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Diffstat (limited to 'Doc/library/signal.rst')
| -rw-r--r-- | Doc/library/signal.rst | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/Doc/library/signal.rst b/Doc/library/signal.rst index 473eda2807..68a5d2c014 100644 --- a/Doc/library/signal.rst +++ b/Doc/library/signal.rst @@ -262,13 +262,17 @@ The :mod:`signal` module defines the following functions: .. function:: set_wakeup_fd(fd) - Set the wakeup fd to *fd*. When a signal is received, a ``'\0'`` byte is - written to the fd. This can be used by a library to wakeup a poll or select - call, allowing the signal to be fully processed. + Set the wakeup file descriptor to *fd*. When a signal is received, the + signal number is written as a single byte into the fd. This can be used by + a library to wakeup a poll or select call, allowing the signal to be fully + processed. The old wakeup fd is returned. *fd* must be non-blocking. It is up to the library to remove any bytes before calling poll or select again. + Use for example ``struct.unpack('%uB' % len(data), data)`` to decode the + signal numbers list. + When threads are enabled, this function can only be called from the main thread; attempting to call it from other threads will cause a :exc:`ValueError` exception to be raised. |