1.在bash下运行：

echo $PATH    > PATH=/home/xxx/bin:/home/xxx/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin

2.$PATH在文件/etc/environment中被定义

cat /etc/environment    > PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games"

3.在$HOME/.profile中有修改

> # set PATH so it includes user's private bin directories    > PATH="$HOME/bin:$HOME/.local/bin:$PATH"

4.在/etc/profile.d/apps-bin-path.sh中有修改

> # Expand $PATH to include the directory where snappy applications go.    > if [ "${PATH#*/snap/bin}" = "${PATH}" ]; then    >     export PATH=$PATH:/snap/bin    > fi

准确的说，不同用户最终看到的$PATH是不同的

另：在/etc/login.defs有以下文字

> #    > # *REQUIRED*  The default PATH settings, for superuser and normal users.    > #    > # (they are minimal, add the rest in the shell startup files)    > ENV_SUPATH	PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin    > ENV_PATH	PATH=/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games

附送代码，运行有惊喜

#include 
     
       int main( int argc, char* argv[], char** envp) {       while(*envp)`         printf("%s\n", *(envp++));`     return 0;   }