根据/proc/meminfo对空闲内存进行占用

#include <stdio.h>#include <sys/sysinfo.h>
#include <linux/kernel.h>     /* 包含sysinfo结构体信息*/
#include <unistd.h>#include <string>
#include <iostream>
#include <fstream>
#include <map>
#include <vector>
#include <assert.h>
#include <stdlib.h>
using namespace std;///
// Item Names which should be corresponded to the enum below restrictly
const char * ItemCheckName[] = 
{"MemTotal","MemFree","Buffers","Cached"
};enum ITEMCHECKNAME
{MEMTOTAL = 0,MEMFREE,BUFFERS,CACHED
};const int INVALID_VALUE = -1;
const char* MEM_INFO_FILE_NAME = "/proc/meminfo";
bool isDebugging = false;
//    string trim(const string& str)
{string::size_type pos = str.find_first_not_of(' ');if (pos == string::npos){return str;}string::size_type pos2 = str.find_last_not_of(' ');if (pos2 != string::npos){return str.substr(pos, pos2 - pos + 1);}return str.substr(pos);
}int split(const string& str, vector<string>& ret_, string sep = ",")
{if (str.empty()){return 0;}string tmp;string::size_type pos_begin = str.find_first_not_of(sep);string::size_type comma_pos = 0;while (pos_begin != string::npos){comma_pos = str.find(sep, pos_begin);if (comma_pos != string::npos){tmp = str.substr(pos_begin, comma_pos - pos_begin);pos_begin = comma_pos + sep.length();}else{tmp = str.substr(pos_begin);pos_begin = comma_pos;}if (!tmp.empty()){ret_.push_back(tmp);tmp.clear();}}return 0;
}bool CheckAllBeenSet(vector<pair<string, int> > itemsToCheck)
{vector<pair<string, int> >::iterator it = itemsToCheck.begin();while (it != itemsToCheck.end()){if (it->second == INVALID_VALUE){return false;}it++;}return true;
}void PrintItems(vector<pair<string, int> > itemsToCheck)
{vector<pair<string, int> >::iterator it = itemsToCheck.begin();while (it != itemsToCheck.end()){cout << "KEY = " << it->first << " , VALUE = " << it->second << " KB "<< endl;it++;}
}unsigned int CheckFreeMemInKByte(vector<pair<string, int> > itemsToCheck)
{// 空闲内存计算方式：如果Cached值大于MemTotal值则空闲内存为MemFree值，否则空闲内存为MemFree值+Buffers值+Cached值int rlt;if (itemsToCheck[CACHED].second > itemsToCheck[MEMTOTAL].second){    rlt = itemsToCheck[MEMFREE].second;if (isDebugging){cout << "CACHED(" << itemsToCheck[CACHED].second << "KB) > MEMTOTAL(" << itemsToCheck[MEMTOTAL].second << "KB)\n";cout << "FreeMemInKb is " << rlt << "KB\n";}}else{rlt = itemsToCheck[CACHED].second + itemsToCheck[MEMFREE].second + itemsToCheck[BUFFERS].second;if (isDebugging){cout << "CACHED(" << itemsToCheck[CACHED].second << "KB) <= MEMTOTAL(" << itemsToCheck[MEMTOTAL].second << "KB)\n";cout << "FreeMemInKb is " << rlt << "KB\n";}}return rlt;
}// usage 
int main(int argc, char *agrv[])
{if (argc < 3 || argc > 4){cout << "Usage :\n memCons fromTotalMem freePercentage [isDebugging]\n";cout << "For example : \'memCons 0 1\'\n means to take 99% of freeMem, that is to leave only 1% out of free memory\n";cout << "For example : \'memCons 1 1\'\n means to take 99% of totalMem, that is to leave only 1% out of all the memory\n";cout << "For example : \'memCons 1 1 1\'\n means in the debugging mode\n";return -1;}bool fromTotalMem = atoi(agrv[1]) == 1 ? true : false;int freePercentage = atoi(agrv[2]);isDebugging = (argc == 4 && atoi(agrv[3]) == 1) ? true : false;if (!(freePercentage > 0 && freePercentage < 100)){cout << "the second argument of memCons must between 0 and 100";return -1;}struct sysinfo s_info;int error;error = sysinfo(&s_info);printf("the followings are output from \'sysinfo\' call \n\ncode error=%d\n",error);printf("Uptime = %ds\nLoad: 1 min%d / 5 min %d / 15 min %d\n""RAM: total %d / free %d /shared%d\n""Memory in buffers = %d\nSwap:total%d/free%d\n""Number of processes = %d\n\n\n",s_info.uptime, s_info.loads[0],s_info.loads[1], s_info.loads[2],s_info.totalram, s_info.freeram,s_info.totalswap, s_info.freeswap,s_info.procs );vector< pair<string, int> > itemsToCheck;std::pair <std::string, int> memTotal(ItemCheckName[MEMTOTAL], INVALID_VALUE);itemsToCheck.push_back(memTotal);std::pair <std::string, int> memfreePair(ItemCheckName[MEMFREE], INVALID_VALUE);itemsToCheck.push_back(memfreePair);std::pair <std::string, int> buffers(ItemCheckName[BUFFERS], INVALID_VALUE);itemsToCheck.push_back(buffers);std::pair <std::string, int> cached(ItemCheckName[CACHED], INVALID_VALUE);itemsToCheck.push_back(cached);vector<string> splitedWords;ifstream infile(MEM_INFO_FILE_NAME);          if (infile.fail()){cerr << "error in open the file";return false;}int hitCnt = itemsToCheck.size();    while(hitCnt != 0){splitedWords.clear();char temp[100];infile.getline(temp, 100); const string tmpString = temp;split(tmpString, splitedWords, ":"); // use the first part to check whether to continuesplitedWords[0] = trim(splitedWords[0]);int foundIndex = -1;for (int i = 0; i < itemsToCheck.size(); i++){if (itemsToCheck[i].first == splitedWords[0]){foundIndex = i;hitCnt--;break;}}if (foundIndex  == -1){continue;}// check the numberstring numberInString = trim(splitedWords[1]);int firstNotNumberPos = numberInString.find_first_not_of("123456789");numberInString.substr(0, firstNotNumberPos);int num = atoi(numberInString.c_str());// insert into containeritemsToCheck[foundIndex].second = num;if (infile.eof()){break;}}infile.close();PrintItems(itemsToCheck);if (CheckAllBeenSet(itemsToCheck) == false){cout << "Error in checking " << MEM_INFO_FILE_NAME << endl;return -1;}// set used memory according to the requirementslong long memToUse = 0;long long freeMemCount = 0;if (isDebugging){cout << "Need memory use in total one ? " << fromTotalMem << endl;}if (!fromTotalMem){if (isDebugging){cout << "Need memory use in free one\n";}freeMemCount = CheckFreeMemInKByte(itemsToCheck);}else{if (isDebugging){cout << "Need memory use in total one\n";cout << "total memory is " << itemsToCheck[MEMTOTAL].second << "KB, that " << itemsToCheck[MEMTOTAL].second * 1024 << "B" << endl;}freeMemCount = itemsToCheck[MEMTOTAL].second;}cout << "Free Mem Count is " << freeMemCount << "KB" << endl;memToUse = freeMemCount * ((double)1 - (double)((double)freePercentage / (double)100) );cout << "MemToUse  is " << memToUse << "KB" << endl;char* memConsumer[1024];int j = 0;for (; j < 1024; j++){memConsumer[j] = NULL;}try{for (j = 0; j < 1024; j++){if (memConsumer[j] == NULL){memConsumer[j] = new char[memToUse];}for (int i = 0; i < memToUse; i++){memConsumer[j][i] = '5';}}}catch(std::bad_alloc){// swallow the exception and continuecout << "no more memory can be allocated, already alloced " << j * memToUse << "B";}while (1){        sleep(2);}return 0;
}