Get RSS without forking on MacOS X or Windows

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These might be helpful:

• http://nadeausoftware.com/articles/2012/07/c_c_tip_how_get_process_resident_set_size_physical_memory_use (see getCurrentRSS)
• http://www.opensource.apple.com/source/adv_cmds/adv_cmds-147/ps/
• http://www.opensource.apple.com/tarballs/adv_cmds/adv_cmds-147.tar.gz
• http://cpansearch.perl.org/src/JSWARTZ/Proc-ProcessTable-0.46/os/

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OSX: It appears ps is signed or whitelisted to allow some syscalls, possibly including task_for_pid

Simple test:

Regular ps

$ ps -opid,rss
  PID    RSS
50351   5040
81222   6028
22750   5008
24728    540
24729    540
56332   2600
52229   4864

Copy of ps

$ cp /bin/ps ~/bin_ps && ~/bin_ps -opid,rss && rm ~/bin_ps
  PID    RSS
50351      0
81222      0
22750      0
24728      0
24729      0
56332      0
52229      0
56699    548

[Kazuki Ohta]

pull request are welcomed. the current committers assume that this gem is used at Linux on production environment.

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TL;DR: Reading RSS from another pid is likely not possible on OSX.