shell 环境变量

环境变量

• 特点
  • linux 系统创建
  • 大写
  • linux大部分地方都可以使用
• 查看所有环境变量
  • env
  • export
  • declare

#HISTSIZE    HISTFILESIZE 
[[e-mail] ~]# export HISTSIZE=10
 [[e-mail] ~]# history   
 991  echo "$PATH $(hostname) `whoami` {1..5}" 
 992  echo $PATH $(hostname) `whoami` {1..5} 
 993  echo $PATH $(hostname) `whoami` {1..5} *  
 994  env   
 995  export
 996  declare   
 997  export  TMOUT=3  
 998  history   
 999  export HISTSIZE=10 
 1000  history 
 
[[e-mail] ~]# export HISTFILESIZE=15 
[[e-mail] ~]# cat ~/.bash_history echo 
$_oldboy 
oldbing=666 
echo $oldbing
 oldbing=爱生活 爱冰冰 
 oldbing="爱生活 爱冰冰" 
 echo $oldbing
 cd 
 echo '$PATH $(hostname) `whoami` {1..5}'
 echo "$PATH $(hostname) `whoami` {1..5}"
 echo $PATH $(hostname) `whoami` {1..5}
 echo $PATH $(hostname) `whoami` {1..5} *
 env   export declare export  TMOUT=3

#HISTCONTROL 
[[e-mail] ~]# export HISTCONTROL=ignorespace 
[[e-mail] ~]# echo 654321 |passwd --stdin oldboy
 更改用户 oldboy 的密码 。
 passwd：所有的身份验证令牌已经成功更新。
 [[e-mail] ~]# 
 [[e-mail] ~]# 
 [[e-mail] ~]# 
 [[e-mail] ~]# 
 [[e-mail] ~]#    echo 111111  |passwd --stdin oldboy 
 更改用户 oldboy 的密码 。
 passwd：所有的身份验证令牌已经成功更新。
  [[e-mail] ~]# history  
  1003  ll -h ~/.bash_history  
  1004  less ~/.bash_history
  1005  export HISTFILESIZE=15 
  1006  cat ~/.bash_history  
  1007  cat -n  ~/.bash_history  
  1008  echo 123456 |passwd --stdin oldboy  
  1009  history  
  1010  export HISTCONTROL=ignorespace 
  1011  echo 654321 |passwd --stdin oldboy  
  1012  history 

#PROMPT_COMMAND
 
[[e-mail] ~]# export PROMPT_COMMAND="date"
 2020年 01月 08日 星期三 12:23:24 CST 
 [[e-mail] ~]# ls -l
 总用量 27408 
 drwxr-xr-x  3 root root     4096 12月 20 15:45 ansible_playbook 
 drwxr-xr-x  3 root root      133 12月 18 08:48 ansible-project1 
 drwxr-xr-x 15 root root      266 12月 24 10:22 ansible_role
 -rw-r--r--  1 root root 27998103 12月 23 12:39 ansible_role_2019-12-23.zip 
 drwxr-xr-x  2 root root     4096 12月 23 09:52 ansible_tasks 
 drwxr-xr-x  4 root root     4096 12月 20 15:59 ansible_variables 
 -rw-r--r--  1 root root    37621 12月 19 17:20 ansible_variableszip.zip 
 -rw-r--r--  1 root root      105 12月 23 11:43 sshkey.sh 
 -rw-r--r--  1 root root      610 12月 24 09:48 student.txt 

-rw-r--r--  1 root root      368 12月 24 09:49 yj.sh

**创建环境变量**
```bash
[[e-mail] ~]# oldboy=666 
[[e-mail] ~]# echo $oldboy 666
[[e-mail] ~]# env |grep oldboy 
[[e-mail] ~]# #export 变量  变量成为环境变量
[[e-mail] ~]# export oldboy=666 
[[e-mail] ~]# env |grep oldboy oldboy=666

环境变量相关的文件和目录

[[e-mail] ~]#cat /etc/profile.d/show.sh
#!/bin/bash
#author: oldboy
echo  oldboyedu.com

[[e-mail] ~]# head -2  /etc/profile /etc/bashrc   ~/.bashrc  ~/.bash_profile 
==> /etc/profile <== 
# /etc/profile 
echo  /etc/profile start
==> /etc/bashrc <==
 # /etc/bashrc 
 echo  /etc/bashrc  start
==> /root/.bashrc <==
 # .bashrc
==> /root/.bash_profile <== 
# .bash_profile
[[e-mail] ~]# tail  -1  /etc/profile /etc/bashrc   ~/.bashrc  ~/.bash_profile 
tail: 在未定义环境中的无效选项 -- 1 
[[e-mail] ~]# tail  -n1  /etc/profile /etc/bashrc   ~/.bashrc  ~/.bash_profile 
==> /etc/profile <== 
echo  /etc/profile end
==> /etc/bashrc <== 
echo   /etc/bashrc  end
==> /root/.bashrc <==
 echo   ~/.bashrc end
==> /root/.bash_profile <==
 echo     ~/.bash_profile end