free_beer.py

#!/usr/bin/python3

import sh
import re

HUMANS = ['jkane', 'djames', 'mkirk']


def clean_passwd(h, humans):
    clean = []
    for row in h:
        user = row.split(':')
        if user[0] not in humans:
            clean.append(row.strip())
        else:
            print('Removing %r' % user[0])

    return "\n".join(clean) + "\n"

def clean_group(h, humans):
    clean = []
    for row in h:
        group = row.split(':')
        users = group[-1].split(',')

        new_users = []
        for user in users:
            user = user.strip()
            if user not in humans:
                new_users.append(user)
            else:
                print('Removing %r from group %r' % (user, group[0]))

        group[-1] = ",".join(new_users)
        if group[0] not in humans:
            clean.append(':'.join(group))
        else:
            print('Removing group %r' % group[0])


    return "\n".join(clean) + "\n"

def clean_shadow(h, humans):
    """format of /etc/shadow is close-enough to password for our purposes"""
    return clean_passwd(h, humans)


for human in HUMANS:
    try:
        uid, gid, groups = sh.id(human).split()
    except sh.ErrorReturnCode_1:
        print('Human %r not found.' % human)
        continue

    old_uid = int(re.search("uid=(\d*)\(.*", uid).group(1))
    old_gid = int(re.search("gid=(\d*)\(.*", gid).group(1))

    print("Human %r was uid %r / gid %r" % (human, old_uid, old_gid))

    with open('/etc/passwd', 'r') as h:
        clean = clean_passwd(h, [human])
    with open('/etc/passwd', 'w') as h:
        h.write(clean)

    with open('/etc/group', 'r') as h:
        clean = clean_group(h, [human])
    with open('/etc/group', 'w') as h:
        h.write(clean)

    with open('/etc/shadow', 'r') as h:
        clean = clean_shadow(h, [human])
    with open('/etc/shadow', 'w') as h:
        h.write(clean)  

    try:
        uid, gid, groups = sh.id(human).split()
    except sh.ErrorReturnCode_1:
        print('Human %r not found.' % human)
        continue

    new_uid = int(re.search("uid=(\d*)\(.*", uid).group(1))
    new_gid = int(re.search("gid=(\d*)\(.*", gid).group(1))

    print("Human %r is now uid %r / gid %r" % (human, new_uid, new_gid))

    if new_uid != old_uid:
        # change every file owned by old_uid to be owned by this human
        sh.find("/", "-uid", old_uid, "-exec", "chown", human, "{}", "+")

    if new_gid != old_gid:
        # change every file owned by old_gid to be owned by the new group
        # the -h is to avoid reaching through symlinks and instead change the sym itself
        sh.find("/", "-gid", old_gid, "-exec", "chgrp", "-h", new_gid, "{}", "+")