[Exherbo-dev] Preserving PATH during shell startup

Bernd Steinhauser exherbo at bernd-steinhauser.de
Sun Oct 28 13:23:56 UTC 2012


On 28/10/12 14:18, Bernd Steinhauser wrote:
> Currently, the way we handle the system environment variables is the use of 
> /etc/env.d, which gets merged by `eclectic env update` to /etc/profile.env.
> In both /etc/profile (used by bash) and /etc/zsh/zprofile (used by zsh), 
> /etc/profile.env is sourced unconditionally, which contains `export 
> PATH='some:paths:'.
> This means that once /etc/profile.env has been sourced, PATH has been reset to 
> whatever is in profile.env + whatever bash or zsh add to it in their startup 
> files.
> This has two consequences:
> 1. You can not pass a custom PATH to a subshell, if the subshell runs one of 
> the startup files that is sourcing /etc/profile.env (I'm 100% sure about the 
> situation for bash, I think it only does so if run as a login or interactive 
> shell)
> 2. Only the case for zsh: A user-customized PATH (in ~/.zshenv) might get 
> overridden if run as an interactive or a login shell (because we set PATH in 
> /etc/zsh/{zprofile,zshrc}. See the ordering of the startup files in [1]. 
> Currently, we tell users to use .zshrc for that instead.
>
> For zsh, we tried to ship around 1. by setting PATH in zprofile and zshrc, 
> which are almost identical, introducing 2.
> Since I'm not really happy about this situation, and since it should be ok to 
> allow setting or modifying PATH in /etc/zsh/zshenv and ~/.zshenv, I wan't to 
> discuss this topic, finding the best solution for exherbo.
>
> One of the solutions (at least for zsh) might be to preserve the current PATH, 
> then source /etc/profile.env, and after that restoring or adding the 
> previously set PATH. We could also make a change that profile.env is only 
> sourced if a condition is met, i.e. [[ -o norcs ]] for zsh. (Actually, it 
> might be desirable to do that even if we tend to use a different solution.)
>
> The other solution might be to stop exporting PATH as is in /etc/profile.env. 
> This could be for example be done by either renaming the var eclectic merges 
> to or renaming the vars in the files in /etc/env.d, i.e. to USERPATH (similar 
> to ROOTPATH). The startup scripts could then use USERPATH (and probably 
> ROOTPATH) to compose PATH.
>
> For zsh I would therefore propose to use something like this for zshenv:
>
> if [[ ! -o norcs ]]; then
>     if [[ -e /etc/profile.env ]]; then
>         . /etc/profile.env
>     fi
> PATH="${PATH}:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:${USERPATH}:${ROOTPATH}"
>     export PATH
>     unset USERPATH ROOTPATH
> fi
>
> That would mean that a modified PATH is preserved, that . /etc/profile.env is 
> only sourced when not running as zsh -f and it will be updated upon every 
> shell startup, for both interactive and non-interactive shells, unless 
> explicitly specified (-f).
>
> I mainly talked about zsh here, because that's where we actually see the 
> problem. I'm not sure about the situation with bash, so I would other people 
> to speak up. Maybe bash shows a different behavior, where no problems occur?
> Since at least the second solution affects all shells, it might be a good idea 
> to discuss it first. Of course, we can just implement the other solution, but 
> before we do so for all shells...
Forgot [1], which is:
[1] http://linux.die.net/man/1/zsh



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