env -0 not supported on macOS

[chaselgrove]

reproman/resource/session.py uses env -0 to get the environment, but -0 is not a supported option to env on macOS.

[yarikoptic]

my workaround idea was to dump + parse /proc/PID/environ - but it seems there is no /proc on osx (mach), so would be only linux specific

[yarikoptic]

@kyleam : perl -e "print %ENV"

[kyleam]

@chaselgrove and I discussed this a bit on the call. A couple of points:

• We talked about why, if we're going to dump the environment with a language, perl should be preferred to python. I said I thought the thinking was that it's more likely that minimal resources/containers will have perl. I think @chaselgrove was unconvinced, and, thinking about it more, I'm not sure that really holds water in general. While it's true that debian:*-slim has perl but not python, other minimal images like alpine and busybox have neither (nor do they have an env that supports -0). And I suspect it'd be quite rare for a server to not have some version of python.

• @chaselgrove mentioned that using python/perl to grab the values would mean non-exported variables aren't included. But that's the case with env anyway at least on my system (i.e. with GNU coreutil's env). So I think that's okay.

Anyway, here are my two snippets to imitate env -0:

• python -c "import os; import sys; sys.stdout.write('\0'.join('{}={}'.format(k, v) for k, v in os.environ.items()))"

• perl -e 'foreach (keys %ENV) {print "$_=$ENV{$_}\0";}'

[yarikoptic]

perl is the winner! ;-) @chaselgrove please run perl version if env -0 fails