A ``None`` value indicates that the process has not terminated yet.
- A negative value ``-N`` indicates that the child was terminated
- by signal ``N`` (POSIX only).
+ For processes created with :func:`~asyncio.create_subprocess_exec`, a negative
+ value ``-N`` indicates that the child was terminated by signal ``N``
+ (POSIX only).
+
+ For processes created with :func:`~asyncio.create_subprocess_shell`, the
+ return code reflects the exit status of the shell itself (e.g. ``/bin/sh``),
+ which may map signals to codes such as ``128+N``. See the
+ documentation of the shell (for example, the Bash manual's Exit Status)
+ for details.
+
.. _asyncio-subprocess-threads:
A negative value ``-N`` indicates that the child was terminated by signal
``N`` (POSIX only).
+ When ``shell=True``, the return code reflects the exit status of the shell
+ itself (e.g. ``/bin/sh``), which may map signals to codes such as
+ ``128+N``. See the documentation of the shell (for example, the Bash
+ manual's Exit Status) for details.
+
Windows Popen Helpers
---------------------