pipes — Interface to shell pipelines
Platforms: Unix
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('/tmp/1', 'w')
>>> f.write('hello world')
>>> f.close()
>>> open('/tmp/1').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.