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annotate Doc/lib/libselect.tex @ 8831:00a6bb65ff29 legacy-trunk

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Getting rid of this ancient stuff.
author Guido van Rossum <guido@python.org>
date Wed, 05 Aug 1998 21:10:09 +0000
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1 \section{Built-in Module \module{select}}
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2 \declaremodule{builtin}{select}
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3
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4 \modulesynopsis{Wait for I/O completion on multiple streams.}
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5
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6
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7 This module provides access to the function \cfunction{select()}
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8 available in most \UNIX{} versions. It defines the following:
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9
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10 \begin{excdesc}{error}
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11 The exception raised when an error occurs. The accompanying value is
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12 a pair containing the numeric error code from \cdata{errno} and the
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13 corresponding string, as would be printed by the \C{} function
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14 \cfunction{perror()}.
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15 \end{excdesc}
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16
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17 \begin{funcdesc}{select}{iwtd, owtd, ewtd\optional{, timeout}}
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18 This is a straightforward interface to the \UNIX{} \cfunction{select()}
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19 system call. The first three arguments are lists of `waitable
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20 objects': either integers representing \UNIX{} file descriptors or
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21 objects with a parameterless method named \method{fileno()} returning
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22 such an integer. The three lists of waitable objects are for input,
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23 output and `exceptional conditions', respectively. Empty lists are
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24 allowed. The optional \var{timeout} argument specifies a time-out as a
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25 floating point number in seconds. When the \var{timeout} argument
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26 is omitted the function blocks until at least one file descriptor is
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27 ready. A time-out value of zero specifies a poll and never blocks.
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28
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29 The return value is a triple of lists of objects that are ready:
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30 subsets of the first three arguments. When the time-out is reached
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31 without a file descriptor becoming ready, three empty lists are
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32 returned.
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33
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34 Amongst the acceptable object types in the lists are Python file
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35 objects (e.g. \code{sys.stdin}, or objects returned by
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36 \function{open()} or \function{os.popen()}), socket objects
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37 returned by \function{socket.socket()},%
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38 \withsubitem{(in module socket)}{\ttindex{socket()}}
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39 \withsubitem{(in module posix)}{\ttindex{popen()}}
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40 \withsubitem{(in module os)}{\ttindex{popen()}}
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41 and the module \module{stdwin}\refbimodindex{stdwin} which happens to
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42 define a function \function{fileno()}%
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43 \withsubitem{(in module stdwin)}{\ttindex{fileno()}}
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44 for just this purpose. You may
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45 also define a \dfn{wrapper} class yourself, as long as it has an
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46 appropriate \method{fileno()} method (that really returns a \UNIX{}
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47 file descriptor, not just a random integer).
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48 \end{funcdesc}