C++ の json11 を使う (Read)

次のプログラムで作成した JSON を読みます。
C++ の json11 を使う (Create)

json_read.cpp

// -----------------------------------------------------------------------
/*
	json_read.cpp

					May/28/2018
*/
// -----------------------------------------------------------------------
#include	<iostream>
#include	<fstream>
#include	<string>
#include	<cstring>
#include	<map>

#include "json11.hpp"
// -----------------------------------------------------------------------
using namespace std;
using namespace json11;

typedef	map<string,string> Unit;

// -----------------------------------------------------------------------
string file_to_str_proc (char file_in[])
{
	string chunk = "";

	ifstream ifs (file_in);
	string buf;

	while (ifs && getline (ifs,buf))
		{
		chunk += buf;
		}

	return	chunk;
}

// -----------------------------------------------------------------------
void dict_display_proc (map <string,Unit> dict_aa)
{
	map <string,Unit>:: iterator it = dict_aa.begin ();

	while (it != dict_aa.end ())
		{
		Unit unit_aa = (*it).second;

		cout << (*it).first << "\t";
		cout << unit_aa["name"] << "\t";
		cout << unit_aa["population"] << "\t";
		cout << unit_aa["date_mod"] << endl;

		it++;
		}
}

// -----------------------------------------------------------------------
map <string,Unit> json_to_dict_proc (string str_json)
{
	map <string,Unit> dict_aa;

	string err;
	auto json = Json::parse(str_json, err);

	if (!err.empty())
		{
		printf("Failed: %s\n", err.c_str());
		}
	else
		{
//		printf("Result: %s\n", json.dump().c_str());

		for (auto &kk : json.object_items())
			{
			string key = kk.first.c_str();
			Unit unit_aa;
			for (auto &ll : kk.second.object_items())
				{
				{
				string key_item = ll.first.c_str();
				string vvx = ll.second.string_value();
				if (vvx.length() == 0)
					{
					vvx = ll.second.dump().c_str();
					}
				unit_aa[key_item] = vvx;		
				}
			dict_aa[key] = unit_aa;
			}
		}

	return	dict_aa;
}

// -----------------------------------------------------------------------
int main (int argc, char* argv[])
{
	cerr << "*** 開始 ***\n";

	char file_in[160];

	strcpy (file_in,argv[1]);

	string str_json = file_to_str_proc (file_in);

	map <string,Unit> dict_aa = json_to_dict_proc (str_json);

	dict_display_proc (dict_aa);

	cerr << "*** 終了 ***\n";

	return 0;
}

// -----------------------------------------------------------------------

Makefile

CPLUS_COMMON=/var/www/data_base/common/cplus_common
json_read: json_read.cpp
	clang++ -o json_read json_read.cpp -ljson11
clean:
	rm -f json_read

実行コマンド
./json_read cities.json