file_spec

    The full file specification of a new image to be activated in the
    child process.

 arg0, ...

    A sequence of pointers to null-terminated character strings.

    If the POSIX-1 format is used, at least one argument must be
    present and must point to a string that is the same as the new
    process filename (or its last component). (This pointer can also
    be the NULL pointer, but then execle would accomplish nothing.)
    The last pointer must be the NULL pointer. This is also the
    convention if the compatibility format is used.