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: / snap / core22 / 1981 / usr / share / subiquity / subiquitycore /
Filename : file_util.py
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# Copyright 2018-2022 Canonical, Ltd.
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, version 3.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

import contextlib
import datetime
import grp
import os
import tempfile

import yaml

_DEF_PERMS = 0o640
_DEF_GROUP = 'adm'


@contextlib.contextmanager
def open_perms(filename, *, cmode=None):
    if cmode is None:
        cmode = _DEF_PERMS

    tf = None
    try:
        dirname = os.path.dirname(filename)
        os.makedirs(dirname, exist_ok=True)
        tf = tempfile.NamedTemporaryFile(dir=dirname, delete=False, mode='w')
        yield tf
        tf.close()
        os.chmod(tf.name, cmode)
        if os.getuid() == 0:
            os.chown(tf.name, -1, grp.getgrnam(_DEF_GROUP).gr_gid)
        os.rename(tf.name, filename)
    except OSError as e:
        if tf is not None:
            os.unlink(tf.name)
        raise e


def write_file(filename, content, **kwargs):
    with open_perms(filename, **kwargs) as tf:
        tf.write(content)


def generate_config_yaml(filename, content, **kwargs):
    with open_perms(filename, **kwargs) as tf:
        now = datetime.datetime.utcnow()
        tf.write(f'# Autogenerated by Subiquity: {now} UTC\n')
        tf.write(yaml.dump(content))