NAME
        RunCommand -- Runs a program using the current process (V36)

   SYNOPSIS
        rc = RunCommand(seglist, stacksize, argptr, argsize)
        D0                D1         D2       D3      D4

        long runcommand(bptr, ulong, strptr, ulong)

   FUNCTION
        Runs a command on your process/cli.  Seglist may be any language,
        including BCPL programs.  Stacksize is in bytes.  argptr is a null-
        terminated string, argsize is its length.  Returns the returncode the
        program exited with in d0. Returns -1 if the stack couldn't be
        allocated.

        NOTE: the argument string MUST be terminated with a newline to work
        properly with readargs() and other argument parsers.

        RunCommand also takes care of setting up the current input filehandle
        in such a way that readargs() can be used in the program, and restores
        the state of the buffering before returning.  It also sets the value
        returned by getargstr(), and restores it before returning.  note:
        the setting of the argument string in the filehandle was added in V37.

        It's usually appropriate to set the command name (via
        setprogramname()) before calling runcommand().  runcommand() sets
        the value returned by getargstr() while the command is running.

   INPUTS
        seglist   - Seglist of command to run.
        stacksize - Number of bytes to allocate for stack space
        argptr    - Pointer to argument command string.
        argsize   - Number of bytes in argument command.

   RESULT
        rc        - Return code from executed command. -1 indicates failure

   SEE ALSO
        createnewproc(), systemtaglist(), execute(), getargstr(),
        setprogramname(), readargs()