1 :mod:`pipes` --- Interface to shell pipelines 2 ============================================= 3 4 .. module:: pipes 5 :platform: Unix 6 :synopsis: A Python interface to Unix shell pipelines. 7 8 .. sectionauthor:: Moshe Zadka <moshez (a] zadka.site.co.il> 9 10 **Source code:** :source:`Lib/pipes.py` 11 12 -------------- 13 14 The :mod:`pipes` module defines a class to abstract the concept of a *pipeline* 15 --- a sequence of converters from one file to another. 16 17 Because the module uses :program:`/bin/sh` command lines, a POSIX or compatible 18 shell for :func:`os.system` and :func:`os.popen` is required. 19 20 The :mod:`pipes` module defines the following class: 21 22 23 .. class:: Template() 24 25 An abstraction of a pipeline. 26 27 Example:: 28 29 >>> import pipes 30 >>> t = pipes.Template() 31 >>> t.append('tr a-z A-Z', '--') 32 >>> f = t.open('pipefile', 'w') 33 >>> f.write('hello world') 34 >>> f.close() 35 >>> open('pipefile').read() 36 'HELLO WORLD' 37 38 39 .. _template-objects: 40 41 Template Objects 42 ---------------- 43 44 Template objects following methods: 45 46 47 .. method:: Template.reset() 48 49 Restore a pipeline template to its initial state. 50 51 52 .. method:: Template.clone() 53 54 Return a new, equivalent, pipeline template. 55 56 57 .. method:: Template.debug(flag) 58 59 If *flag* is true, turn debugging on. Otherwise, turn debugging off. When 60 debugging is on, commands to be executed are printed, and the shell is given 61 ``set -x`` command to be more verbose. 62 63 64 .. method:: Template.append(cmd, kind) 65 66 Append a new action at the end. The *cmd* variable must be a valid bourne shell 67 command. The *kind* variable consists of two letters. 68 69 The first letter can be either of ``'-'`` (which means the command reads its 70 standard input), ``'f'`` (which means the commands reads a given file on the 71 command line) or ``'.'`` (which means the commands reads no input, and hence 72 must be first.) 73 74 Similarly, the second letter can be either of ``'-'`` (which means the command 75 writes to standard output), ``'f'`` (which means the command writes a file on 76 the command line) or ``'.'`` (which means the command does not write anything, 77 and hence must be last.) 78 79 80 .. method:: Template.prepend(cmd, kind) 81 82 Add a new action at the beginning. See :meth:`append` for explanations of the 83 arguments. 84 85 86 .. method:: Template.open(file, mode) 87 88 Return a file-like object, open to *file*, but read from or written to by the 89 pipeline. Note that only one of ``'r'``, ``'w'`` may be given. 90 91 92 .. method:: Template.copy(infile, outfile) 93 94 Copy *infile* to *outfile* through the pipe. 95 96
