Re: PSA: Mac OS X El Capitan upgrade might break your $PATH

[Andrew Janke <andrew@apjanke.net>]

On 7/31/15 2:53 PM, Mikael Magnusson wrote:
> On Fri, Jul 31, 2015 at 6:35 PM, Kurtis Rader <krader@skepticism.us> wrote:
>> A public service announcement for those running Zsh on Mac OS X.
>>
>> Upgrading to El Capitan (OS X 10.11) will install a /etc/zprofile that
>> contains
>>
>>      # system-wide environment settings for zsh(1)
>>      if [ -x /usr/libexec/path_helper ]; then
>>         eval `/usr/libexec/path_helper -s`
>>      fi
>>
>> On a new login shell that will be sourced after your $HOME/.zshenv. If you
>> set your $PATH in your .zshenv the /usr/libexec/path_helper program will
>> alter the order of the directories. The order appears random so it's
>> probably using a hashed set to avoid having the same directory appear more
>> than once in the result.
>>
>> You can't remove /usr/libexec/path_helper due to the new security
>> mechanisms (at least not without booting from a recovery disk) but you can
>> remove /etc/zprofile which is what I did to keep my $PATH from being mucked
>> with.
> That's good news, they used to have that code in /etc/zshenv which
> meant you had _no_ way to override it. It only took them a few years
> to fix this.
>
> As a sidenote, it's not a great idea to set your path in .zshenv, you
> should probably move those settings to your .zprofile. (Otherwise,
> running a script that uses zsh will not use the $PATH from the
> environment, which can break things in some situations).
>

I suspect the order of entries in path_helper is determined by 
alphabetical ordering of the filenames in /etc/paths.d, where 
path_helper locates the files that come after the default system paths. 
That "40-" in XQuartz looks like an rcdir-style technique to enforce 
ordering, and I think the XQuartz folks know what they're doing with the 
OS X system stuff. (This is on 10.9.)

$ ls -l /etc/paths.d
total 16
-rw-r--r--   1 root  wheel    13 Aug 11  2014 40-XQuartz
-rw-r--r--   1 root  wheel    12 May  7 21:06 TeX

Playing around with this seems to support that theory. Files read in 
order, duplicate entries removed after the first occurrence.

#/bin/sh
# install-hello-paths - script to test path_helper behavior
echo /hello/world > /etc/paths.d/01-hello
echo /hello/world > /etc/paths.d/99-hello


One other El Capitan change: the system-supplied zsh (5.0.8) appears to 
be compiled with /usr/local/share/zsh/site-functions in the default 
$fpath, which was not the case for earlier versions of OS X. This is 
probably related to the "rootless" stuff that locks down /usr outside 
/usr/local/.

Cheers,
Andrew