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hosts.py
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hosts.py
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import re, os
class Hosts(dict):
# do not expect update, items, keys, and values to work correctly
# on this weird dikshunnary
address=re.compile('(\d{1,3}\.){3}\d{1,3}')
def __init__(self, defaults=None, **kwargs):
self.dustbin = []
if type(defaults)==str:
self.filename=defaults
self.read(defaults)
elif hasattr(defaults,'__setitem__'):
if hasattr(defaults, 'dustbin'):
self.dustbin = defaults.dustbin
for a,h in defaults.items():
h=h.split()
self[a]=h.pop(0)
for i in h: self.append(a,i)
if kwargs:
for a,h in kwargs.items():
h=h.split()
self[a]=h.pop(0)
for i in h: self.append(a,i)
# update and items should be overidden
# Shortcut to the dict set and del methods (Hosts do no override get)
def dset(self,item, value): dict.__setitem__(self, item, value)
def ddel(self,item): dict.__delitem__(self, item)
def __setitem__(self, item, value):
if self.address.match(item) and not self.address.match(value):
a, h = item, value
elif self.address.match(value) and not self.address.match(item):
a, h = value, item
else:
raise Exception,"Error item '%s' or value '%s' must be an address " % (item,value)
# The address argument already exists
if a in self:
# Suppress every old hostname entries poing to a
for i in self[a].split(): self.ddel( i)
self.dset( a, h)
self.dset( h, a)
# The hostname argument already exists ( the address
# argument is unkown)
elif h in self:
olda = self[h]
h = self[olda]
# Creating the new address entry
self.dset(a, h)
# updating the entries pointing to the old address
for i in h.split(): self.dset(i,a)
# Suppress the old address entries poing to a
self.ddel( olda)
# The relation address -- hostname is new
else:
self.dset(a, h)
self.dset(h, a)
for i in a,h:
if i in self.dustbin: self.dustbin.remove(i)
def __delitem__(self,item):
if self.address.match(item):
a, h = item, self[item]
else:
a, h = self[item], self[self[item]]
for i in h.split() + [a]: self.ddel(i)
for i in a,h: self.dustbin.append(i)
def __repr__(self):
lines=[ "%s%s%s" % (a, "\t"*self.align(a), self[a]) for a in self.addresses() ]
if lines:
return "\n".join(lines)+'\n'
else: return ''
def align(self,a):
return ((23-len(a))/8+1)
def addresses(self):
a = [ a for a in self if self.address.match(a) ]
if '127.0.0.1' in sorted(a) :
a.remove('127.0.0.1')
a.insert(0, '127.0.0.1')
return a
def reprline(self,item):
if self.address.match(item):
a, h = item, self[item]
else:
a, h = self[item], self[self[item]]
return "%s%s%s" % (a, "\t"*((23-len(item))/8+1), h)
def append(self,item,value):
if self.address.match(item):
a, h = item, value
elif self.address.match(value):
a, h = value, item
else:
a, h = self[item], value
if self[a].find(h)!=-1: return
self.dset(a, "%s %s" % (self[a], h ))
self.dset(h, a)
def read(self,filenames):
"""Read and parse a filename or a list of filenames.
Files that cannot be opened are silently ignored; this is
designed so that you can specify a list of potential
configuration file locations (e.g. current directory, user's
home directory, systemwide directory), and all existing
configuration files in the list will be read. A single
filename may also be given.
Return list of successfully read files.
"""
if isinstance(filenames, basestring):
filenames = [filenames]
read_ok = []
for filename in filenames:
try:
fp = open(filename)
except IOError:
continue
self._read(fp)
fp.close()
read_ok.append(filename)
return read_ok
line=re.compile(
'''(^
(?P<address> (\d{1,3}\.){3}\d{1,3})
(?P<sep> \s+)
(?P<hostnames> (((?!\s+(\#|;)).)|\S)*)
)''', re.VERBOSE)
def _read(self, fp):
'''The file parameter can be a filename or a file
descriptor. The file should conform to the common hosts format'''
for l in fp:
m = self.line.match( l )
if not m: continue
a, h = m.group('address', 'hostnames')
if a:
h=h.split()
self[a]=h.pop(0)
for i in h: self.append(a,i)
def write(self, filename=None, order=None):
filename = filename or self.filename
# if we can write in an open file then we can write on stdout TODO...
# Because we pop the written lines, we need to pop on a _copy_
# Self must be filtered out from hostnames keys so that multi
# hostnames are properly handled.
c=Hosts( dict([ i for i in self.items() if self.address.match( i[0] ) ]) )
f=file(filename+'~','w')
if os.path.isfile(filename):
for l in file(filename):
m = c.line.match( l )
if not m:
f.write(l)
continue
a, h = m.group('address', 'hostnames')
if a:
# pops an address or hostname for the confile
# which is configured and which is not set for suppresion
i=[ i for i in h.split()+ [a] if i in c ]
if i:
i=i.pop()
if i not in c.dustbin:
f.write( self.line.sub( self.reprline(i), l ))
else : pass
del c[i]
else: f.write(l)
else: f.write(l)
f.write(repr(c))
f.close()
os.rename(filename+'~',filename)
if __name__=='__main__':
# une nouvelle relation
# un hostname qui change de nom
# un fqdn qui change d'addresse
# une suppression de relation
# le setitem ecrase les hostnames existant si l'adresse
# existe. Si le hostname existe et l'adresse est neuve:
# les hostnames sont balayes
# Ordering ...
print Hosts.line.match('1.0.0.1 localhost # very').groups()[0]
print Hosts.line.sub('127.0.0.1\t\tlocalhost','1.0.0.1 localhost # very')
h=Hosts()
h['mc']='10.0.0.1'
h['mc02']='10.0.0.2'
h.append('10.0.0.1','localhost')
print h.addresses()
print "2 lines, localhost is aliased\n", h
h['localhost'] = '10.0.0.3'
print "2 lines, localhost's addr is changed\n", h
h['10.0.0.3'] ='toto'
print "2 lines, localhost renamed toto\n", h
del h['toto']
del h['10.0.0.2']
print "2 lines deleted, nothin' left\n", h