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import os
def sort_file(filename, mapping):
"""
Sorts a passwd or group file based on the numeric ID in the third column.
If a mapping is given, the name from the first column is mapped via that
dictionary instead (necessary for /etc/shadow and /etc/gshadow). If not,
a new mapping is created on the fly and returned.
"""
new_mapping = {}
with open(filename, 'rb+') as f:
lines = f.readlines()
# No explicit error checking for the sake of simplicity. /etc
# files are assumed to be well-formed, causing exceptions if
# not.
for line in lines:
entries = line.split(b':')
name = entries[0]
if mapping is None:
id = int(entries[2])
else:
id = mapping[name]
new_mapping[name] = id
# Sort by numeric id first, with entire line as secondary key
# (just in case that there is more than one entry for the same id).
lines.sort(key=lambda line: (new_mapping[line.split(b':')[0]], line))
# We overwrite the entire file, i.e. no truncate() necessary.
f.seek(0)
f.write(b''.join(lines))
return new_mapping
def sort_passwd(sysconfdir):
"""
Sorts passwd and group files in a rootfs /etc directory by ID.
"""
for suffix in '', '-':
for main, shadow in (('passwd', 'shadow'),
('group', 'gshadow')):
filename = os.path.join(sysconfdir, main + suffix)
if os.path.exists(filename):
mapping = sort_file(filename, None)
filename = os.path.join(sysconfdir, shadow + suffix)
if os.path.exists(filename):
sort_file(filename, mapping)
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