I/O operation, file operation behaviou
Please see the following program. My intention is to open the file
(create it if it does not exist), or if the file exists already it
should be truncated (the entire contents is thrown away) and over
written. "Create if does not exists works fine", What is wrong with
the truncating part ?. fd.is_open returns false always.
#include <iostream>
#include <fstream>
#include <string>
#include <set>
using namespace std;
class CFileXP {
public:
void open(std::string type);
void close(string method);
private:
std::set< string> openFiles;
std::string fileName;
std::string type;
};
void CFileXP::open(std::string _type)
{
set< string>::iterator it;
type = _type;
fileName = "C:\\temp\\" + type + "XML.xml";
std::fstream fd;
it = openFiles.find(type);
if (it == openFiles.end()) {
openFiles.insert(type);
fd.open(fileName.c_str(), ios::out | ios::trunc);
if (fd.is_open()) {
cout << "File is opened now\n";
}
fd << "<" + type + "S>" + "\r\n";
}
fd.close();
}
void CFileXP::close(string method)
{
set< string>::iterator it;
std::fstream fd;
for (it = openFiles.begin(); it != openFiles.end(); it++) {
fileName = "C:\\temp\\" + *it + "XML.xml";
fd.open(fileName.c_str(), ios::out | ios::app);
fd << "</" + *it + "S>" + "\r\n";
fd.close();
}
openFiles.erase(openFiles.begin(), openFiles.end());
}
int main()
{
CFileXP file;
file.open("MYTPE");
}