Mac系统的环境变量，加载顺序为：
- /etc/profile
- /etc/paths
- ~/.bash_profile
- ~/.bash_login
- ~/.profile
- ~/.bashrc
当然/etc/profile和/etc/paths是系统级别的，系统启动就会加载，后面几个是当前用户级的环境变量。后面3个按照从前往后的顺序读取，如果~/.bash_profile文件存在，则后面的几个文件就会被忽略不读了，如果~/.bash_profile文件不存在，才会以此类推读取后面的文件。~/.bashrc没有上述规则，它是bash shell打开的时候载入的。
设置PATH的语法都为：
export PATH=$PATH:<PATH 1>:<PATH 2>:<PATH 3>:------:<PATH N>
两个方式设置环境变量
修改当前用户的环境变量
推荐方式是修改~/.bash_profile
export ANDROID_HOME=/Users/chenli4/Library/Android/sdk
export PATH=${PATH}:${ANDROID_HOME}/tools
export PATH=${PATH}:${ANDROID_HOME}/platform-tools
export PATH=${PATH}:/Users/chenli4/Library/Android/sdk/platform-tools
# Setting PATH for Python 3.7
# The original version is saved in .bash_profile.pysave
PATH="/Library/Frameworks/Python.framework/Versions/3.7/bin:${PATH}"
export PATH
修改系统的环境变量
推荐方式是修改/etc/profile
# System-wide .profile for sh(1)
if [ -x /usr/libexec/path_helper ]; then
eval `/usr/libexec/path_helper -s`
fi
if [ "${BASH-no}" != "no" ]; then
[ -r /etc/bashrc ] && . /etc/bashrc
fi
JAVA_HOME="/Library/Java/JavaVirtualMachines/jdk-10.0.2.jdk/Contents/Home"
export JAVA_HOME
CLASS_PATH="$JAVA_HOME/lib"
export ANDROID_HOME=/Users/chenli4/Library/Android/sdk
export PATH=${PATH}:${ANDROID_HOME}/tools
export PATH=${PATH}:${ANDROID_HOME}/platform-tools
export PATH=$JAVA_HOME/bin:$PATH
比如把jdk10变成jdk8
打开Sublime Text，修改/etc/profile
JAVA_HOME="/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home"
保存(需要输入密码)
