Re: [boost] Environment Variables Library?

On Tue, May 19, 2015 at 8:38 AM, Andrey Semashev wrote:

On Tue, May 19, 2015 at 2:27 AM, Gavin Lambert wrote:

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On 19/05/2015 09:23, Michael Ainsworth wrote:

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Such a library would be reasonable small, but do you think it would be a useful addition to Boost? I'm still shaking my head that environment variables aren't better supported by standard C++.

They're more popular in POSIX; but at least on Windows, environment variables are considered old-fashioned and discouraged from use without significant compelling reason.

Is there a reference for such a discouragement? Sure, most Windows-only programs just use registry but I wouldn't say environment variables are discouraged from being used. For instance, most development software, including MSVC, use environment for configuration, and registry is not seen as a replacement.

I'm not sure for other devs but my personal guideline so far is: 1. Don't use the register except if you must (mostly because of requirements from the kind of application you are making). 2. Don't use environment variables except if you must (mostly for dev tools helping locating each other). 3. Prefer user-specific or shared directories to put config data in (config files or databases). The reasons for the first two are mainly to avoid issues like "pollution" of the system with montains of unuseful data (in particular with computers used by non-developers). Part of the source of the issue is the lack of common good uninstallation system, part of it is just historical scars itching (from windows98/me era). There is also the cross-platform code issue: if you want to provide data to the whole system in a cross-platform way, the environment variables is the only way to do so, because there is no register on non-windows platforms (that I know of). The environment variables in windows have a limited size which is small enough to be hit very quickly if you abuse it. For example the famous PATH can be filled with paths to tools like git,hg,svn, python, ruby, your favorite C++ compilers and hit the point where you can't add anything anymore. Of course, this can be worked aroudn but it's still an annoying limitation. Finally there is the "it's a public global state" issue, which I kind of like public global non-const variables in a program. It's just problematic. I'm not a specialist of the windows specifics so any of my assumptions might be wrong.

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