# `pipes` --- shell pipelines 介面

原始碼：Lib/pipes.py

Deprecated since version 3.11, will be removed in version 3.13: `pipes` 模組 (module) 即將被棄用（詳見 PEP 594）。請改用 `subprocess`。

The `pipes` module defines a class to abstract the concept of a pipeline --- a sequence of converters from one file to another.

Because the module uses /bin/sh command lines, a POSIX or compatible shell for `os.system()` and `os.popen()` is required.

Availability: Unix, not VxWorks.

The `pipes` module defines the following class:

class pipes.Template

  An abstraction of a pipeline.

範例：

    >>> import pipes
    >>> t = pipes.Template()
    >>> t.append('tr a-z A-Z', '--')
    >>> f = t.open('pipefile', 'w')
    >>> f.write('hello world')
    >>> f.close()
    >>> open('pipefile').read()
    'HELLO WORLD'

## Template Objects

Template objects following methods:

Template.reset()

  Restore a pipeline template to its initial state.

Template.clone()

  Return a new, equivalent, pipeline template.

Template.debug(flag)

  If 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 `set -x` command to be more verbose.

Template.append(cmd, kind)

  Append a new action at the end. The cmd variable must be a valid bourne shell command. The kind variable consists of two letters.

  The first letter can be either of `'-'` (which means the command reads its standard input), `'f'` (which means the commands reads a given file on the command line) or `'.'` (which means the commands reads no input, and hence must be first.)

  Similarly, the second letter can be either of `'-'` (which means the command writes to standard output), `'f'` (which means the command writes a file on the command line) or `'.'` (which means the command does not write anything, and hence must be last.)

Template.prepend(cmd, kind)

  Add a new action at the beginning. See `append()` for explanations of the arguments.

Template.open(file, mode)

  Return a file-like object, open to file, but read from or written to by the pipeline. Note that only one of `'r'`, `'w'` may be given.

Template.copy(infile, outfile)

  Copy infile to outfile through the pipe.