Programmatically Get at Memory Usage via Proc Status

memory_status.cpp

#include <fstream>
#include <string>
#include <iostream>
#include <cinttypes>
#include <utility>
#include <algorithm>
#include <unordered_map>
#include <unordered_set>
#include <list>

struct memory_status {
  memory_status(const std::unordered_set<std::string> interest = {}){
    //grab the vm stats from the file
    std::ifstream file("/proc/self/status");
    std::string line;
    while(std::getline(file, line)){
      //did we find a memory metric
      if(line.find_first_of("Vm") == 0){
        //grab the name of it and see if we care about it
        std::string name = line.substr(0, line.find_first_of(':'));
        if(interest.size() > 0 && interest.find(name) == interest.end())
          continue;
        //try to get the number of bytes
        std::remove_if(line.begin(), line.end(), [](const char c) {return !std::isdigit(c);});
        if(line.size() == 0)
          continue;
        auto bytes = std::stod(line) * 1024.0;
        //get the units and scale
        std::pair<double, std::string> metric = std::make_pair(bytes, "b");
        for(auto unit : { "B", "KB", "MB", "GB" }){
          metric.second = unit;
          if (metric.first > 1024.0)
            metric.first /= 1024.0;
          else
            break;
        }
        metrics.emplace(std::piecewise_construct, std::forward_as_tuple(name), std::forward_as_tuple(metric));
      }
      line.clear();
    }
  }

  std::unordered_map<std::string, std::pair<double, std::string> > metrics;

  friend std::ostream& operator<<(std::ostream&, const memory_status&);
};

std::ostream& operator<<(std::ostream& stream, const memory_status& s){
  for(const auto& metric : s.metrics)
    stream << metric.first << ": " << metric.second.first << metric.second.second << std::endl;
  return stream;
}

int main(){

  std::list<uint32_t> ints;
  for(uint32_t i = 0; i < std::numeric_limits<uint32_t>::max() / 100; ++i)
    ints.push_back(i);

  std::cout << memory_status({"VmSize", "VmPeak", "VmRss", "VmSwap"});

  return 0;
}