ref: 34f5a8333090c5090e1d0b6ddbaf900d64340eea
dir: /sys/src/cmd/python/Doc/lib/libpipes.tex/
\section{\module{pipes} --- Interface to shell pipelines} \declaremodule{standard}{pipes} \platform{Unix} \sectionauthor{Moshe Zadka}{[email protected]} \modulesynopsis{A Python interface to \UNIX\ shell pipelines.} The \module{pipes} module defines a class to abstract the concept of a \emph{pipeline} --- a sequence of converters from one file to another. Because the module uses \program{/bin/sh} command lines, a \POSIX{} or compatible 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 debugging off. When debugging is on, commands to be executed are printed, and the 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 valid bourne shell command. The \var{kind} variable consists of two letters. The first letter can be either of \code{'-'} (which means the command reads its standard input), \code{'f'} (which means the commands reads a given file on the command line) or \code{'.'} (which means the commands reads 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 means the 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 explanations of the arguments. \end{methoddesc} \begin{methoddesc}{open}{file, mode} Return a file-like object, open to \var{file}, but read from or written 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}