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| -rw-r--r-- | Doc/lib/libselect.tex | 28 |
1 files changed, 15 insertions, 13 deletions
diff --git a/Doc/lib/libselect.tex b/Doc/lib/libselect.tex index 44398aa..b79f5c2 100644 --- a/Doc/lib/libselect.tex +++ b/Doc/lib/libselect.tex @@ -33,14 +33,16 @@ polling objects. \begin{funcdesc}{select}{iwtd, owtd, ewtd\optional{, timeout}} This is a straightforward interface to the \UNIX{} \cfunction{select()} system call. The first three arguments are lists of `waitable -objects': either integers representing \UNIX{} file descriptors or +objects': either integers representing file descriptors or objects with a parameterless method named \method{fileno()} returning such an integer. The three lists of waitable objects are for input, output and `exceptional conditions', respectively. Empty lists are -allowed. The optional \var{timeout} argument specifies a time-out as a -floating point number in seconds. When the \var{timeout} argument -is omitted the function blocks until at least one file descriptor is -ready. A time-out value of zero specifies a poll and never blocks. +allowed, but acceptance of three empty lists is platform-dependent. +(It is known to work on \UNIX{} but not on Windows.) The optional +\var{timeout} argument specifies a time-out as a floating point number +in seconds. When the \var{timeout} argument is omitted the function +blocks until at least one file descriptor is ready. A time-out value +of zero specifies a poll and never blocks. The return value is a triple of lists of objects that are ready: subsets of the first three arguments. When the time-out is reached @@ -52,14 +54,14 @@ objects (e.g. \code{sys.stdin}, or objects returned by \function{open()} or \function{os.popen()}), socket objects returned by \function{socket.socket()},% \withsubitem{(in module socket)}{\ttindex{socket()}} -\withsubitem{(in module os)}{\ttindex{popen()}} -and the module \module{stdwin}\refbimodindex{stdwin} which happens to -define a function -\function{fileno()}\withsubitem{(in module stdwin)}{\ttindex{fileno()}} -for just this purpose. You may -also define a \dfn{wrapper} class yourself, as long as it has an -appropriate \method{fileno()} method (that really returns a \UNIX{} -file descriptor, not just a random integer). +\withsubitem{(in module os)}{\ttindex{popen()}}. +You may also define a \dfn{wrapper} class yourself, as long as it has +an appropriate \method{fileno()} method (that really returns a file +descriptor, not just a random integer). +\strong{Note:}\index{WinSock} File objects on Windows are not +acceptable, but sockets are. On Windows, the underlying +\cfunction{select()} function is provided by the WinSock library, and +does not handle file desciptors that don't originate from WinSock. \end{funcdesc} \subsection{Polling Objects |