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Unix FAQ and PATH (for OSX)

Must read!

http://hayne.net/MacDev/Notes/unixFAQ.html

It includes a very nice explanation about when and how /etc/profile, ~/profile, ~/.bash_profile, ~/.bash_login and friends are loaded up!

And a more detailed explanation on how PATH is constructed in OSX can be found here. In summary, it goes like this:

  1. /etc/profile is the default startup script for Bash, which is what I’m using. (If you’re using a different shell, then you may have a different startup script). /etc/profile calls /usr/libexec/path_helper
  2. path_helper first calls /etc/paths and /etc/manpaths which contain the initial path environment variables. /etc/paths contains system-wide defaults:
    /usr/bin /bin /usr/sbin /sbin /usr/local/bin
  3. path_helper then looks for files in the directories: /etc/paths.d and /etc/manpaths.d and appends the paths found there. On my system, /etc/paths.d and /etc/manpaths.d contain a file named X11 which simply contains the paths for X11.
  4. After /etc/profile has called path_helper, it then looks for /etc/.bashrc. I have a bashrc (no “.”), but my bashrc only has stuff in it specifying the bash shell prompt (name-of-my-computer:directory username$)
  5. Bash next looks for ~/.bash_profile. This is the file where you’ll set file and directory colors and could also be where you place your Path environment variables. Obviously, ~/ represents your user directory, so your settings will only be valid for your user.
  6. Next, bash looks for ~/.bash_login. I don’t have this on my system so it’s ignored in my case
  7. next, bash looks for ~/.profile which I did have on my system and is the file that XCode wrote to.

Another file that can contain path variables is ~/.MacOSX/environment.plist. This sets environment variables, including paths, for gui applications. I’m not using it on my system so don’t have anything to say about it.

Recap

So, what that all means is that instead of exporting PATH environment variables to a .profile or .bash_profile in a user account directory, you (or your application) can, instead, make PATHs global by adding text files to the /etc/paths.d and /etc/manpaths.d directories.

If you need to control the order of a path, then try this:
Add a line PATH=”” before the call to path_helper like this in /etc/profile:

if [ -x /usr/libexec/path_helper ]; then PATH="" eval `/usr/libexec/path_helper -s` fi

All that said and done … I’ll continue using ~/.bash_profile because it’s got that warm fuzzy familiarity. Personal preference, as always.

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