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85 lines
3 KiB
TeX
85 lines
3 KiB
TeX
% Module and documentation by Eric S. Raymond, 21 Dec 1998
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\section{\module{shlex} ---
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Simple lexical analysis.}
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\declaremodule{standard}{shlex}
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\modulesynopsis{Simple lexical analysis for \UNIX{} shell-like languages.}
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\moduleauthor{Eric S. Raymond}{esr@snark.thyrsus.com}
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\sectionauthor{Eric S. Raymond}{esr@snark.thyrsus.com}
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\versionadded{1.5.2}
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The \class{shlex} class makes it easy to write lexical analyzers for
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simple syntaxes resembling that of the \UNIX{} shell. This will often
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be useful for writing minilanguages, e.g.\ in run control files for
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Python applications.
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\begin{classdesc}{shlex}{\optional{stream}}
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A \class{shlex} instance or subclass instance is a lexical analyzer
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object. The initialization argument, if present, specifies where to
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read characters from. It must be a file- or stream-like object with
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\method{read()} and \method{readline()} methods. If no argument is given,
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input will be taken from \code{sys.stdin}.
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\end{classdesc}
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\subsection{shlex Objects \label{shlex-objects}}
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A \class{shlex} instance has the following methods:
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\begin{methoddesc}{get_token}{}
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Return a token. If tokens have been stacked using
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\method{push_token()}, pop a token off the stack. Otherwise, read one
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from the input stream. If reading encounters an immediate
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end-of-file, an empty string is returned.
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\end{methoddesc}
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\begin{methoddesc}{push_token}{str}
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Push the argument onto the token stack.
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\end{methoddesc}
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Instances of \class{shlex} subclasses have some public instance
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variables which either control lexical analysis or can be used
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for debugging:
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\begin{memberdesc}{commenters}
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The string of characters that are recognized as comment beginners.
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All characters from the comment beginner to end of line are ignored.
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Includes just \character{\#} by default.
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\end{memberdesc}
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\begin{memberdesc}{wordchars}
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The string of characters that will accumulate into multi-character
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tokens. By default, includes all \ASCII{} alphanumerics and
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underscore.
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\end{memberdesc}
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\begin{memberdesc}{whitespace}
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Characters that will be considered whitespace and skipped. Whitespace
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bounds tokens. By default, includes space, tab, linefeed and
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carriage-return.
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\end{memberdesc}
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\begin{memberdesc}{quotes}
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Characters that will be considered string quotes. The token
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accumulates until the same quote is encountered again (thus, different
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quote types protect each other as in the shall.) By default, includes
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\ASCII{} single and double quotes.
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\end{memberdesc}
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Note that any character not declared to be a word character,
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whitespace, or a quote will be returned as a single-character token.
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Quote and comment characters are not recognized within words. Thus,
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the bare words \samp{ain't} and \samp{ain\#t} would be returned as single
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tokens by the default parser.
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\begin{memberdesc}{lineno}
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Source line number (count of newlines seen so far plus one).
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\end{memberdesc}
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\begin{memberdesc}{token}
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The token buffer. It may be useful to examine this when catching
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exceptions.
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\end{memberdesc}
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