44 lines
2.0 KiB
TeX
44 lines
2.0 KiB
TeX
\section{Built-in Module \sectcode{select}}
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\label{module-select}
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\bimodindex{select}
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This module provides access to the function \code{select} available in
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most \UNIX{} versions. It defines the following:
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\setindexsubitem{(in module select)}
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\begin{excdesc}{error}
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The exception raised when an error occurs. The accompanying value is
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a pair containing the numeric error code from \code{errno} and the
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corresponding string, as would be printed by the C function
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\code{perror()}.
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\end{excdesc}
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\begin{funcdesc}{select}{iwtd\, owtd\, ewtd\optional{\, timeout}}
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This is a straightforward interface to the \UNIX{} \code{select()}
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system call. The first three arguments are lists of `waitable
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objects': either integers representing \UNIX{} file descriptors or
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objects with a parameterless method named \code{fileno()} returning
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such an integer. The three lists of waitable objects are for input,
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output and `exceptional conditions', respectively. Empty lists are
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allowed. The optional \var{timeout} argument specifies a time-out as a
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floating point number in seconds. When the \var{timeout} argument
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is omitted the function blocks until at least one file descriptor is
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ready. A time-out value of zero specifies a poll and never blocks.
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The return value is a triple of lists of objects that are ready:
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subsets of the first three arguments. When the time-out is reached
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without a file descriptor becoming ready, three empty lists are
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returned.
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Amongst the acceptable object types in the lists are Python file
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objects (e.g. \code{sys.stdin}, or objects returned by \code{open()}
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or \code{posix.popen()}), socket objects returned by
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\code{socket.socket()}, and the module \code{stdwin} which happens to
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define a function \code{fileno()} for just this purpose. You may
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also define a \dfn{wrapper} class yourself, as long as it has an
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appropriate \code{fileno()} method (that really returns a \UNIX{} file
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descriptor, not just a random integer).
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\end{funcdesc}
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\ttindex{socket}
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\ttindex{stdwin}
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