\section{\module{pipes} ---         Interface to shell pipelines} \declaremodule{standard}{pipes}  \platform{Unix}\sectionauthor{Moshe Zadka}{moshez@zadka.site.co.il}\modulesynopsis{A Python interface to \UNIX\ shell pipelines.}  The \module{pipes} module defines a class to abstract the concept ofa \emph{pipeline} --- a sequence of converters from one file to another. Because the module uses \program{/bin/sh} command lines, a \POSIX{} orcompatible shell for \function{os.system()} and \function{os.popen()}is required. The \module{pipes} module defines the following class: \begin{classdesc}{Template}{}An abstraction of a pipeline.\end{classdesc} Example: \begin{verbatim}>>> import pipes>>> t=pipes.Template()>>> t.append('tr a-z A-Z', '--')>>> f=t.open('/tmp/1', 'w')>>> f.write('hello world')>>> f.close()>>> open('/tmp/1').read()'HELLO WORLD'\end{verbatim}  \subsection{Template Objects \label{template-objects}} Template objects following methods: \begin{methoddesc}{reset}{}Restore a pipeline template to its initial state.\end{methoddesc} \begin{methoddesc}{clone}{}Return a new, equivalent, pipeline template.\end{methoddesc} \begin{methoddesc}{debug}{flag}If \var{flag} is true, turn debugging on. Otherwise, turn debuggingoff. When debugging is on, commands to be executed are printed, andthe shell is given \code{set -x} command to be more verbose.\end{methoddesc} \begin{methoddesc}{append}{cmd, kind}Append a new action at the end. The \var{cmd} variable must be a validbourne shell command. The \var{kind} variable consists of two letters. The first letter can be either of \code{'-'} (which means the commandreads its standard input), \code{'f'} (which means the commands readsa given file on the command line) or \code{'.'} (which means the commandsreads no input, and hence must be first.) Similarly, the second letter can be either of \code{'-'} (which means the command writes to standard output), \code{'f'} (which means the command writes a file on the command line) or \code{'.'} (which meansthe command does not write anything, and hence must be last.)\end{methoddesc} \begin{methoddesc}{prepend}{cmd, kind}Add a new action at the beginning. See \method{append()} for explanationsof the arguments.\end{methoddesc} \begin{methoddesc}{open}{file, mode}Return a file-like object, open to \var{file}, but read from orwritten to by the pipeline.  Note that only one of \code{'r'},\code{'w'} may be given.\end{methoddesc} \begin{methoddesc}{copy}{infile, outfile}Copy \var{infile} to \var{outfile} through the pipe.\end{methoddesc}