系统管理老手教你小指的妙用

在我的系统管理员生涯中, 凭借着丰富的经验,我总结出了一些在命令行下提高效率的习惯.

其中两个习惯跟我的小指头有关，因为两个小指头一个按 [ENTER] 一个按 [TAB] 键.

Hit the enter key between every command

这个习惯很简单, 只是在命令与命令之间多按几次 [ENTER] 而已. 为什么要这样呢？看看下面两个终端大的输出就能理解了，这两个终端输入的命令都是一样的:

首先是没有 [ENTER] 的输出:

root@server:~# apt-get update
Hit:1 http://mirror.memset.com/ubuntu xenial InRelease
Get:2 http://mirror.memset.com/ubuntu xenial-updates InRelease [102 kB]
Get:3 http://mirror.memset.com/ubuntu xenial-security InRelease [102 kB]
Fetched 204 kB in 0s (433 kB/s)
Reading package lists... Done
root@server:~# apt-get upgrade
Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Done
The following packages have been kept back:
  libgl1-mesa-dri sysstat
0 upgraded, 0 newly installed, 0 to remove and 2 not upgraded.
root@server:~# apt-get install openvpn
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages were automatically installed and are no longer required:
  apache2-bin apache2-data apache2-utils libapr1 libaprutil1 libaprutil1-dbd-sqlite3 libaprutil1-ldap libgd3 libjbig0
  libjpeg-turbo8 libjpeg8 liblua5.1-0 libtiff5 libvpx3 libxslt1.1 nginx-common nginx-core
Use 'apt autoremove' to remove them.
Suggested packages:
  easy-rsa
The following NEW packages will be installed:
  openvpn
0 upgraded, 1 newly installed, 0 to remove and 2 not upgraded.
Need to get 0 B/421 kB of archives.
After this operation, 1026 kB of additional disk space will be used.
Preconfiguring packages ...
Selecting previously unselected package openvpn.
(Reading database ... 22196 files and directories currently installed.)
Preparing to unpack .../openvpn_2.3.10-1ubuntu2.1_amd64.deb ...
Unpacking openvpn (2.3.10-1ubuntu2.1) ...
Processing triggers for libc-bin (2.23-0ubuntu9) ...
Processing triggers for systemd (229-4ubuntu21) ...
Processing triggers for ureadahead (0.100.0-19) ...
Processing triggers for man-db (2.7.5-1) ...
Setting up openvpn (2.3.10-1ubuntu2.1) ...
Processing triggers for libc-bin (2.23-0ubuntu9) ...
root@server:~# cd /etc/openvpn/
root@server:/etc/openvpn# ls
update-resolv-conf

然后是, 带有 [ENTER] 的输出:

root@server:~#
root@server:~#
root@server:~# apt-get update
Hit:1 http://mirror.memset.com/ubuntu xenial InRelease
Get:2 http://mirror.memset.com/ubuntu xenial-updates InRelease [102 kB]
Get:3 http://mirror.memset.com/ubuntu xenial-security InRelease [102 kB]
Fetched 204 kB in 0s (433 kB/s)
Reading package lists... Done
root@server:~#
root@server:~#
root@server:~#
root@server:~# apt-get upgrade
Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Done
The following packages have been kept back:
  libgl1-mesa-dri sysstat
0 upgraded, 0 newly installed, 0 to remove and 2 not upgraded.
root@server:~#
root@server:~#
root@server:~#
root@server:~#
root@server:~# apt-get install openvpn
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages were automatically installed and are no longer required:
  apache2-bin apache2-data apache2-utils libapr1 libaprutil1 libaprutil1-dbd-sqlite3 libaprutil1-ldap libgd3 libjbig0
  libjpeg-turbo8 libjpeg8 liblua5.1-0 libtiff5 libvpx3 libxslt1.1 nginx-common nginx-core
Use 'apt autoremove' to remove them.
Suggested packages:
  easy-rsa
The following NEW packages will be installed:
  openvpn
0 upgraded, 1 newly installed, 0 to remove and 2 not upgraded.
Need to get 0 B/421 kB of archives.
After this operation, 1026 kB of additional disk space will be used.
Preconfiguring packages ...
Selecting previously unselected package openvpn.
(Reading database ... 22196 files and directories currently installed.)
Preparing to unpack .../openvpn_2.3.10-1ubuntu2.1_amd64.deb ...
Unpacking openvpn (2.3.10-1ubuntu2.1) ...
Processing triggers for libc-bin (2.23-0ubuntu9) ...
Processing triggers for systemd (229-4ubuntu21) ...
Processing triggers for ureadahead (0.100.0-19) ...
Processing triggers for man-db (2.7.5-1) ...
Setting up openvpn (2.3.10-1ubuntu2.1) ...
Processing triggers for libc-bin (2.23-0ubuntu9) ...
root@server:~#
root@server:~#
root@server:~# cd /etc/openvpn/
root@server:/etc/openvpn#
root@server:/etc/openvpn#
root@server:/etc/openvpn#
root@server:/etc/openvpn# ls
update-resolv-conf

很明显，使用空行分隔命令要容易阅读的多. 同样的, 当输出写满终端屏幕后，请不要用 clear 命令清理掉这些内容, 你应该让自己习惯在终端底部工作.

保留有输入过的命令及其输出和错误信息是一笔无可估量的财富,因为你可能会需要时常地返回来看之前做过了什么.

一旦你开始敲击回车,很快你就会在工作时不自觉地这么做.

Use Bash Complete For All The Things

Bash complete 是一个帮你补全命令名称，文件路径，文件名称以及命令选项的函数.

你应该尽可能的用它，它是命令行中节省时间的最大助力. 它不仅减少你打字的个数，而且减少了输错的可能性.

下面的例子假设你安装了 bash-completion:

Path completion

每个Linux系统管理员应该都听过并且使用过tab补全,但是大多数的管理员并没有发挥它的价值. 如果要算哪个功能用的最多的话(除了上面的Enter),那么tab补全是当之无愧的赢家. 它让我把 c d / v a r / w w w / m a g e n t o 简化成了 c d / v [TAB] w [TAB] m [TAB]

一些常用的地址，比如 /etc/, /home/, /var/log, 则变成肌肉记忆，能够快速进入.

记住, 如果按一次 [TAB] 不能立即得到正确的路径的话, 那么再按一下 [TAB] 会列出所有匹配的目录, 然后再多输入1到2个字符后，重新按tab进行补全. 假设我们有两个目录; /var/www/magento 和 /var/www/magellen, 要cd进入 /var/www/magento 可以这样:

root@server:~# cd /v[TAB] /w[TAB] /m[TAB] [TAB]

这一步会一直补全到两个目录不同的地方:

root@server:~# cd /var/www/mage

现在, 按两下[TAB], 可以看到所有匹配的目录, 然后输入你想要进入目录的第一个字符,比如 n, 在按一次 [TAB] 就会补全所有路径:

root@server:~# cd /var/www/m[TAB]
root@server:~# cd /var/www/mage[TAB][TAB]
magellen/ magento/
root@server:~# cd /var/www/magen[TAB]
root@server:~# cd /var/www/magento/[ENTER]
root@server:/var/www/magento#

File name completion

这是路径补全的一个简单扩展. Bash complete 会补全任何以你输入开头的文件名. 使用 Bash completion 可以减少输错的可能并且提高输入文件名的速度.

而且, 在只有一个文件或目录的情况下, Bash complete 会直接补全该文件名或目录而不用输入任何字符.

Command and command option completion

Bash complete 会检查并补全你 $PATH 中的所有命令. 如果你不记得了完整的命令，只需要i按下两次 [TAB] 就会看到所有匹配的命令了.

此外, 对于那些常见命令, Bash complete 还能为你补全参数选项.

比如, 使用命令 systemctl 重载 apache2.service 可以这样:

root@server:~# systemc[TAB] rel[TAB] apa[TAB]

这种方法可以将常用路径，常用命令变成肌肉记忆,使得它们的输入格外的快速.