虽然Python解释器可移植，并且许多标准库模块支持多个平台，但是有一些模块可以访问特定于平台的功能。本节中描述的模块仅在基于Unix的系统（如Linux，macOS，FreeBSD和OpenBSD）上提供访问功能。
pwd — Unix Password Database
目的：从Unix密码数据库中读取用户数据。
pwd模块可用于从Unix密码数据库（通常是/etc/passwd）读取用户信息。
只读接口返回类似于元组的对象，该对象有命名属性用于密码记录的标准字段。
| Index | Attribute | Meaning |
|---|---|---|
| 0 | pw_name | The user’s login name |
| 1 | pw_passwd | Encrypted password (optional) |
| 2 | pw_uid | User id (integer) |
| 3 | pw_gid | Group id (integer) |
| 4 | pw_gecos | Comment/full name |
| 5 | pw_dir | Home directory |
| 6 | pw_shell | Application started on login, usually a command interpreter |
Querying All Users
此示例打印系统上所有“real”（真实）用户的报告，包括其主目录（其中“real”定义为name不以“_”开头）。 要加载整个密码数据库，请使用getpwall（）。 返回值是具有未定义顺序的列表，因此需要在打印报表之前对其进行排序。
#pwd_getpwall.py
import pwd
import operator
# Load all of the user data, sorted by username
all_user_data = pwd.getpwall()
interesting_users = sorted(
(u for u in all_user_data if not u.pw_name.startswith('_')),
key=operator.attrgetter('pw_name')
)
# Find the longest lengths for a few fields
username_length = max(len(u.pw_name) for u in interesting_users) + 1
home_length = max(len(u.pw_dir) for u in interesting_users) + 1
uid_length = max(len(str(u.pw_uid)) for u in interesting_users) + 1
# Print report headers
fmt = ' '.join(['{:<{username_length}}',
'{:>{uid_length}}',
'{:<{home_length}}',
'{}'])
print(fmt.format('User',
'UID',
'Home Dir',
'Description',
username_length=username_length,
uid_length=uid_length,
home_length=home_length))
print('-' * username_length,
'-' * uid_length,
'-' * home_length,
'-' * 20)
# Print the data
for u in interesting_users:
print(fmt.format(u.pw_name,
u.pw_uid,
u.pw_dir,
u.pw_gecos,
username_length=username_length,
uid_length=uid_length,
home_length=home_length))
上面的大多数示例代码都可以很好地处理格式化结果。 最后的for循环显示了如何按名称访问记录中的字段。
$ python3 pwd_getpwall.py
User UID Home Dir Description
---------- ----------- ----------------- --------------------
Guest 201 /Users/Guest Guest User
daemon 1 /var/root System Services
daemon 1 /var/root System Services
dhellmann 501 /Users/dhellmann Doug Hellmann
nobody 4294967294 /var/empty Unprivileged User
nobody 4294967294 /var/empty Unprivileged User
root 0 /var/root System Administrator
root 0 /var/root System Administrator
Querying User By Name
要读取有关一个用户的信息，不必读取整个密码数据库。 使用getpwnam（），按名称检索有关用户的信息。
#pwd_getpwnam.py
import pwd
import sys
username = sys.argv[1]
user_info = pwd.getpwnam(username)
print('Username:', user_info.pw_name)
print('Password:', user_info.pw_passwd)
print('Comment :', user_info.pw_gecos)
print('UID/GID :', user_info.pw_uid, '/', user_info.pw_gid)
print('Home :', user_info.pw_dir)
print('Shell :', user_info.pw_shell)
运行此示例的系统上的密码存储在主用户数据库之外的影子文件中，因此密码字段在设置时将报告为全*。
$ python3 pwd_getpwnam.py dhellmann
Username: dhellmann
Password: ********
Comment : Doug Hellmann
UID/GID : 501 / 20
Home : /Users/dhellmann
Shell : /bin/bash
$ python3 pwd_getpwnam.py nobody
Username: nobody
Password: *
Comment : Unprivileged User
UID/GID : 4294967294 / 4294967294
Home : /var/empty
Shell : /usr/bin/false
Querying User By UID
还可以通过其数字用户ID查找用户。这对于查找文件的所有者很有用：
#pwd_getpwuid_fileowner.py
import pwd
import os
filename = 'pwd_getpwuid_fileowner.py'
stat_info = os.stat(filename)
owner = pwd.getpwuid(stat_info.st_uid).pw_name
print('{} is owned by {} ({})'.format(filename, owner, stat_info.st_uid))
$ python3 pwd_getpwuid_fileowner.py
pwd_getpwuid_fileowner.py is owned by dhellmann (501)
数字用户ID也可用于查找有关当前正在运行进程的用户的信息：
#pwd_getpwuid_process.py
import pwd
import os
uid = os.getuid()
user_info = pwd.getpwuid(uid)
print('Currently running with UID={} username={}'.format(uid, user_info.pw_name))
$ python3 pwd_getpwuid_process.py
Currently running with UID=501 username=dhellmann
grp — Unix Group Database
目的：从Unix group数据库中读取group数据。
grp模块可用于从组数据库（通常是/etc/group）中读取有关Unix组的信息。 只读接口返回类似于元组的对象，这些对象具有命名属性用于组记录的标准字段。
| Index | Attribute | Meaning |
|---|---|---|
| 0 | gr_name | Name |
| 1 | gr_passwd | Password, if any (encrypted) |
| 2 | gr_gid | Numerical id (integer) |
| 3 | gr_mem | Names of group members |
名称和密码值都是字符串，GID是整数，成员报告为字符串列表。
Querying All Groups
此示例打印系统上所有“真实”组的报告，包括其成员（其中“real”定义为名称不以“_”开头）。 要加载整个密码数据库，请使用getgrall（）。
#grp_getgrall.py
import grp
import textwrap
# Load all of the user data, sorted by username
all_groups = grp.getgrall()
interesting_groups = {
g.gr_name: g
for g in all_groups
if not g.gr_name.startswith('_')
}
print(len(interesting_groups.keys()))
# Find the longest length for a few fields
name_length = max(len(k) for k in interesting_groups) + 1
gid_length = max(len(str(u.gr_gid)) for u in interesting_groups.values()) + 1
# Set the members field width to avoid table columns wrapping
members_width = 19
# Print report headers
fmt = ' '.join(['{:<{name_length}}',
'{:{gid_length}}',
'{:<{members_width}}',
])
print(fmt.format('Name',
'GID',
'Members',
name_length=name_length,
gid_length=gid_length,
members_width=members_width))
print('-' * name_length,
'-' * gid_length,
'-' * members_width)
# Print the data
prefix = ' ' * (name_length + gid_length + 2)
for name, g in sorted(interesting_groups.items()):
# Format members to start in the column on the same line but
# wrap as needed with an indent sufficient to put the
# subsequent lines in the members column. The two indent
# prefixes need to be the same to compute the wrap properly,
# but the first should not be printed so strip it.
members = textwrap.fill(
', '.join(g.gr_mem),
initial_indent=prefix,
subsequent_indent=prefix,
width=members_width + len(prefix),
).strip()
print(fmt.format(g.gr_name,
g.gr_gid,
members,
name_length=name_length,
gid_length=gid_length,
members_width=members_width))
返回值是具有未定义顺序的列表，因此需要在打印报表之前对其进行排序。
$ python3 grp_getgrall.py
34
Name GID Members
------------------------------- ----------- -------------------
accessibility 90
admin 80 root
authedusers 50
bin 7
certusers 29 root, _jabber,
_postfix, _cyrus,
_calendar, _dovecot
com.apple.access_disabled 396
com.apple.access_ftp 395
com.apple.access_screensharing 398
com.apple.access_sessionkey 397
com.apple.access_ssh 399
com.apple.sharepoint.group.1 701 dhellmann
consoleusers 53
daemon 1 root
dialer 68
everyone 12
group 16
interactusers 51
kmem 2 root
localaccounts 61
mail 6 _teamsserver
netaccounts 62
netusers 52
network 69
nobody 4294967294
nogroup -1
operator 5 root
owner 10
procmod 9 root
procview 8 root
staff 20 root
sys 3 root
tty 4 root
utmp 45
wheel 0 root
Group Memberships for a User
另一个常见任务可能是打印给定用户的所有组的列表：
#grp_groups_for_user.py
import grp
username = 'dhellmann'
group_names = set(
g.gr_name
for g in grp.getgrall()
if username in g.gr_mem
)
print(username, 'belongs to:', ', '.join(sorted(group_names)))
唯一组名称集(set)在打印之前会进行排序。
$ python3 grp_groups_for_user.py
dhellmann belongs to: _appserveradm, _appserverusr, _lpadmin, admin, com.apple.sharepoint.group.1
Finding a Group By Name
与pwd一样，也可以通过名称或数字ID查询有关特定组的信息。
#grp_getgrnam.py
import grp
name = 'admin'
info = grp.getgrnam(name)
print('Name :', info.gr_name)
print('GID :', info.gr_gid)
print('Password:', info.gr_passwd)
print('Members :', ', '.join(info.gr_mem))
admin组有两个成员：
$ python3 grp_getgrnam.py
Name : admin
GID : 80
Password: *
Members : root, dhellmann
Finding a Group by ID
要识别运行当前进程的组，请将getgrgid（）与os.getgid（）结合使用。
#grp_getgrgid_process.py
import grp
import os
gid = os.getgid()
group_info = grp.getgrgid(gid)
print('Currently running with GID={} name={}'.format(gid, group_info.gr_name))
$ python3 grp_getgrgid_process.py
Currently running with GID=20 name=staff
要根据文件的权限获取组名，请查找os.stat（）返回的组。
#grp_getgrgid_fileowner.py
import grp
import os
filename = 'grp_getgrgid_fileowner.py'
stat_info = os.stat(filename)
owner = grp.getgrgid(stat_info.st_gid).gr_name
print('{} is owned by {} ({})'.format(filename, owner, stat_info.st_gid))
文件状态记录包括文件或目录的所有权和权限数据。
$ python3 grp_getgrgid_fileowner.py
grp_getgrgid_fileowner.py is owned by staff (20)