bash-completion能提示命令、提示命令参数等，在CentOS7中，很多日常管理的命令格式较长如nmcli、ip、firewall-cmd、systemctl等，借助bash-completion可以快速、友好地学习新命令的使用。

最小化安装系统的时候默认不安装，由于软件在epel库中，安装时先安装epel-release.注意，安装完成后在新shell里生效，所以需要重连或创建新bash。

yum install epel-release -y
yum install bash-completion -y

如下，已经安装好的软件信息：

[root@localhost ~]# rpm -qi bash-completion 
Name       : bash-completion              Relocations: (not relocatable)
Version     : 1.3                          Vendor: Fedora Project
Release     : 7.el6                       Build Date: 2013年04月02日 星期二 23时00分20秒
Install Date: 2017年06月21日 星期三 09时46分44秒     Build Host: buildvm-02.phx2.fedoraproject.org
Group      : System Environment/Shells        Source RPM: bash-completion-1.3-7.el6.src.rpm
Size       : 590294                           License: GPLv2+
Signature   : RSA/8, 2013年04月03日 星期三 07时44分10秒, Key ID 3b49df2a0608b895
Packager    : Fedora Project
URL       : http://bash-completion.alioth.debian.org/
Summary     : Programmable completion for Bash
Description :
bash-completion is a collection of shell functions that take advantage of the programmable completion feature of bash.

使用TAB键补全命令、补全参数示范如下，CentOS7系统中命令的可读性强，参数和选项使用起来更友好：

#bash-completion功能示范，TAB键补齐常用命令参数选项                 
[root@localhost ~]# system
systemctl                       systemd-inhibit
systemd-analyze                 systemd-loginctl
systemd-ask-password            systemd-machine-id-setup
systemd-cat                     systemd-notify
systemd-cgls                    systemd-nspawn
systemd-cgtop                   systemd-path
systemd-coredumpctl             systemd-run
systemd-delta                   systemd-stdio-bridge
systemd-detect-virt             systemd-sysv-convert
systemd-escape                  systemd-tmpfiles
systemd-firstboot               systemd-tty-ask-password-agent
systemd-hwdb                    
[root@localhost ~]# systemctl 
add-requires           hybrid-sleep           reload-or-restart
add-wants              is-active              reload-or-try-restart
cancel                 is-enabled             rescue
cat                    is-failed              reset-failed
condreload             isolate                restart
condrestart            is-system-running      set-default
condstop               kexec                  set-environment
daemon-reexec          kill                   set-property
daemon-reload          link                   show
default                list-dependencies      show-environment
delete                 list-jobs              snapshot
disable                list-sockets           start
edit                   list-timers            status
emergency              list-unit-files        stop
enable                 list-units             suspend
exit                   mask                   switch-root
force-reload           poweroff               try-restart
get-default            preset                 unmask
halt                   reboot                 unset-environment
help                   reenable               
hibernate              reload                 
[root@localhost ~]# nmcli 
agent       device      help        networking  
connection  general     monitor     radio       
[root@localhost ~]# nmcli connection 
add      delete   edit     help     load     monitor  show     
clone    down     export   import   modify   reload   up       
[root@localhost ~]# nmcli connection edit 
con-name  ens192    id        type      
ens160    help      path      uuid      
[root@localhost ~]# nmcli connection add 
autoconnect                      ipv4.dns-priority
con-name                         ipv4.dns-search
connection.autoconnect           ipv4.gateway
connection.autoconnect-priority  ipv4.ignore-auto-dns
connection.autoconnect-slaves    ipv4.ignore-auto-routes
connection.gateway-ping-timeout  ipv4.may-fail
connection.id                    ipv4.method
connection.interface-name        ipv4.never-default
connection.lldp                  ipv4.route-metric
connection.master                ipv4.routes
connection.metered               ipv6.addresses
connection.permissions           ipv6.addr-gen-mode
connection.read-only             ipv6.dhcp-hostname
connection.secondaries           ipv6.dhcp-send-hostname
connection.slave-type            ipv6.dns
connection.stable-id             ipv6.dns-options
connection.timestamp             ipv6.dns-priority
connection.type                  ipv6.dns-search
connection.uuid                  ipv6.gateway
connection.zone                  ipv6.ignore-auto-dns
help                             ipv6.ignore-auto-routes
ifname                           ipv6.ip6-privacy
ipv4.addresses                   ipv6.may-fail
ipv4.dad-timeout                 ipv6.method
ipv4.dhcp-client-id              ipv6.never-default
ipv4.dhcp-fqdn                   ipv6.route-metric
ipv4.dhcp-hostname               ipv6.routes
--More--^C
[root@localhost ~]# firewall-cmd --
--add-forward-port=
--add-icmp-block=
--add-icmp-block-inversion
--add-interface=
--add-lockdown-whitelist-command=
--add-lockdown-whitelist-context=
--add-lockdown-whitelist-uid=
--add-lockdown-whitelist-user=
--add-masquerade
--add-port=
--add-protocol=
--add-rich-rule=
--add-service=
--add-source=
--add-source-port=
--change-interface=
--change-source=
--change-zone=
--complete-reload
--direct
--get-active-zones
--get-default-zone
--get-icmptypes
--get-ipset-types
--get-log-denied
--get-services
--get-zone-of-interface=
--get-zones
--help
--info-icmptype
--info-ipset
--info-service
--info-zone
--More--
[root@localhost ~]# firewall-cmd --

linux命令补全参数提示程序bash-completion