| \section{\module{pipes} --- |
| Interface to shell pipelines} |
| |
| \declaremodule{standard}{pipes} |
| \platform{Unix} |
| \sectionauthor{Moshe Zadka}{mzadka@geocities.com} |
| \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 convertors 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{funcdesc} |
| |
| 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.) |
| |
| Similarily, 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} |