Viewing file:  atomic_helper.py (1.33 KB) -rw-r--r--
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# This file is part of cloud-init. See LICENSE file for license information.
import json
import logging
import os
import stat
import tempfile
_DEF_PERMS = 0o644
LOG = logging.getLogger(__name__)
def write_file(filename, content, mode=_DEF_PERMS,
omode="wb", preserve_mode=False):
# open filename in mode 'omode', write content, set permissions to 'mode'
if preserve_mode:
try:
file_stat = os.stat(filename)
mode = stat.S_IMODE(file_stat.st_mode)
except OSError:
pass
tf = None
try:
tf = tempfile.NamedTemporaryFile(dir=os.path.dirname(filename),
delete=False, mode=omode)
LOG.debug(
"Atomically writing to file %s (via temporary file %s) - %s: [%o]"
" %d bytes/chars",
filename, tf.name, omode, mode, len(content))
tf.write(content)
tf.close()
os.chmod(tf.name, mode)
os.rename(tf.name, filename)
except Exception as e:
if tf is not None:
os.unlink(tf.name)
raise e
def write_json(filename, data, mode=_DEF_PERMS):
# dump json representation of data to file filename.
return write_file(
filename, json.dumps(data, indent=1, sort_keys=True) + "\n",
omode="w", mode=mode)
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