Operation and Maintenance
Linux Operation and Maintenance
Linux environment variable configuration summary
Linux environment variable configuration summary
export PATH
vim ~/.bashrc
vim ~/.bash_profile
vim /etc/bashrc
vim /etc/profile
vim /etc/environment
export命令显示当前系统定义的所有环境变量echo $PATH命令输出当前的PATH环境变量 的值这两个命令执行的效果如下uusama@ubuntu:~$ exportdeclare -x HOME="/home/uusama"declare -x LANG="en_US.UTF-8"declare -x LANGUAGE="en_US:"declare -x LESSCLOSE="/usr/bin/lesspipe %s %s"declare -x LESSOPEN="| /usr/bin/lesspipe %s"declare -x LOGNAME="uusama"declare -x MAIL="/var/mail/uusama"declare -x PATH="/home/uusama/bin:/home/uusama/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"declare -x SSH_TTY="/dev/pts/0"declare -x TERM="xterm"declare -x USER="uusama"uusama@ubuntu:~$ echo $PATH/home/uusama/bin:/home/uusama/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin 其中PATH变量定义了运行命令的查找路径,以冒号:分割不同的路径,使用export定义的时候可加双引号也可不加。推荐下自己做的 Spring Cloud 的实战项目:https://github.com/YunaiV/onemall03、Linux环境变量配置方法一:export PATH使用export命令直接修改PATH的值,配置MySQL进入环境变量的方法:export PATH=/home/uusama/mysql/bin:$PATH# 或者把PATH放在前面export PATH=$PATH:/home/uusama/mysql/bin 注意事项:生效时间:立即生效生效期限:当前终端有效,窗口关闭后无效生效范围:仅对当前用户有效配置的环境变量 中不要忘了加上原来的配置,即$PATH部分,避免覆盖原来配置04、Linux环境变量配置方法二:vim ~/.bashrc通过修改用户目录下的~/.bashrc文件进行配置:vim ~/.bashrc# 在最后一行加上export PATH=$PATH:/home/uusama/mysql/bin 注意事项:生效时间:使用相同的用户打开新的终端时生效,或者手动source ~/.bashrc生效生效期限:永久有效生效范围:仅对当前用户有效如果有后续的环境变量加载文件覆盖了PATH定义,则可能不生效05、Linux环境变量配置方法三:vim ~/.bash_profile和修改~/.bashrc文件类似,也是要在文件最后加上新的路径即可:vim ~/.bash_profile# 在最后一行加上export PATH=$PATH:/home/uusama/mysql/bin 注意事项:生效时间:使用相同的用户打开新的终端时生效,或者手动source ~/.bash_profile生效生效期限:永久有效生效范围:仅对当前用户有效如果没有~/.bash_profile文件,则可以编辑~/.profile文件或者新建一个06、Linux环境变量配置方法四:vim /etc/bashrc该方法是修改系统配置,需要管理员权限(如root)或者对该文件的写入权限:# 如果/etc/bashrc文件不可编辑,需要修改为可编辑chmod -v u+w /etc/bashrcvim /etc/bashrc# 在最后一行加上export PATH=$PATH:/home/uusama/mysql/bin 注意事项:生效时间:新开终端生效,或者手动source /etc/bashrc生效生效期限:永久有效生效范围:对所有用户有效07、Linux环境变量配置方法五:vim /etc/profile该方法修改系统配置,需要管理员权限或者对该文件的写入权限,和vim /etc/bashrc类似:# 如果/etc/profile文件不可编辑,需要修改为可编辑chmod -v u+w /etc/profilevim /etc/profile# 在最后一行加上export PATH=$PATH:/home/uusama/mysql/bin 注意事项:生效时间:新开终端生效,或者手动source /etc/profile生效生效期限:永久有效生效范围:对所有用户有效另外搜索公众号Linux中文社区回复关键字"私房菜”获取一份惊喜礼包。 08、Linux环境变量配置方法六:vim /etc/environment该方法是修改系统环境配置文件,需要管理员权限或者对该文件的写入权限:# 如果/etc/bashrc文件不可编辑,需要修改为可编辑chmod -v u+w /etc/environmentvim /etc/profile# 在最后一行加上export PATH=$PATH:/home/uusama/mysql/bin 注意事项:生效时间:新开终端生效,或者手动source /etc/environment生效生效期限:永久有效生效范围:对所有用户有效09、Linux环境变量加载原理解析上面列出了环境变量的各种配置方法,那么Linux是如何加载这些配置的呢?是以什么样的顺序加载的呢?特定的加载顺序会导致相同名称的环境变量 定义被覆盖或者不生效。10、环境变量的分类环境变量可以简单的分成用户自定义的环境变量以及系统级别的环境变量。用户级别环境变量 定义文件:~/.bashrc、~/.profile(部分系统为:~/.bash_profile)系统级别环境变量 定义文件:/etc/bashrc、/etc/profile(部分系统为:/etc/bash_profile)、/etc/environment
In addition, in the user environment variables, the system will first read the ~/.bash_profile (or ~/.profile) file, if there is no such file, it will read~/.bash_login, and then read ~/.bashrc based on the contents of these files.
11. Method for testing the loading order of Linux environment variables
In order to test the environment variable loading order of different files, we set the load order of each environment variable The first line in the definition file all defines the same environment variable UU_ORDER. The value of this variable is its own value connected to the current file name.
The files that need to be modified are as follows:
/etc/environment
/etc/profile
/etc/profile.d/test.sh,新建文件,没有文件夹可略过/etc/bashrc,或者/etc/bash.bashrc
~/.bash_profile,或者~/.profile
~/.bashrc
在每个文件中的第一行都加上下面这句代码,并相应的把冒号后的内容修改为当前文件的绝对文件名。
export UU_ORDER="$UU_ORDER:~/.bash_profile"
修改完之后保存,新开一个窗口,然后echo $UU_ORDER观察变量的值:
uusama@ubuntu:~$ echo $UU_ORDER$UU_ORDER:/etc/environment:/etc/profile:/etc/bash.bashrc:/etc/profile.d/test.sh:~/.profile:~/.bashrc
可以推测出Linux加载环境变量的顺序如下:
/etc/environment
/etc/profile
/etc/bash.bashrc
/etc/profile.d/test.sh
~/.profile
~/.bashrc
12、Linux环境变量文件加载详解
由上面的测试可容易得出Linux加载环境变量 的顺序如下,:
系统环境变量 -> 用户自定义环境变量/etc/environment -> /etc/profile -> ~/.profile
打开/etc/profile文件你会发现,该文件的代码中会加载/etc/bash.bashrc文件,然后检查/etc/profile.d/目录下的.sh文件并加载。
# /etc/profile: system-wide .profile file for the Bourne shell (sh(1))# and Bourne compatible shells (bash(1), ksh(1), ash(1), ...).if [ "$PS1" ]; then if [ "$BASH" ] && [ "$BASH" != "/bin/sh" ]; then # The file bash.bashrc already sets the default PS1. # PS1='\h:\w\$ ' if [ -f /etc/bash.bashrc ]; then . /etc/bash.bashrc fi else if [ "`id -u`" -eq 0 ]; then PS1='# ' else PS1='$ ' fi fifiif [ -d /etc/profile.d ]; then for i in /etc/profile.d/*.sh; do if [ -r $i ]; then . $i fi done unset ifi
其次再打开~/.profile文件,会发现该文件中加载了~/.bashrc文件。
# if running bashif [ -n "$BASH_VERSION" ]; then # include .bashrc if it exists if [ -f "$HOME/.bashrc" ]; then . "$HOME/.bashrc" fifi# set PATH so it includes user's private bin directoriesPATH="$HOME/bin:$HOME/.local/bin:$PATH"
从~/.profile文件中代码不难发现,/.profile文件只在用户登录的时候读取一次 ,而/.bashrc会在每次运行Shell脚本的时候读取一次。
13、一些小技巧
可以自定义一个环境变量 文件,比如在某个项目下定义uusama.profile,在这个文件中使用export定义一系列变量,然后在~/.profile文件后面加上:sourc uusama.profile,这样你每次登陆都可以在Shell脚本中使用自己定义的一系列变量。
也可以使用alias命令定义一些命令的别名,比如alias rm="rm -i"(双引号必须),并把这个代码加入到~/.profile中,这样你每次使用rm命令的时候,都相当于使用rm -i命令,非常方便。
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