Hi Gottfried,

I hope this strikes the right balance between explaining 
‘environment variables’ from scratch and answering your immediate 
question.

Gottfried 写道：
> 1.  Will this now overwrite my variables for ever, or only for 
> some time?

Environment variables are not saved.  They can be *set* by 
configuration files, such at /etc/profile, but these files are not 
updated when you type ‘export GUIX=awesome’ on the command line.

Setting LC_ALL like this affects your current shell, and it will 
be inherited by child processes (hence why the ‘guix’ child will 
speak English after setting LC_ALL=C in the parent shell), but 
they exist purely in RAM for the lifetime of each process.

The also do not propagate to ancestor or sibling processes: 
setting LC_ALL in one terminal window has no effect on any other 
windows.  Nor will setting LC_ALL in a shell affect new processes 
you launch elsewhere, such as from your desktop menu.  Only child 
processes launched in the same shell/window will inherit it.

As soon as you close that terminal, type ‘exit’ in the (guix) 
shell, or trip over your power cable, the setting is gone.

> 2.  How can I set it back to my original state?

Environment variables have no built-in notion of history, or 
defaults.  They are just variables, and setting them to something 
new overwrites the old value (if any).

So:

~$ echo $LC_ALL		# yours will be de_DE, I presume
en_IE.utf8
~$ LC_OLD=$LC_ALL	# save the old value
~$ export LC_ALL=C	# in with the new
~$ echo $LC_ALL		# do the thing
C
~$ LC_ALL=$LC_OLD	# restore the old value

But really, in practice, I'd just close the window/shell once 
done…  they are so cheap.

Kind regards,

T G-R