摘要：export和alias都是用来简化命令行输入的工具。export用于设置环境变量，环境变量是一些系统级别的变量，用于指定一些系统的默认值或者搜索路径等。
alias用于给较长的命令取别名，只是给命令取别名。
一、alias
alias ll="ls -l"这样就可以使用简单的命令执行操作
二、export
环境变量配置文件.bash_profile：
# Setting PATH for Python 3.6 # The original version is saved in .bash_profile.pysave PATH="/Library/Frameworks/Python.framework/Versions/3.6/bin:${PATH}" export PATH # Setting PATH for Python 3.10 # The original version is saved in .bash_profile.pysave
# 冒号(:)通常表示分隔符，将前面的路径添加到PATH系统环境变量中,再调用export设置，最后保存文件别忘了source激活
PATH="/Library/Frameworks/Python.framework/Versions/3.10/bin:${PATH}" export PATH alias python3="/usr/local/bin/python3.10" alias python36="/usr/local/bin/python3.6"注意点:
当我输入$PATH查看系统的环境变量时
-bash: /Library/Frameworks/Python.framework/Versions/3.10/bin:/Library/Frameworks/Python.framework/Versions/3.6/bin:/Library/Frameworks/Python.framework/Versions/3.10/bin:/Library/Frameworks/Python.framework/Versions/3.10/bin:/Library/Frameworks/Python.framework/Versions/3.6/bin:/Library/Frameworks/Python.framework/Versions/3.10/bin:/Library/Frameworks/Python.framework/Versions/3.6/bin:/Library/Frameworks/Python.framework/Versions/3.10/bin:/Library/Frameworks/Python.framework/Versions/3.6/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin: No such file or directory所以当我没加别名alias时，输入python3加载的是python3.10版本而不是3.6版本。（linux中当我输入命令,会到系统环境变量指定的目录中查找可执行文件，没有找到则报错），这里优先找到了3.10/bin下的python3