mirror of https://github.com/apache/cloudstack.git
Fancy line editor for Ian
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Leo Simons
wilderrodrigues
parent
3ab83fdba7
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6244265de0
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#!/usr/bin/python
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# Licensed to the Apache Software Foundation (ASF) under one
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# or more contributor license agreements. See the NOTICE file
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# distributed with this work for additional information
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# regarding copyright ownership. The ASF licenses this file
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# to you under the Apache License, Version 2.0 (the
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# "License"); you may not use this file except in compliance
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# with the License. You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing,
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# software distributed under the License is distributed on an
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# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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# KIND, either express or implied. See the License for the
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# specific language governing permissions and limitations
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# under the License.
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import logging
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import re
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import shutil
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import os
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class LineEdit(object):
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"""Helper for LineEditingFile that keeps track of one edit."""
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def __init__(self, search, sub, *sub_args, **kwargs):
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if len(sub_args) > 0:
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sub = sub % sub_args
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flags = kwargs.get('flags', 0)
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self.pattern = re.compile(search, flags=flags)
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self.sub = sub
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self.count = kwargs.get('count', 0) # max subs to make
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self.subs = 0 # subs made so far
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class LineEditingFile(object):
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"""
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Atomic, conservative, by-line editing of configuration files.
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Will not touch the file if there are no changes to do.
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Reasonably efficient for large files, though files with a long time
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before their first match will use memory.
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Given a vhosts file such as:
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>>> with open('doctest-vhosts.conf', 'w') as f:
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... f.write('''
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... Listen foo:80
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... <VirtualHost foo:80>
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... DocRoot /var/www
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... </VirtualHost>
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...
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... Listen other:80
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... <VirtualHost other:80>
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... DocRoot /var/www
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... </VirtualHost>
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... ''')
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...
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To replace the hostname for the first virtualhost entry:
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>>> new_hostname = 'fooooo'
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>>> with LineEditingFile('doctest-vhosts.conf') as f:
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... f.replace(r'<VirtualHost .*?:80>', '<VirtualHost %s:80>', new_hostname, count=1, flags=re.I)
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... f.replace(r'Listen .*?:80', 'Listen %s:80', new_hostname, count=1, flags=re.I)
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...
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Be careful with the matches!
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A second invocation of the same rule will edit the second vhost:
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>>> new_hostname = 'fooooo'
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>>> with LineEditingFile('doctest-vhosts.conf') as f:
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... f.replace(r'<VirtualHost .*?:80>', '<VirtualHost %s:80>', new_hostname, count=1, flags=re.I)
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...
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To move all hosts from port 80 to port 8080:
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>>> with LineEditingFile('doctest-vhosts.conf') as f:
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... f.replace(r'<VirtualHost (.*?):80>', '<VirtualHost \\\\1:8080>', flags=re.I)
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... f.replace(r'Listen (.*?):80', 'Listen \\\\1:80', flags=re.I)
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...
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(please note in this example there's a double escape of the backreference
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\\\\1, to make the example work with doctest)
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Since this example already matched all files, a second invocation does nothing:
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>>> with LineEditingFile('doctest-vhosts.conf') as f:
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... f.replace(r'<VirtualHost (.*?):80>', '<VirtualHost \\\\1:8080>', flags=re.I)
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...
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It's also acceptable to not make any edits at all:
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>>> with LineEditingFile('doctest-vhosts.conf') as f:
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... pass
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...
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You don't _have_ to use a with statement:
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>>> f = LineEditingFile('doctest-vhosts.conf')
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>>> f.replace(r'DocRoot /var/www', 'DocRoot /var/www/html', flags=re.I)
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>>> changes = f.commit()
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>>> print changes
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2
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>>>
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Cleanup of the example vhosts.conf:
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>>> # noinspection PyBroadException
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>>> try:
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... os.unlink('doctest-vhosts.conf')
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... os.unlink('doctest-vhosts.conf.bak')
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... os.unlink('doctest-vhosts.conf.new')
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... except:
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... pass
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...
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"""
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def __init__(self, filename):
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self.filename = filename
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self.changed = False
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self.edits = []
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def __enter__(self):
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return self
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def replace(self, search, sub, *sub_args, **kwargs):
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edit = LineEdit(search, sub, *sub_args, **kwargs)
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self.edits.append(edit)
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# noinspection PyUnusedLocal
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def __exit__(self, exc, value, traceback):
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if exc is not None:
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return False # return false results in re-raise
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self.commit()
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def commit(self):
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changes = 0
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changed_file = None
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changed_filename = self.filename + '.new'
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try:
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lines = []
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backup_filename = self.filename + '.bak'
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# noinspection PyUnusedLocal
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stat = None
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with open(self.filename, 'r') as orig:
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stat = os.fstat(orig.fileno())
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for line in orig:
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changed_line = line
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for edit in self.edits:
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remaining_count = 0
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if edit.count != 0:
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remaining_count = edit.count - edit.subs
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if remaining_count < 0:
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raise Exception("Made too many edits")
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elif remaining_count == 0:
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continue
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changed_line, subs = edit.pattern.subn(
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edit.sub, line, remaining_count)
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if changed_line != line:
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if changed_file is None:
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logging.debug("Editing file %s" % self.filename)
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logging.debug(" - %s" % line[:-1])
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logging.debug(" + %s" % changed_line[:-1])
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changes += subs
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edit.subs += subs
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if changes == 0: # buffer until we find a change
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lines.append(changed_line)
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elif changed_file is None: # found first change, flush buffer
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changed_file = open(changed_filename, 'w')
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if hasattr(os, 'fchmod'):
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os.fchmod(changed_file.fileno(), # can cause OSError which aborts
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stat.st_mode)
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if hasattr(os, 'fchown'):
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os.fchown(changed_file.fileno(), # can cause OSError which aborts
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stat.st_uid, stat.st_gid)
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changed_file.writelines(lines)
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changed_file.write(changed_line)
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del lines # reclaim buffer memory
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else: # already flushed, just write
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changed_file.write(changed_line)
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if changes == 0:
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logging.info("No edits need for file %s" %
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self.filename)
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else:
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changed_file.close()
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changed_file = None
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if os.path.exists(backup_filename): # back up the original
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os.unlink(backup_filename)
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shutil.copy(self.filename, backup_filename)
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os.rename(changed_filename, self.filename) # the swap
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logging.info("Edited file %s (%d changes)" %
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(self.filename, changes))
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finally:
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if changed_file is not None: # failed, clean up
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changed_file.close()
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os.unlink(changed_filename)
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return changes
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if __name__ == "__main__":
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logging.basicConfig(level=logging.DEBUG)
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import doctest
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doctest.testmod()
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