+# replace a target file with a new contents - checks for changes
+# can handle chmod if requested
+# can also remove resulting file if contents are void, if requested
+# performs atomically:
+# writes in a tmp file, which is then renamed (from sliverauth originally)
+# returns True if a change occurred, or the file is deleted
+def replace_file_with_string (target, new_contents, chmod=None, remove_if_empty=False):
+ try:
+ current=file(target).read()
+ except:
+ current=""
+ if current==new_contents:
+ # if turns out to be an empty string, and remove_if_empty is set,
+ # then make sure to trash the file if it exists
+ if remove_if_empty and not new_contents and os.path.isfile(target):
+ logger.verbose("tools.replace_file_with_string: removing file %s"%target)
+ try: os.unlink(target)
+ finally: return True
+ return False
+ # overwrite target file: create a temp in the same directory
+ path=os.path.dirname(target) or '.'
+ fd, name = tempfile.mkstemp('','repl',path)
+ os.write(fd,new_contents)
+ os.close(fd)
+ if os.path.exists(target):
+ os.unlink(target)
+ os.rename(name,target)
+ if chmod: os.chmod(target,chmod)
+ return True
+
+# utilities functions to get (cached) information from the node
+
+# get node_id from /etc/planetlab/node_id and cache it
+_node_id=None
+def node_id():
+ global _node_id
+ if _node_id is None:
+ try:
+ _node_id=int(file("/etc/planetlab/node_id").read())
+ except:
+ _node_id=""
+ return _node_id
+
+# get slicefamily from /etc/planetlab/slicefamily and cache it
+# http://svn.planet-lab.org/wiki/SliceFamily
+_slicefamily=None
+def slicefamily():
+ global _slicefamily
+ if _slicefamily is None:
+ try:
+ _slicefamily=file("/etc/planetlab/slicefamily").read().strip()
+ except:
+ _slicefamily=""
+ return _slicefamily
+
+_root_context_arch=None
+def root_context_arch():
+ global _root_context_arch
+ if not _root_context_arch:
+ _root_context_arch=commands.getoutput("uname -i")
+ return _root_context_arch
+