semioticpixels scratch pad

Managing Paths

The problem with setting up an environment piecemeal is when you sit down to do something, you have to figure out what rabbit hole you’d gone down when you left off. In this case, I remembered installing mysql, but usually the last thing I do when I install mysql is install phpmyadmin because it’s such a handy productivity tool. Well, there was no phpmyadmin on my system, but that could be because Snow Leopard came with PHP 5.3 out of the box which is incompatible with most of the popular PHP web applications out there.

Anyhoo … so I started by checking my $PATH variable and was surprised by the output.

echo $PATH gave me duplicates of /usr/local and /opt/local et. al. and had stuff in it that wasn’t in my ~/.profile

my ~/.profile had the following in it:

export PATH=/usr/local/sbin:/usr/local/mysql/bin:$PATH
##
# Your previous /Users/username/.profile file was backed up as /Users/username/.profile.macports-saved_2009-12-29_at_11:21:58
##
# MacPorts Installer addition on 2009-12-29_at_11:21:58: adding an appropriate PATH variable for use with MacPorts.
export PATH=/opt/local/bin:/opt/local/sbin:$PATH
# Finished adapting your PATH environment variable for use with MacPorts.


and the second entry made by MacPorts was overriding the first entry.

Pretty funky.

TheTao of Path Variables

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/path and /etc/manpath which contain the initial path environment variables. /etc/path 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.

References

man page for path_helper
making use of paths.d
mastering the path_helper