NAME
	Execute -- Execute a CLI command

    SYNOPSIS
	success = Execute( commandString, input, output )
	D0		   D1		  D2	 D3

	BOOL Execute(STRPTR, BPTR, BPTR)

    FUNCTION
	This function attempts to execute the string commandString as a
	Shell command and arguments. The string can contain any valid input
	that you could type directly in a Shell, including input and output
	redirection using < and >.  Note that Execute() doesn't return until
	the command(s) in commandstring have returned.

	The input file handle will normally be zero, and in this case
	Execute() will perform whatever was requested in the commandString
	and then return. If the input file handle is nonzero then after the
	(possibly empty) commandString is performed subsequent input is read
	from the specified input file handle until end of that file is
	reached.

	In most cases the output file handle must be provided, and is used
	by the Shell commands as their output stream unless output
	redirection was specified. If the output file handle is set to zero
	then the current window, normally specified as *, is used. Note
	that programs running under the Workbench do not normally have a
	current window.

	Execute() may also be used to create a new interactive Shell process
	just like those created with the NewShell command. In order to do
	this you would call Execute() with an empty commandString, and pass
	a file handle relating to a new window as the input file handle.
	The output file handle would be set to zero. The Shell will read
	commands from the new window, and will use the same window for
	output. This new Shell window can only be terminated by using the
	EndCLI command.

	Under V37, if an input filehandle is passed, and it's either
	interactive or a NIL: filehandle, the pr_ConsoleTask of the new
	process will be set to that filehandle's process (the same applies
	to SystemTagList()).

	For this command to work the program Run must be present in C: in
	versions before V36 (except that in 1.3.2 and any later 1.3 versions,
	the system first checks the resident list for Run).

    INPUTS
	commandString - pointer to a null-terminated string
	input	      - BCPL pointer to a file handle
	output	      - BCPL pointer to a file handle

    RESULTS
	success - BOOLEAN indicating whether Execute was successful
		  in finding and starting the specified program.  Note this
		  is NOT the return code of the command(s).
    SEE ALSO
	SystemTagList(), NewShell, EndCLI, Run