Fred Drake | 4755e7d | 1999-06-21 18:25:49 +0000 | [diff] [blame] | 1 | \section{\module{pipes} --- |
| 2 | Interface to shell pipelines} |
| 3 | |
| 4 | \declaremodule{standard}{pipes} |
| 5 | \platform{Unix} |
Fred Drake | 57657bc | 2000-12-01 15:25:23 +0000 | [diff] [blame^] | 6 | \sectionauthor{Moshe Zadka}{moshez@zadka.site.co.il} |
Fred Drake | 4755e7d | 1999-06-21 18:25:49 +0000 | [diff] [blame] | 7 | \modulesynopsis{A Python interface to \UNIX{} shell pipelines.} |
| 8 | |
| 9 | |
| 10 | The \module{pipes} module defines a class to abstract the concept of |
| 11 | a \emph{pipeline} --- a sequence of convertors from one file to |
| 12 | another. |
| 13 | |
| 14 | Because the module uses \program{/bin/sh} command lines, a \POSIX{} or |
| 15 | compatible shell for \function{os.system()} and \function{os.popen()} |
| 16 | is required. |
| 17 | |
| 18 | The \module{pipes} module defines the following class: |
| 19 | |
| 20 | \begin{classdesc}{Template}{} |
| 21 | An abstraction of a pipeline. |
Fred Drake | d5d55ea | 1999-06-21 18:36:09 +0000 | [diff] [blame] | 22 | \end{classdesc} |
Fred Drake | 4755e7d | 1999-06-21 18:25:49 +0000 | [diff] [blame] | 23 | |
| 24 | Example: |
| 25 | |
| 26 | \begin{verbatim} |
| 27 | >>> import pipes |
| 28 | >>> t=pipes.Template() |
| 29 | >>> t.append('tr a-z A-Z', '--') |
| 30 | >>> f=t.open('/tmp/1', 'w') |
| 31 | >>> f.write('hello world') |
| 32 | >>> f.close() |
| 33 | >>> open('/tmp/1').read() |
| 34 | 'HELLO WORLD' |
| 35 | \end{verbatim} |
| 36 | |
| 37 | |
| 38 | \subsection{Template Objects \label{template-objects}} |
| 39 | |
| 40 | Template objects following methods: |
| 41 | |
| 42 | \begin{methoddesc}{reset}{} |
| 43 | Restore a pipeline template to its initial state. |
| 44 | \end{methoddesc} |
| 45 | |
| 46 | \begin{methoddesc}{clone}{} |
| 47 | Return a new, equivalent, pipeline template. |
| 48 | \end{methoddesc} |
| 49 | |
| 50 | \begin{methoddesc}{debug}{flag} |
| 51 | If \var{flag} is true, turn debugging on. Otherwise, turn debugging |
| 52 | off. When debugging is on, commands to be executed are printed, and |
| 53 | the shell is given \code{set -x} command to be more verbose. |
| 54 | \end{methoddesc} |
| 55 | |
| 56 | \begin{methoddesc}{append}{cmd, kind} |
| 57 | Append a new action at the end. The \var{cmd} variable must be a valid |
| 58 | bourne shell command. The \var{kind} variable consists of two letters. |
| 59 | |
| 60 | The first letter can be either of \code{'-'} (which means the command |
| 61 | reads its standard input), \code{'f'} (which means the commands reads |
| 62 | a given file on the command line) or \code{'.'} (which means the commands |
| 63 | reads no input, and hence must be first.) |
| 64 | |
Thomas Wouters | f831663 | 2000-07-16 19:01:10 +0000 | [diff] [blame] | 65 | Similarly, the second letter can be either of \code{'-'} (which means |
Fred Drake | 4755e7d | 1999-06-21 18:25:49 +0000 | [diff] [blame] | 66 | the command writes to standard output), \code{'f'} (which means the |
| 67 | command writes a file on the command line) or \code{'.'} (which means |
| 68 | the command does not write anything, and hence must be last.) |
| 69 | \end{methoddesc} |
| 70 | |
| 71 | \begin{methoddesc}{prepend}{cmd, kind} |
| 72 | Add a new action at the beginning. See \method{append()} for explanations |
| 73 | of the arguments. |
| 74 | \end{methoddesc} |
| 75 | |
| 76 | \begin{methoddesc}{open}{file, mode} |
| 77 | Return a file-like object, open to \var{file}, but read from or |
| 78 | written to by the pipeline. Note that only one of \code{'r'}, |
| 79 | \code{'w'} may be given. |
| 80 | \end{methoddesc} |
| 81 | |
| 82 | \begin{methoddesc}{copy}{infile, outfile} |
| 83 | Copy \var{infile} to \var{outfile} through the pipe. |
| 84 | \end{methoddesc} |