【CentOS 7笔记34】，shell变量和环境变量配置文件#

shallow丿ove

---

变量

环境变量

[root@localhost ~]# echo $PATH
	/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/root/bin
[root@localhost ~]# echo $LANG
	en_US.UTF-8

[root@localhost ~]# env
	XDG_SESSION_ID=8
	HOSTNAME=localhost.localdomain
	SELINUX_ROLE_REQUESTED=
	TERM=xterm
	SHELL=/bin/bash
	HISTSIZE=5000
	SSH_CLIENT=192.168.9.1 2272 22
	SELINUX_USE_CURRENT_RANGE=
	SSH_TTY=/dev/pts/0
	USER=root
	LS_COLORS=rs=0:di=01;34:ln=01;36:mh=00:pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:or=40;31;01:mi=01;05;37;41:su=37;41:sg=30;43:ca=30;41:tw=30;42:ow=34;42:st=37;44:ex=01;32:*.tar=01;31:*.tgz=01;31:*.arc=01;31:*.arj=01;31:*.taz=01;31:*.lha=01;31:*.lz4=01;31:*.lzh=01;31:*.lzma=01;31:*.tlz=01;31:*.txz=01;31:*.tzo=01;31:*.t7z=01;31:*.zip=01;31:*.z=01;31:*.Z=01;31:*.dz=01;31:*.gz=01;31:*.lrz=01;31:*.lz=01;31:*.lzo=01;31:*.xz=01;31:*.bz2=01;31:*.bz=01;31:*.tbz=01;31:*.tbz2=01;31:*.tz=01;31:*.deb=01;31:*.rpm=01;31:*.jar=01;31:*.war=01;31:*.ear=01;31:*.sar=01;31:*.rar=01;31:*.alz=01;31:*.ace=01;31:*.zoo=01;31:*.cpio=01;31:*.7z=01;31:*.rz=01;31:*.cab=01;31:*.jpg=01;35:*.jpeg=01;35:*.gif=01;35:*.bmp=01;35:*.pbm=01;35:*.pgm=01;35:*.ppm=01;35:*.tga=01;35:*.xbm=01;35:*.xpm=01;35:*.tif=01;35:*.tiff=01;35:*.png=01;35:*.svg=01;35:*.svgz=01;35:*.mng=01;35:*.pcx=01;35:*.mov=01;35:*.mpg=01;35:*.mpeg=01;35:*.m2v=01;35:*.mkv=01;35:*.webm=01;35:*.ogm=01;35:*.mp4=01;35:*.m4v=01;35:*.mp4v=01;35:*.vob=01;35:*.qt=01;35:*.nuv=01;35:*.wmv=01;35:*.asf=01;35:*.rm=01;35:*.rmvb=01;35:*.flc=01;35:*.avi=01;35:*.fli=01;35:*.flv=01;35:*.gl=01;35:*.dl=01;35:*.xcf=01;35:*.xwd=01;35:*.yuv=01;35:*.cgm=01;35:*.emf=01;35:*.axv=01;35:*.anx=01;35:*.ogv=01;35:*.ogx=01;35:*.aac=01;36:*.au=01;36:*.flac=01;36:*.mid=01;36:*.midi=01;36:*.mka=01;36:*.mp3=01;36:*.mpc=01;36:*.ogg=01;36:*.ra=01;36:*.wav=01;36:*.axa=01;36:*.oga=01;36:*.spx=01;36:*.xspf=01;36:
	MAIL=/var/spool/mail/root
	PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/root/bin
	PWD=/root
	LANG=en_US.UTF-8
	SELINUX_LEVEL_REQUESTED=
	HISTCONTROL=ignoredups
	SHLVL=1
	HOME=/root
	LOGNAME=root
	SSH_CONNECTION=192.168.9.1 2272 192.168.9.134 22
	LESSOPEN=||/usr/bin/lesspipe.sh %s
	XDG_RUNTIME_DIR=/run/user/0
	_=/usr/bin/env
[root@localhost ~]# set	#set查看系统和用户自定义变量
	#系统和用户自定义变量

自定义变量

• 自定义变量a=1
• 变量名规则：字母、数字下划线，首位不能为数字
• 变量值有特殊符号时须要用单引号括起来
• 变量的累加
• 全局变量export b=2
• unset变量

[root@localhost ~]# a=111
[root@localhost ~]# echo $a
	111
[root@localhost ~]# set | grep 111
	_=111
	a=111

[root@localhost ~]# a="'a b c'"
[root@localhost ~]# echo $a
	'a b c'
[root@localhost ~]# a='"a b c"'
[root@localhost ~]# echo $a
	"a b c"

[root@localhost ~]# a="a$bc"
[root@localhost ~]# echo $a
	a
[root@localhost ~]# a='a$bc'
[root@localhost ~]# echo $a
	a$bc

[root@localhost ~]# a=1
[root@localhost ~]# b=2
[root@localhost ~]# echo $a$b
	12

[root@localhost ~]# c='a$bc'
[root@localhost ~]# echo $c
	a$bc
[root@localhost ~]# c=a$bc
[root@localhost ~]# echo $c
	a
[root@localhost ~]# c="a$b"c
[root@localhost ~]# echo $c
	a2c

本地变量

[root@localhost ~]# w
	 15:49:26 up  8:38,  2 users,  load average: 0.00, 0.01, 0.05
	USER     TTY        LOGIN@   IDLE   JCPU   PCPU WHAT
	root     pts/0     13:01    6.00s  0.45s  0.00s w
	root     pts/1     15:49    6.00s  0.02s  0.02s -bash
[root@localhost ~]# echo $SSH_TTY
	/dev/pts/0

打开另外一个终端

[root@localhost ~]# w
	 15:49:12 up  8:37,  2 users,  load average: 0.00, 0.01, 0.05
	USER     TTY        LOGIN@   IDLE   JCPU   PCPU WHAT
	root     pts/0     13:01   32.00s  0.45s  0.45s -bash
	root     pts/1     15:49    0.00s  0.03s  0.01s w
[root@localhost ~]# echo $SSH_TTY
	/dev/pts/1

[root@localhost ~]# hello=world
[root@localhost ~]# echo $hello
	world

打开另外一个终端

[root@localhost ~]# echo $hello

返回原来的终端下，打开一个bash

[root@localhost ~]# bash
[root@localhost ~]# pstree
	bash: pstree: command not found

[root@localhost ~]# yum provides "/*/pstree"
	Loaded plugins: fastestmirror
	Loading mirror speeds from cached hostfile
	 * epel: mirrors.ustc.edu.cn
	epel/x86_64/filelists_db                                                    | 9.8 MB  00:00:11     
	extras/7/x86_64/filelists_db                                                | 494 kB  00:00:01     
	psmisc-22.20-15.el7.x86_64 : Utilities for managing processes on your system
	Repo        : base
	Matched from:
	Filename    : /usr/bin/pstree

[root@localhost ~]# yum install -y psmisc
	Loaded plugins: fastestmirror
	base                                                                        | 3.6 kB  00:00:00     
	epel/x86_64/metalink                                                        | 6.3 kB  00:00:00     
	extras                                                                      | 3.4 kB  00:00:00     
	updates                                                                     | 3.4 kB  00:00:00     
	updates/7/x86_64/primary_db                                                 | 3.6 MB  00:00:03     
	Loading mirror speeds from cached hostfile
	 * epel: mirrors.ustc.edu.cn
	Resolving Dependencies
	--> Running transaction check
	---> Package psmisc.x86_64 0:22.20-15.el7 will be installed
	--> Finished Dependency Resolution

	Dependencies Resolved

	===================================================================================================
	 Package               Arch                  Version                     Repository           Size
	===================================================================================================
	Installing:
	 psmisc                x86_64                22.20-15.el7                base                141 k

	Transaction Summary
	===================================================================================================
	Install  1 Package

	Total download size: 141 k
	Installed size: 475 k
	Downloading packages:
	psmisc-22.20-15.el7.x86_64.rpm                                              | 141 kB  00:00:00     
	Running transaction check
	Running transaction test
	Transaction test succeeded
	Running transaction
	  Installing : psmisc-22.20-15.el7.x86_64                                                      1/1 
	  Verifying  : psmisc-22.20-15.el7.x86_64                                                      1/1 

	Installed:
	  psmisc.x86_64 0:22.20-15.el7                                                                     

	Complete!

[root@localhost ~]# pstree
	systemd─┬─NetworkManager───2*[{NetworkManager}]
			├─agetty
			├─auditd───{auditd}
			├─avahi-daemon───avahi-daemon
			├─crond
			├─dbus-daemon───{dbus-daemon}
			├─firewalld───{firewalld}
			├─iprdump
			├─iprinit
			├─iprupdate
			├─lvmetad
			├─master─┬─pickup
			│        └─qmgr
			├─polkitd───5*[{polkitd}]
			├─rsyslogd───2*[{rsyslogd}]
			├─sshd─┬─sshd───bash───bash───pstree
			│      └─sshd───bash
			├─systemd-journal
			├─systemd-logind
			├─systemd-udevd
			└─tuned───4*[{tuned}]

这里咱们经过├─sshd─┬─sshd───bash───bash───pstree能够看到，咱们sshd远程登陆得到了一个bash，经过bash上面打开了一个子shell，经过这个bash咱们又运行了pstree这个进程

[root@localhost ~]# echo $hello

[root@localhost ~]# exit
	exit
[root@localhost ~]# pstree
	systemd─┬─NetworkManager───2*[{NetworkManager}]
			├─agetty
			├─auditd───{auditd}
			├─avahi-daemon───avahi-daemon
			├─crond
			├─dbus-daemon───{dbus-daemon}
			├─firewalld───{firewalld}
			├─iprdump
			├─iprinit
			├─iprupdate
			├─lvmetad
			├─master─┬─pickup
			│        └─qmgr
			├─polkitd───5*[{polkitd}]
			├─rsyslogd───2*[{rsyslogd}]
			├─sshd─┬─sshd───bash───pstree
			│      └─sshd───bash
			├─systemd-journal
			├─systemd-logind
			├─systemd-udevd
			└─tuned───4*[{tuned}]
[root@localhost ~]# echo $hello
	world

全局变量export

[root@localhost ~]# export hello=world
[root@localhost ~]# echo $hello
	world
[root@localhost ~]# bash
[root@localhost ~]# echo $hello
	world
[root@localhost ~]# bash
[root@localhost ~]# echo $hello
	world

打开另外一个终端

[root@localhost ~]# pstree
	systemd─┬─NetworkManager───2*[{NetworkManager}]
			├─agetty
			├─auditd───{auditd}
			├─avahi-daemon───avahi-daemon
			├─crond
			├─dbus-daemon───{dbus-daemon}
			├─firewalld───{firewalld}
			├─iprdump
			├─iprinit
			├─iprupdate
			├─lvmetad
			├─master─┬─pickup
			│        └─qmgr
			├─polkitd───5*[{polkitd}]
			├─rsyslogd───2*[{rsyslogd}]
			├─sshd─┬─sshd───bash───bash───bash
			│      └─sshd───bash───pstree
			├─systemd-journal
			├─systemd-logind
			├─systemd-udevd
			└─tuned───4*[{tuned}]
[root@localhost ~]# echo $hello

这是由于两个终端都不属于同一个sshd，他们区别开来，并不冲突

返回原来的终端

[root@localhost ~]# export a=123
[root@localhost ~]# echo $a
123
[root@localhost ~]# exit
exit
[root@localhost ~]# echo $a

取消变量值unset

[root@localhost ~]# echo $hello
world
[root@localhost ~]# unset hello
[root@localhost ~]# echo $hello

不一样用户登陆，全局变量只对当前用户的shell和子shell生效，若要其余用户生效则能够到/etc/profile进行修改配置

环境变量配置文件

• /etc/profile用户环境变量，交互，登陆才执行
• /etc/bashrc用户不用登陆，执行shell就生效

当前用户下的目录

• ~/.bashrc
• ~/.bash_profile
• ~/.bash_history
• ~/.bash_logout

[root@localhost ~]# vi .bash_profile
	# .bash_profile

	# Get the aliases and functions
	if [ -f ~/.bashrc ]; then
			. ~/.bashrc
	fi

	# User specific environment and startup programs

	PATH=$PATH:$HOME/bin

	export PATH

. ~/.bashrc与source ~/.bashrc的做用是同样的，加载配置文件

[root@localhost ~]# vi .bashrc
	# .bashrc

	# User specific aliases and functions

	alias rm='rm -i'
	alias cp='cp -i'
	alias mv='mv -i'

	# Source global definitions
	if [ -f /etc/bashrc ]; then
			. /etc/bashrc
	fi

[root@localhost ~]# vi /etc/bashrc
/PS1
	[ "$PS1" = "\\s-\\v\\\$ " ] && PS1="[\u@\h \W]\\$ "
[root@localhost ~]#cd /etc/sysconfig/network-scripts/
[root@localhost /network-scripts]## echo $PS1
	[\u@\h \W]\$

这里PS1的u表示当前用户，h为主机名，W为绝对路径最后一个目录

[root@localhost ~]# PS1='[\u@\h \w]\$'
[root@localhost ~]# cd /etc/sysconfig/network-scripts/
[root@localhost /etc/sysconfig/network-scripts]#
[root@localhost /etc/sysconfig/network-scripts]# PS1='\u@\h \w\$'
root@localhost /etc/sysconfig/network-scripts#
root@localhost /etc/sysconfig/network-scripts# PS1='<\u@\h \w>\$'
<root@localhost /etc/sysconfig/network-scripts>#

甚至还能够带颜色显示

root@localhost:/etc/sysconfig/network-scripts# PS1='[\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;36m\]\w\[\033[00m\]]\$'
[root@localhost:/etc/sysconfig/network-scripts]#

有PS1，那么也有PS2，而PS2如运行mysql等程序时，则会进入PS2界面

[root@localhost:~]# echo $PS2
	>
[root@localhost:~]# for i in `seq 1 10`
	> do
	> echo $i
	> done
	1
	2
	3
	4
	5
	6
	7
	8
	9
	10
[root@localhost:~]# for i in `seq 1 10`; do echo $i; done
	1
	2
	3
	4
	5
	6
	7
	8
	9
	10
[root@localhost:~]# PS2="#"
[root@localhost:~]# echo $PS2
	#
[root@localhost:~]# for i in `seq 1 10`
	#do
	#echo $i
	#done
	1
	2
	3
	4
	5
	6
	7
	8
	9
	10