一、命令行展开
~ : 自动展开为用户的主目录，或指定的用户的主目录 ；
{}: 可承载一个以逗号分隔的路径列表，并能够将其展开为多个路径；
eg.
创建目录 /tmp/x , /tmp/x/y1 , /tmp/x/y2 , /tmp/x/y1/a , /tmp/x/y1/b
[root@localhost ~]# mkdir -pv /tmp/x/{y1/{a,b},y2}
mkdir: created directory ‘/tmp/x’
mkdir: created directory ‘/tmp/x/y1’
mkdir: created directory ‘/tmp/x/y1/a’
mkdir: created directory ‘/tmp/x/y1/b’
mkdir: created directory ‘/tmp/x/y2’
[root@localhost ~]# tree /tmp/x
/tmp/x
├── y1
│ ├── a
│ └── b
└── y2
4 directories, 0 files
[root@localhost ~]#
[root@localhost ~]# mkdir -v {a,c}_{b,d}
mkdir: created directory ‘a_b’
mkdir: created directory ‘a_d’
mkdir: created directory ‘c_b’
mkdir: created directory ‘c_d’
[root@localhost ~]#
创建如下结构的目录：
[root@localhost ~]# tree /tmp/mysysroot
/tmp/mysysroot
├── bin
├── etc
│ └── sysconfig
│ └── network-scripts
├── sbin
├── usr
│ ├── bin
│ ├── lib
│ ├── lib64
│ ├── local
│ │ ├── bin
│ │ ├── etc
│ │ ├── lib
│ │ └── sbin
│ └── sbin
└── var
├── cache
├── log
└── run
19 directories, 0 files
[root@localhost ~]#
创建过程如下：
[root@localhost ~]# mkdir -pv /tmp/mysysroot/{bin,sbin,etc/sysconfig/network-scripts,usr/{bin,sbin,local/{bin,sbin,etc,lib},lib,lib64},var/{cache,log,run}}
mkdir: created directory ‘/tmp/mysysroot’
mkdir: created directory ‘/tmp/mysysroot/bin’
mkdir: created directory ‘/tmp/mysysroot/sbin’
mkdir: created directory ‘/tmp/mysysroot/etc’
mkdir: created directory ‘/tmp/mysysroot/etc/sysconfig’
mkdir: created directory ‘/tmp/mysysroot/etc/sysconfig/network-scripts’
mkdir: created directory ‘/tmp/mysysroot/usr’
mkdir: created directory ‘/tmp/mysysroot/usr/bin’
mkdir: created directory ‘/tmp/mysysroot/usr/sbin’
mkdir: created directory ‘/tmp/mysysroot/usr/local’
mkdir: created directory ‘/tmp/mysysroot/usr/local/bin’
mkdir: created directory ‘/tmp/mysysroot/usr/local/sbin’
mkdir: created directory ‘/tmp/mysysroot/usr/local/etc’
mkdir: created directory ‘/tmp/mysysroot/usr/local/lib’
mkdir: created directory ‘/tmp/mysysroot/usr/lib’
mkdir: created directory ‘/tmp/mysysroot/usr/lib64’
mkdir: created directory ‘/tmp/mysysroot/var’
mkdir: created directory ‘/tmp/mysysroot/var/cache’
mkdir: created directory ‘/tmp/mysysroot/var/log’
mkdir: created directory ‘/tmp/mysysroot/var/run’
tree – list contents of directories in a tree-like format.
tree [-acdfghilnpqrstuvxACDFQNSUX] [-L level [-R]] [-H baseHREF] [-T title] [-o filename] [–nolinks]
[-P pattern] [-I pattern] [–inodes] [–device] [–noreport] [–dirsfirst] [–version] [–help]
[–filelimit #] [–si] [–prune] [–du] [–timefmt format] [directory …]
OPTION:
-L level : 指定要显示的层级；不指定，则默认显示所有目录层级；
eg.
列出 /etc 目录下的2层结构树：
[root@localhost ~]# tree -L 2 /etc
/etc
├── adjtime
├── aliases
├── aliases.db
├── alternatives
│ ├── ld -> /usr/bin/ld.bfd
│ ├── libnssckbi.so.x86_64 -> /usr/lib64/pkcs11/p11-kit-trust.so
│ ├── mta -> /usr/sbin/sendmail.postfix
│ ├── mta-aliasesman -> /usr/share/man/man5/aliases.postfix.5.gz
│ ├── mta-mailq -> /usr/bin/mailq.postfix
│ ├── mta-mailqman -> /usr/share/man/man1/mailq.postfix.1.gz
│ ├── mta-newaliases -> /usr/bin/newaliases.postfix
│ ├── mta-newaliasesman -> /usr/share/man/man1/newaliases.postfix.1.gz
│ ├── mta-pam -> /etc/pam.d/smtp.postfix
│ ├── mta-rmail -> /usr/bin/rmail.postfix
.......
├── anacrontab
├── asound.conf
├── at.deny
├── audisp
│ ├── audispd.conf
│ └── plugins.d
├── audit
│ ├── auditd.conf
│ ├── audit.rules
│ ├── audit-stop.rules
│ └── rules.d
.......
├── yum.conf
└── yum.repos.d
├── CentOS-Base.repo
├── CentOS-CR.repo
├── CentOS-Debuginfo.repo
├── CentOS-fasttrack.repo
├── CentOS-Media.repo
├── CentOS-Sources.repo
├── CentOS-Vault.repo
├── epel.repo
└── epel-testing.repo
172 directories, 372 files
[root@localhost ~]#
二、命令的执行状态结果
1、命令执行的状态结果，bash通过状态返回值来输出此结果；
>> 成功 ： 0
>> 失败 ： 1-255
2、命令执行完成后，其状态返回值保存于bash的特殊变量 $? 中；
eg. [root@localhost ~]# cd /etc [root@localhost etc]# echo $? 0 [root@localhost etc]# cddd /etc -bash: cddd: command not found [root@localhost etc]# echo $? 127 [root@localhost etc]# cd /etttt -bash: cd: /etttt: No such file or directory [root@localhost etc]# echo $? 1 [root@localhost etc]#
PS : 注意区分命令执行结果与命令执行的状态结果2者的区别
> 命令正常执行后，有的还返回有命令执行结果，即命令返回值；
> 根据命令及其功能不同，命令的执行结果各不相同；
[root@localhost ~]# ls a_b anaconda-ks.cfg c_d nginx-1.12.2.tar.gz php-7.0.26.tar.bz2 a_d c_b mysql-boost-5.7.20.tar.gz pcre-8.41.tar.bz2 [root@localhost ~]# echo $? 0 [root@localhost ~]#
3、引用命令的执行结果
> $(COMMAND)
> `COMMAND`
~]# mkdir $(date +%H-%M-%S)
~]# ABC=`date +%H-%M-%S`
三、引用
> 强引用 ： ” 不做变量的替换；
> 弱引用 ： “” 做变量替换，引用变量的值；
> 命令引用： “ 反引号；
四、快捷键
> Ctrl + a : 跳转至命令行行首
> Ctrl + e : 跳转至命令行行尾
> Ctrl + u : 删除行首至光标所在处之间的所有字符；
> Ctrl + k : 删除光标所在处至行尾的所有字符；
> Ctrl + l : 清屏，相当于 clear ;