1. 背景

在看shell变量的时候引起了兴趣: 局部变量，全局变量，环境变量，shell的配置文件，参考博客:

http://c.biancheng.net/view/773.html

2. 交互式与非交互式

参考博客:

shell的两个属性:是否交互式(interactive), 是否登录(login) - 知乎 

man bash:

通常的理解是:

 man手册中给我们提供了怎么判断交互与非交互的方法:

 所以我看看我自己的shell是否是交互式的:

liaojunwu@liaojunwu-virtual-machine:~$ echo $PS1
\[\e]0;\u@\h: \w\a\]${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\$
liaojunwu@liaojunwu-virtual-machine:~$ 
liaojunwu@liaojunwu-virtual-machine:~$ echo $-
himBH
liaojunwu@liaojunwu-virtual-machine:~$ 

 3. 登录与非登陆

man bash:

通常的理解是:

 su和su -命令的区别参考博客: 一分钟知识点：linux命令之su 和 su - 

可以用shopt login_shell的方法来看看shell是否设置了login_shell选项，我看看我自己的shell:

liaojunwu@liaojunwu-virtual-machine:~$ shopt login_shell
login_shell    	off
liaojunwu@liaojunwu-virtual-machine:~$ 
liaojunwu@liaojunwu-virtual-machine:~$ su - liaojunwu --login
密码： 
liaojunwu@liaojunwu-virtual-machine:~$ 
liaojunwu@liaojunwu-virtual-machine:~$ 
liaojunwu@liaojunwu-virtual-machine:~$ shopt login_shell
login_shell    	on
liaojunwu@liaojunwu-virtual-machine:~$ 

 4. 为什么要知道这两种属性？

因为涉及到shell配置方式的不同，继续看man手册:

交互与登录属性一共有四种组合，我们只看三种:

登录交互与登录非交互: bash配置shell的顺序是:

/etc/profile->~/.bash_profile->~/.bash_login->~/.profile->~/.bashrc

展开/etc/profile又可以看到登录交互会去配置/etc/bash.bashrc

# /etc/profile: system-wide .profile file for the Bourne shell (sh(1))
# and Bourne compatible shells (bash(1), ksh(1), ash(1), ...).if [ "$PS1" ]; thenif [ "$BASH" ] && [ "$BASH" != "/bin/sh" ]; then# The file bash.bashrc already sets the default PS1.# PS1='\h:\w\$ 'if [ -f /etc/bash.bashrc ]; then. /etc/bash.bashrcfielseif [ "`id -u`" -eq 0 ]; thenPS1='# 'elsePS1='$ 'fifi
fiif [ -d /etc/profile.d ]; thenfor i in /etc/profile.d/*.sh; doif [ -r $i ]; then. $ifidoneunset i
fiexport PATH=$PATH:/usr/local/arm/gcc-linaro-4.9.4-2017.01-x86_64_arm-linux-gnueabihf/bin

非登录交互时: bash的配置顺序是:

/etc/bash.bashrc->~/.bashrc

我们可以看到不论是/etc/bash.bashrc还是~/.bashrc，都要求是交互模式才行:

 

 5. 验证

登录交互: /etc/profile->/etc/bash.bashrc->~/.bash_profile->~/.bash_login->~/.profile->~/.bashrc

liaojunwu@liaojunwu-virtual-machine:~$ 
liaojunwu@liaojunwu-virtual-machine:~$ echo $PS1
\[\e]0;\u@\h: \w\a\]${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\$
liaojunwu@liaojunwu-virtual-machine:~$ 
liaojunwu@liaojunwu-virtual-machine:~$ 
liaojunwu@liaojunwu-virtual-machine:~$ 
liaojunwu@liaojunwu-virtual-machine:~$ shopt login_shell
login_shell    	on
liaojunwu@liaojunwu-virtual-machine:~$ 
liaojunwu@liaojunwu-virtual-machine:~$ 
liaojunwu@liaojunwu-virtual-machine:~$ logout
liaojunwu@liaojunwu-virtual-machine:~$ exit
注销
liaojunwu@liaojunwu-virtual-machine:~$ exit
注销
liaojunwu@liaojunwu-virtual-machine:~$ exit
注销
liaojunwu@liaojunwu-virtual-machine:~$ su - root
密码： 
[DEBUG]in /etc/profile!
[DEBUG]in /etc/bash.bashrc!
root@liaojunwu-virtual-machine:~# 
root@liaojunwu-virtual-machine:~# 
root@liaojunwu-virtual-machine:~# su - liaojunwu --login
[DEBUG]in /etc/profile!
[DEBUG]in /etc/bash.bashrc!
[DEBUG]in ~./profile!
[DEBUG]in ~./bashrc !
liaojunwu@liaojunwu-virtual-machine:~$ 

非登录交互: /etc/bash.bashrc->~/.bashrc

[DEBUG]in /etc/bash.bashrc!
[DEBUG]in ~./bashrc !
liaojunwu@liaojunwu-virtual-machine:~$ echo $-
himBH
liaojunwu@liaojunwu-virtual-machine:~$ shopt login_shell
login_shell    	off
liaojunwu@liaojunwu-virtual-machine:~$ 
liaojunwu@liaojunwu-virtual-machine:~$ 
liaojunwu@liaojunwu-virtual-machine:~$ 
liaojunwu@liaojunwu-virtual-machine:~$ 
liaojunwu@liaojunwu-virtual-machine:~$ bash -i
[DEBUG]in /etc/bash.bashrc!
[DEBUG]in ~./bashrc !
liaojunwu@liaojunwu-virtual-machine:~$ 

6. PS1变量

参考博客: bash下变量PS1的完整理解_ps1变量_whowin的博客-CSDN博客