pipes — Interface to shell pipelines¶
Source code: Lib/pipes.py
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.
The pipes module defines the following class:
- 
class pipes.Template¶
- An abstraction of a pipeline. 
Example:
>>> 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 -xcommand 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. 
