There is no such thing as an exported or non-exported environment variable. In fact, as the kernel is concerned, there is no such thing as an environment _varia

There is no such thing as an exported or non-exported environment variable. In fact, as the kernel is concerned, there is no such thing as an environment _variable_ at all, just a block of data. See execve(2): "envp is an array of pointers to strings, conventionally of the form key=value, which are passed as the environment of the new program. The envp array must be terminated by a NULL pointer." You can confirm this my examining the the environment block that was passed in to your current shell with: < /proc/$$/environ tr '\0' '\n' What you're referring to are actually "shell parameters", some of which may be marked for export. When the shell starts up, it parses the environment block and sets parameters based on what it finds, marking them all for export. And the shell uses only the parameters marked for export when constructing the environment block for a child process (which is passed to execve(2)/execveat(2) in the envp argument).