yes, see above.

After considering my example more, I'm not sure that pertains either.  
Command.com doesn't appear to alter the parameters passed to an external 
command, so if that command accepted forward-slashed parameters before, it 
should still work with forward-slashed parameters even if it's started via 
the shell.  Command.com seems to object only when forward slashes in 
filenames are passed to internal commands, where the slashes are confused 
with command switches.

Also, you had written earlier:

> Another problem is the 126-character limit on COMMAND.COM's command
> line; invoking programs directly via CreateProcess won't hit this
> limit. 

MSDN says that the limit for batch command lines, i.e., how make runs shell 
commands, is 1024 characters under command.com:

  http://msdn.microsoft.com/archive/en-us/win9x/msdos_694j.asp

So I believe that the only incompatibility my original patch would cause 
would be to existing makefiles running under command.com that had issued 
command lines longer than 1024 characters to programs whose names conflict 
with the added cmd.exe shell command names.  Counterexamples welcomed, 
though.

If you believe that limitation is too restrictive, however, I'm willing to 
undertake the selection of sh_cmds_dos at run time.  That would appear to 
add some overhead to every command execution, though.


> Feel free to ask for advice. 

Your offer is appreciated.


> I cannot imagine you really need to invoke a command via "start" in a
> Makefile.  If that's a real example, can you describe it in mode
> detail? 

I have three situations that use "start" in the makefile as a convenience:

 * image processing -- the makefile runs a series of programs on image
   files and then starts a viewer or editor on the result

 * pdf generation -- the makefile compiles a pdf from a series of image
   files and then starts Acrobat Reader to view the result

 * program debugging -- the makefile compiles a program and then starts gdb
   on the executable.

In all cases, I can run the last step manually, e.g., run the image editor, 
do File | Open, navigate to the processed file, and load it.  Much nicer to 
have the makefile do that automatically, though.

                                      -- Dave