Linux shell 如何避免重复加载环境变量？

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问题内容

使用

zsh

source

shell

原本的环境变量：?

─➤  echo -e ${PATH//:/\\n}
/home/bot/.cargo/bin
/home/bot/opt/go/bin
/home/bot/.local/bin
/home/bot/opt/pycharm/pycharm-2021.2/bin
/home/bot/opt/python3.10.1/bin
/usr/local/sbin
/usr/local/bin
/usr/sbin
/usr/bin
/sbin
/bin
/usr/games
/usr/local/games
/snap/bin

子

shell

─➤  echo -e ${PATH//:/\\n}
/home/bot/.local/share/virtualenvs/ideaboom-3stdf9Mx/bin
/home/bot/opt/go/bin
/home/bot/.local/bin
/home/bot/opt/pycharm/pycharm-2021.2/bin
/home/bot/opt/python3.10.1/bin
/home/bot/.cargo/bin
/home/bot/opt/go/bin
/home/bot/.local/bin
/home/bot/opt/pycharm/pycharm-2021.2/bin
/home/bot/opt/python3.10.1/bin
/usr/local/sbin
/usr/local/bin
/usr/sbin
/usr/bin
/sbin
/bin
/usr/games
/usr/local/games
/snap/bin

可以看到开头这部分变量被重新加载了?

/home/bot/opt/go/bin
/home/bot/.local/bin
/home/bot/opt/pycharm/pycharm-2021.2/bin
/home/bot/opt/python3.10.1/bin

造成重复加载环境变量的原因，我猜测是每个子

shell

~/.zshenv

我的

~/.zshenv

export RUSTUP_DIST_SERVER=https://mirrors.ustc.edu.cn/rust-static/
export RUSTUP_UPDATE_ROOT=https://mirrors.ustc.edu.cn/rust-static//rustup
export PATH=/home/bot/opt/python3.10.1/bin:$PATH
export PATH=/home/bot/opt/pycharm/pycharm-2021.2/bin:$PATH
export PATH=/home/bot/.local/bin:$PATH
export PATH=/home/bot/opt/go/bin:$PATH

. "$HOME/.cargo/env"

其中的

"$HOME/.cargo/env"

"$HOME/.cargo/env"

#!/bin/sh
# rustup shell setup
# affix colons on either side of $PATH to simplify matching
case ":${PATH}:" in
    *:"$HOME/.cargo/bin":*)
        ;;
    *)
        # Prepending path in case a system-installed rustc needs to be overridden
        export PATH="$HOME/.cargo/bin:$PATH"
        ;;
esac

但是这个脚本的

shell

shell

越简单优雅越好！???

正确答案

楼上的方法也是不恰当的，因为它要么存在一个就全部不再加，要么一次性全部加上，其实正确的脚本应该是

#!/bin/sh
# rustup shell setup
# 下面分别对每个路径进行测试，判断是否需要增加到PATH环境变量中去。
case ":${PATH}:" in
    *:"${HOME}/opt/go/bin":*)
        ;;
    *)
        export PATH=${HOME}/opt/go/bin:${PATH}
        ;;
esac

case ":${PATH}:" in
    *:"${HOME}/.local/bin":*)
        ;;  
    *)
        export PATH=${HOME}/.local/bin:${PATH}  
        ;;
esac
   
case ":${PATH}:" in
    *:"${HOME}/opt/pycharm/pycharm-2021.2/bin":*)
        ;;    
    *)
        export PATH=${HOME}/opt/pycharm/pycharm-2021.2/bin:${PATH} 
        ;;
esac    

case ":${PATH}:" in
    *:"${HOME}/opt/python3.10.1/bin":*)
        ;;
    *)
        export PATH=${HOME}/opt/python3.10.1/bin:${PATH} 
        ;;
esac

另外一种写法可能更简洁，总之一个原则是判断PATH中是否包含待加入的路径:

#!/bin/sh
# 下面分别对每个路径进行测试，判断是否需要增加到PATH环境变量中去。
if [[ ":${PATH}:" != *":${HOME}/opt/go/bin:"* ]]; then
    export PATH=${HOME}/opt/go/bin:${PATH}
fi

if [[ ":${PATH}:" != *":${HOME}/.local/bin:"* ]]; then
    export PATH=${HOME}/.local/bin:${PATH}
fi

if [[ ":${PATH}:" != *":${HOME}/opt/pycharm/pycharm-2021.2/bin:"* ]]; then
    export PATH=${HOME}/opt/pycharm/pycharm-2021.2/bin:${PATH}
fi

if [[ ":${PATH}:" != *":${HOME}/opt/python3.10.1/bin:"* ]]; then
    export PATH=${HOME}/opt/python3.10.1/bin:${PATH}
fi

这里的关键是用

*

:

PATH

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