c++读取.ini配置文件

首先添加如下的Config.cpp和Config.h文件到相应目录。
代码来源： https://github.com/wangying2016/Config

//Config.h  
#pragma once  

#include <string>  
#include <map>  
#include <iostream>  
#include <fstream>  
#include <sstream>  


/*
* \brief Generic configuration Class
*
*/
class Config {
	// Data  
protected:
	std::string m_Delimiter;  //!< separator between key and value  
	std::string m_Comment;    //!< separator between value and comments  
	std::map<std::string, std::string> m_Contents;  //!< extracted keys and values  

	typedef std::map<std::string, std::string>::iterator mapi;
	typedef std::map<std::string, std::string>::const_iterator mapci;
	// Methods  
public:

	Config(std::string filename, std::string delimiter = "=", std::string comment = "#");
	Config();
	template<class T> T Read(const std::string& in_key) const;  //!<Search for key and read value or optional default value, call as read<T>  
	template<class T> T Read(const std::string& in_key, const T& in_value) const;
	template<class T> bool ReadInto(T& out_var, const std::string& in_key) const;
	template<class T>
	bool ReadInto(T& out_var, const std::string& in_key, const T& in_value) const;
	bool FileExist(std::string filename);
	void ReadFile(std::string filename, std::string delimiter = "=", std::string comment = "#");

	// Check whether key exists in configuration  
	bool KeyExists(const std::string& in_key) const;

	// Modify keys and values  
	template<class T> void Add(const std::string& in_key, const T& in_value);
	void Remove(const std::string& in_key);

	// Check or change configuration syntax  
	std::string GetDelimiter() const { return m_Delimiter; }
	std::string GetComment() const { return m_Comment; }
	std::string SetDelimiter(const std::string& in_s)
	{
		std::string old = m_Delimiter;  m_Delimiter = in_s;  return old;
	}
	std::string SetComment(const std::string& in_s)
	{
		std::string old = m_Comment;  m_Comment = in_s;  return old;
	}

	// Write or read configuration  
	friend std::ostream& operator<<(std::ostream& os, const Config& cf);
	friend std::istream& operator>>(std::istream& is, Config& cf);

protected:
	template<class T> static std::string T_as_string(const T& t);
	template<class T> static T string_as_T(const std::string& s);
	static void Trim(std::string& inout_s);


	// Exception types  
public:
	struct File_not_found {
		std::string filename;
		File_not_found(const std::string& filename_ = std::string())
			: filename(filename_) {}
	};
	struct Key_not_found {  // thrown only by T read(key) variant of read()  
		std::string key;
		Key_not_found(const std::string& key_ = std::string())
			: key(key_) {}
	};
};


/* static */
template<class T>
std::string Config::T_as_string(const T& t)
{
	// Convert from a T to a string  
	// Type T must support << operator  
	std::ostringstream ost;
	ost << t;
	return ost.str();
}


/* static */
template<class T>
T Config::string_as_T(const std::string& s)
{
	// Convert from a string to a T  
	// Type T must support >> operator  
	T t;
	std::istringstream ist(s);
	ist >> t;
	return t;
}


/* static */
template<>
inline std::string Config::string_as_T<std::string>(const std::string& s)
{
	// Convert from a string to a string  
	// In other words, do nothing  
	return s;
}


/* static */
template<>
inline bool Config::string_as_T<bool>(const std::string& s)
{
	// Convert from a string to a bool  
	// Interpret "false", "F", "no", "n", "0" as false  
	// Interpret "true", "T", "yes", "y", "1", "-1", or anything else as true  
	bool b = true;
	std::string sup = s;
	for (std::string::iterator p = sup.begin(); p != sup.end(); ++p)
		*p = toupper(*p);  // make string all caps  
	if (sup == std::string("FALSE") || sup == std::string("F") ||
		sup == std::string("NO") || sup == std::string("N") ||
		sup == std::string("0") || sup == std::string("NONE"))
		b = false;
	return b;
}


template<class T>
T Config::Read(const std::string& key) const
{
	// Read the value corresponding to key  
	mapci p = m_Contents.find(key);
	if (p == m_Contents.end()) throw Key_not_found(key);
	return string_as_T<T>(p->second);
}


template<class T>
T Config::Read(const std::string& key, const T& value) const
{
	// Return the value corresponding to key or given default value  
	// if key is not found  
	mapci p = m_Contents.find(key);
	if (p == m_Contents.end()) return value;
	return string_as_T<T>(p->second);
}


template<class T>
bool Config::ReadInto(T& var, const std::string& key) const
{
	// Get the value corresponding to key and store in var  
	// Return true if key is found  
	// Otherwise leave var untouched  
	mapci p = m_Contents.find(key);
	bool found = (p != m_Contents.end());
	if (found) var = string_as_T<T>(p->second);
	return found;
}


template<class T>
bool Config::ReadInto(T& var, const std::string& key, const T& value) const
{
	// Get the value corresponding to key and store in var  
	// Return true if key is found  
	// Otherwise set var to given default  
	mapci p = m_Contents.find(key);
	bool found = (p != m_Contents.end());
	if (found)
		var = string_as_T<T>(p->second);
	else
		var = value;
	return found;
}


template<class T>
void Config::Add(const std::string& in_key, const T& value)
{
	// Add a key with given value  
	std::string v = T_as_string(value);
	std::string key = in_key;
	Trim(key);
	Trim(v);
	m_Contents[key] = v;
	return;
}

// Config.cpp  

#include "Config.h"  

using namespace std;


Config::Config(string filename, string delimiter,
	string comment)
	: m_Delimiter(delimiter), m_Comment(comment)
{
	// Construct a Config, getting keys and values from given file  

	std::ifstream in(filename.c_str());

	if (!in) throw File_not_found(filename);

	in >> (*this);
}


Config::Config()
	: m_Delimiter(string(1, '=')), m_Comment(string(1, '#'))
{
	// Construct a Config without a file; empty  
}



bool Config::KeyExists(const string& key) const
{
	// Indicate whether key is found  
	mapci p = m_Contents.find(key);
	return (p != m_Contents.end());
}


/* static */
void Config::Trim(string& inout_s)
{
	// Remove leading and trailing whitespace  
	static const char whitespace[] = " \n\t\v\r\f";
	inout_s.erase(0, inout_s.find_first_not_of(whitespace));
	inout_s.erase(inout_s.find_last_not_of(whitespace) + 1U);
}


std::ostream& operator<<(std::ostream& os, const Config& cf)
{
	// Save a Config to os  
	for (Config::mapci p = cf.m_Contents.begin();
		p != cf.m_Contents.end();
		++p)
	{
		os << p->first << " " << cf.m_Delimiter << " ";
		os << p->second << std::endl;
	}
	return os;
}

void Config::Remove(const string& key)
{
	// Remove key and its value  
	m_Contents.erase(m_Contents.find(key));
	return;
}

std::istream& operator>>(std::istream& is, Config& cf)
{
	// Load a Config from is  
	// Read in keys and values, keeping internal whitespace  
	typedef string::size_type pos;
	const string& delim = cf.m_Delimiter;  // separator  
	const string& comm = cf.m_Comment;    // comment  
	const pos skip = delim.length();        // length of separator  

	string nextline = "";  // might need to read ahead to see where value ends  

	while (is || nextline.length() > 0)
	{
		// Read an entire line at a time  
		string line;
		if (nextline.length() > 0)
		{
			line = nextline;  // we read ahead; use it now  
			nextline = "";
		} else
		{
			std::getline(is, line);
		}

		// Ignore comments  
		line = line.substr(0, line.find(comm));

		// Parse the line if it contains a delimiter  
		pos delimPos = line.find(delim);
		if (delimPos < string::npos)
		{
			// Extract the key  
			string key = line.substr(0, delimPos);
			line.replace(0, delimPos + skip, "");

			// See if value continues on the next line  
			// Stop at blank line, next line with a key, end of stream,  
			// or end of file sentry  
			bool terminate = false;
			while (!terminate && is)
			{
				std::getline(is, nextline);
				terminate = true;

				string nlcopy = nextline;
				Config::Trim(nlcopy);
				if (nlcopy == "") continue;

				nextline = nextline.substr(0, nextline.find(comm));
				if (nextline.find(delim) != string::npos)
					continue;

				nlcopy = nextline;
				Config::Trim(nlcopy);
				if (nlcopy != "") line += "\n";
				line += nextline;
				terminate = false;
			}

			// Store key and value  
			Config::Trim(key);
			Config::Trim(line);
			cf.m_Contents[key] = line;  // overwrites if key is repeated  
		}
	}

	return is;
}
bool Config::FileExist(std::string filename)
{
	bool exist = false;
	std::ifstream in(filename.c_str());
	if (in)
		exist = true;
	return exist;
}

void Config::ReadFile(string filename, string delimiter,
	string comment)
{
	m_Delimiter = delimiter;
	m_Comment = comment;
	std::ifstream in(filename.c_str());

	if (!in) throw File_not_found(filename);

	in >> (*this);
}

测试文件：

#include <iostream>
#include <cstdlib>
#include <string>
#include <fstream>
#include <libgen.h>
#include <unistd.h>
#include "utils/readConfig.h"

int main(int argc,char* argv[])
{
    chdir(dirname(argv[0]));
	std::string config_filename("../config/config.ini");
	Config config(config_filename);
	std::string param_key = "pointcloud_topic";
	std::string pointcloud_topic;
	pointcloud_topic = config.Read<std::string>(param_key);
	std::cout << "Read Key " << param_key << "'s Value is " 
		 << pointcloud_topic << std::endl;
	return 0;
}

config.ini中的内容：

# config param , key = value
pointcloud_topic = /camera/depth/color/points