getent命令简述
getent - get entries（entry的复数，条目、项目、记载、记录）
getent命令可以用来察看系统的数据库中的相关记录
经常使用getent查看用户账号：
- 之前实验我们创建了一个UID为211的apahce系统账号，我们现在要查看apahce账号的信息
- 通常的做法是我们cat etc下的passwd得到账号apache信息
- 因为passwd也是系统的一种数据库，我们这时候就可以使用getent命令查看
[23:04:08 root@C8[ ~]#cat /etc/passwd | grep apahce
apahce:x:211:211:Apahce211:/var/www:/sbin/nologin
[23:04:14 root@C8[ ~]#getent passwd apahce
apahce:x:211:211:Apahce211:/var/www:/sbin/nologin
[22:57:00 root@C8[ ~]#getent --help
Usage: getent [OPTION...] database [key ...]
Get entries from administrative database.
-i, --no-idn disable IDN encoding
-s, --service=CONFIG Service configuration to be used
-?, --help Give this help list
--usage Give a short usage message
-V, --version Print program version
Mandatory or optional arguments to long options are also mandatory or optional
for any corresponding short options.
Supported databases:
ahosts ahostsv4 ahostsv6 aliases ethers group gshadow hosts initgroups
netgroup networks passwd protocols rpc services shadow
For bug reporting instructions, please see:
http://www.gnu.org/software/libc/bugs.html.
[23:04:48 root@C8[ ~]#man getent
GETENT(1) User Commands GETENT(1)
NAME
getent - get entries from Name Service Switch libraries
SYNOPSIS
getent [option]... database key...
DESCRIPTION
The getent command displays entries from databases supported by the Name Service Switch libraries, which are configured
in /etc/nsswitch.conf. If one or more key arguments are provided, then only the entries that match the supplied keys
will be displayed. Otherwise, if no key is provided, all entries will be displayed (unless the database does not sup‐
port enumeration).
The database may be any of those supported by the GNU C Library, listed below:
ahosts When no key is provided, use sethostent(3), gethostent(3), and endhostent(3) to enumerate the hosts data‐
base. This is identical to using hosts. When one or more key arguments are provided, pass each key in
succession to getaddrinfo(3) with the address family AF_UNSPEC, enumerating each socket address structure
returned.
ahostsv4 Same as ahosts, but use the address family AF_INET.
ahostsv6 Same as ahosts, but use the address family AF_INET6. The call to getaddrinfo(3) in this case includes the
AI_V4MAPPED flag.
aliases When no key is provided, use setaliasent(3), getaliasent(3), and endaliasent(3) to enumerate the aliases
database. When one or more key arguments are provided, pass each key in succession to getaliasbyname(3)
and display the result.
ethers When one or more key arguments are provided, pass each key in succession to ether_aton(3) and ether_host‐
ton(3) until a result is obtained, and display the result. Enumeration is not supported on ethers, so a
key must be provided.
group When no key is provided, use setgrent(3), getgrent(3), and endgrent(3) to enumerate the group database.
When one or more key arguments are provided, pass each numeric key to getgrgid(3) and each nonnumeric key
to getgrnam(3) and display the result.
gshadow When no key is provided, use setsgent(3), getsgent(3), and endsgent(3) to enumerate the gshadow database.
When one or more key arguments are provided, pass each key in succession to getsgnam(3) and display the
result.
hosts When no key is provided, use sethostent(3), gethostent(3), and endhostent(3) to enumerate the hosts data‐
base. When one or more key arguments are provided, pass each key to gethostbyaddr(3) or gethostby‐
name2(3), depending on whether a call to inet_pton(3) indicates that the key is an IPv6 or IPv4 address or
not, and display the result.
initgroups
When one or more key arguments are provided, pass each key in succession to getgrouplist(3) and display
the result. Enumeration is not supported on initgroups, so a key must be provided.
netgroup When one key is provided, pass the key to setnetgrent(3) and, using getnetgrent(3) display the resulting
string triple (hostname, username, domainname). Alternatively, three keys may be provided, which are
interpreted as the hostname, username and domainname to match to a netgroup name via innetgr(3). Enumera‐
tion is not supported on netgroup, so either one or three keys must be provided.
networks When no key is provided, use setnetent(3), getnetent(3), and endnetent(3) to enumerate the networks data‐
base. When one or more key arguments are provided, pass each numeric key to getnetbyaddr(3) and each non‐
numeric key to getnetbyname(3) and display the result.
passwd When no key is provided, use setpwent(3), getpwent(3), and endpwent(3) to enumerate the passwd database.
When one or more key arguments are provided, pass each numeric key to getpwuid(3) and each nonnumeric key
to getpwnam(3) and display the result.
protocols When no key is provided, use setprotoent(3), getprotoent(3), and endprotoent(3) to enumerate the protocols
database. When one or more key arguments are provided, pass each numeric key to getprotobynumber(3) and
each nonnumeric key to getprotobyname(3) and display the result.
rpc When no key is provided, use setrpcent(3), getrpcent(3), and endrpcent(3) to enumerate the rpc database.
When one or more key arguments are provided, pass each numeric key to getrpcbynumber(3) and each nonnu‐
meric key to getrpcbyname(3) and display the result.
services When no key is provided, use setservent(3), getservent(3), and endservent(3) to enumerate the services
database. When one or more key arguments are provided, pass each numeric key to getservbynumber(3) and
each nonnumeric key to getservbyname(3) and display the result.
shadow When no key is provided, use setspent(3), getspent(3), and endspent(3) to enumerate the shadow database.
When one or more key arguments are provided, pass each key in succession to getspnam(3) and display the
result.
OPTIONS
-s service, --service service
Override all databases with the specified service. (Since glibc 2.2.5.)
-s database:service, --service database:service
Override only specified databases with the specified service. The option may be used multiple times, but only
the last service for each database will be used. (Since glibc 2.4.)
-i, --no-idn
Disables IDN encoding in lookups for ahosts/getaddrinfo(3) (Since glibc-2.13.)
-?, --help
Print a usage summary and exit.
--usage
Print a short usage summary and exit.
-V, --version
Print the version number, license, and disclaimer of warranty for getent.
EXIT STATUS
One of the following exit values can be returned by getent:
0 Command completed successfully.
1 Missing arguments, or database unknown.
2 One or more supplied key could not be found in the database.
3 Enumeration not supported on this database.
SEE ALSO
nsswitch.conf(5)
COLOPHON
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Linux 2015-04-19