Variable substitution in the environment.plist file

Question

I want an additional item in the PATH environment variable for GUI-launched apps. I've created the ~/.MacOSX/environment.plist file and added an entry to create a PATH variable. I have initially tried to set the value of this to
"$(PATH):/usr/local"
in an attempt to append the /usr/local folder to the path. However, the PATH value appears to be exactly what I've set it to - without the substitution.
1) Is there a way to get the existing value substituted in?
2) As I'm always out to learn new things, is there a better way of achieving this?
(My fundamental problem is that I have written a plugin for XCode and I'm trying to not hard code the location of a compiler into it. Therefore I thought I'd use the PATH variable to let me find it. However the default PATH value doesn't include /usr/local which is where the compiler is located. So I'm looking for a way to add this folder into the PATH value, and the ~/.MacOSX/environment.plist seemed to be what I wanted - as long as I can get the substitution going. Otherwise I have to hard code the path into THAT file which I feel is just as bad!).
Thanks
Susan

Answer 1

Hi Susan,
   I'm sorry; I didn't mean to imply that this is the wrong place to ask the question. I hope that it's the best place. I was just trying to explain, mostly to myself, why everyone assumes that the part of the system that reads the environment.plist will behave like a shell.
   If you were worried about hard-coding the path on your own machine, I would say that you needn't worry. The only path that exists prior to the setting of environment variables from the environment.plist is hard-coded into the system somewhere. A while back someone found it but that's not really important. If you want to start with that default, you can. If you need to know what it is, I'm sure that we can find it for you somewhere. I assume it's along the lines of:
/usr/bin:/bin:/usr/sbin:/sbin
   While I'm not telling you to not do it, I suggest that you rethink setting the user's path an environment.plist. Changing the environment of every last one of a user's processes "behind the back" of the user seems a bit presumptuous. It wouldn't be a problem if you set a variable that no other app could recognize but if you added something to my path, my first thought would be to look there for a trojan horse. I would eventually realize that it was misguided instead of malicious but I wouldn't like it. It also stands some chance of changing the behavior of a user's UNIX applications.
   If you distribute an environment.plist file with your plugin, you would also have to address the issue of users that already have such files. Thus, it would seem that you would need to do a little checking in an install script. That being the case, you could evaluate the user's PATH variable in that script and use it to hard-code the path in an environment.plist that you generate programmatically from the install script at runtime. Such a script would also give you the opportunity to ask the user if he wants an environment.plist file.
   Of course that approach would make it difficult for a user to remove an element from his path; it wouldn't be sufficient to cease adding the element to the path in the user's shell startup scripts. You would probably be better off using the default path. That might not interfere with changes the user makes in his shell startup scripts but it would mine. You added /usr/local/bin to the end of a user's path. My startup scripts only add path elements if they aren't already there. However, I want /usr/local/bin in front of the default part of my path so your change would alter the behavior of my system.
   If you want to change the environment of a single application, it is common to "wrap" its invocation in a script that sets the environment before invoking the application. However, I'm not sure how that would work with an Xcode plugin.
Gary
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   There are only 10 kinds of people in the world. Those
   who understand binary numbers and those who don't.