Setting environment variables on OS X

Question

What is the proper way to modify environment variables like PATH in OS X?

I\'ve looked on Google a little bit and found three different files to edit:

Answer 1

While the answers here aren't "wrong", I'll add another: never make environment variable changes in OS X that affect "all processes", or even, outside the shell, for all processes run interactively by a given user.

In my experience, global changes to environment variables like PATH for all processes are even more likely to break things on OS X than on Windows. Reason being, lots of OS X applications and other software (including, perhaps especially, components of the OS itself) rely on UNIX command-line tools under the hood, and assume the behavior of the versions of these tools provided with the system, and don't necessarily use absolute paths when doing so (similar comments apply to dynamically-loaded libraries and DYLD_* environment variables). Consider, for instance, that the highest-rated answers to various Stack Overflow questions about replacing OS X-supplied versions of interpreters like Python and Ruby generally say "don't do this."

OS X is really no different than other UNIX-like operating systems (e.g., Linux, FreeBSD, and Solaris) in this respect; the most likely reason Apple doesn't provide an easy way to do this is because it breaks things. To the extent Windows isn't as prone to these problems, it's due to two things: (1) Windows software doesn't tend to rely on command-line tools to the extent that UNIX software does, and (2) Microsoft has had such an extensive history of both "DLL hell" and security problems caused by changes that affect all processes that they've changed the behavior of dynamic loading in newer Windows versions to limit the impact of "global" configuration options like PATH.

"Lame" or not, you'll have a far more stable system if you restrict such changes to smaller scopes.