I'm trying to figure out how to write to a file outside the working directory. This is the code I currently have.
#include <iostream>
#include <fstream>
#include <string>
int main()
{
std::string sp{};
std::fstream ss("C:\\Users\\onion\\AppData\\Roaming\\MetaQuotes\\Terminal\\some numbers\\MQL5\\Files\\testnew.txt", std::ios::in | std::ios::out);
if (!ss.is_open()) std::cout << "Failed" << '\n';
else
{
while (ss.is_open())
{
std::getline(ss, sp);
std::cout << sp << '\n';
ss << "new data";
if (ss.eof())break;
}
}
}
I can read the file perfectly fine, but I cant write to it? Could it be that Metatrader itself is limiting my ability to write to a file or does a file have to be in the working directory to be able to write to it? or am I just doing it wrong?
Related
ifstream fin;
fin.open("C:\\Users\\Zach\\Desktop\\input.txt");
if (!fin)
{
cout << "e";
}
e is printing whether I use the full pathway or just input.txt from a resource file
If the file exists, make sure that you have got the path specified correctly. Since you're running on Windows, you can verify the full path to your executable with the following code.
#include <iostream>
#include <fstream>
#include <string>
#include <windows.h>
#define BUFSIZE 4096
std::string getExePath()
{
char result[BUFSIZE];
return std::string(result, GetModuleFileName(NULL, result, BUFSIZE));
}
int main()
{
std::ifstream infile("input.txt");
if (infile.is_open())
{
std::cout << "Success!" << std::endl;
infile.close();
}
else
{
std::cout << "Failed to open input.txt!" << std::endl;
std::cout << "Executable path is ->" << getExePath() << "<-" << std::endl;
}
return 0;
}
This will allow you to verify that your path to the input file is correct, assuming that it's collocated with your executable.
You need to direct output into the ifstream object by using fin << "string"; and not directing to standard out via cout.
I have file (let's call it "file.txt") which is in a folder /folder/where/the/file/is.
And this folder has been exported to $FOLDER, such as if I do :
echo $FOLDER, I got : folder/where/the/file/is
Now, I want to test if the file exists or not.
So, I tried
ifstream ifile(Name_finput);
if(!ifile.good()){
cout << "File doesn't exist !" << endl;
return;
}
This works if Name_finput = "/folder/where/the/file/is/file.txt", but not if Name_finput=$FOLDER/file.txt
Is there a way for it to work by keeping the form $FOLDER/file.txt ?
It seems that the compiler doesn't interpret $FOLDER as /folder/where/the/file/is.
$FOLDER is not valid C++ code. In order to access the environment variables, you need to use std::getenv(). Here's how your code should look:
#include <iostream>
#include <cstdlib>
#include <fstream>
int main() {
std::ifstream ifile;
if (const char* e = std::getenv("FOLDER")) {
ifile.open(std::string(e) + std::string("/file.txt"));
if (!ifile.is_open()) {
std::cout << "File doesn't exist !" << std::endl;
} else {
// Do-stuff with the file
}
}
return 0;
}
I'm trying to open a simple txt.file in c++ (visual studio), but are only triggering "else".
codes.txt is together with the main file in source files and are included. This is more or less how it looks
#include <iostream>
#include <fstream>
int main()
{
std::ifstream file("codes.txt");
if (file.is_open())
{
std::cout << "success" << std::endl;
}
else
{
std::cout << "Unable to open file" << std::endl;
}
}
The txt file did not exist in the folder of the program. Runned perfectly after it was included.
I'm trying to write a program to parse the first and sixteenth columns of a CSV file (converted into .txt). I have the CSV ("posts.txt") document in the folder with the executable. But, whenever I try to run the executable, my program delivers that it cannot open the file (or that "!infile.is_open()"). Mind giving me some assistance? I'm running in Xcode 3.2.3 on Mac OSX 10.8.3. The code is shows below.
#include <iostream>
#include <fstream>
#include <cstdlib>
#include <string.h>
using namespace std;
void answeredPostGrabber()
{
ifstream inFile("posts.txt");
string postNumber;
string answerNumber;
string throwAway;
if(inFile.is_open())
{
while(inFile.good())
{
getline(inFile,postNumber,',');
cout << postNumber << ",";
for(int y=1;y++;y<16)
{
getline(inFile,throwAway,',');
}
getline(inFile,answerNumber,',');
cout << answerNumber << endl;
ofstream edges;
edges.open("edges.txt",ios::app);
edges << postNumber << "," << answerNumber<< endl;
edges.close();
ofstream nodes;
nodes.open("nodes.txt",ios::app);
nodes << postNumber << "\n" << answerNumber << endl;
nodes.close();
getline(inFile,throwAway);
}
}else cout << "ERROR: Unable to open file." << endl;
}
int main ()
{
answeredPostGrabber();
return 0;
}
Thank you in advance!
I have the CSV ("posts.txt") document in the folder with the executable.
The file should be present in the current working directory of your process, which may or may not be the same directory where the executable lives. If in doubt, try specifying the full path in ifstream inFile(...); to see whether that changes things.
Additionally, the file needs to have the correct permissions to ensure that it's readable by the process.
I'm trying to read in a file that contains matrix data into a boost matrix. "" is already supposed to have operator overloads for this sort of thing and I can get it to write to a standard stream (cout). I don't know what's wrong with going the other way. I'm fairly new to C++, so I'm guessing I'm making an incorrect assumption regarding file streams, but it seemed like it made sense. Here are the web pages I'm going on:
http://www.boost.org/doc/libs/1_51_0/boost/numeric/ublas/io.hpp
http://www.cplusplus.com/reference/iostream/ifstream/ifstream/
Here's my code:
using namespace std;
matrix<double> M;
ifstream s("C:\temp\perm.txt", ifstream::in);
s >> M;
s.close();
std::cout << M;
Here's what my file looks like:
[4,4]((0,0,1,0),(0,0,0,1),(0,1,0,0),(1,0,0,0))
Here is a small example, please try it out and see what happens. If this doesn't work, I suspect that the problem is that the file path is wrong or the program is failing to read from the text file:
#include <boost/numeric/ublas/io.hpp>
#include <boost/numeric/ublas/matrix.hpp>
#include <iostream>
#include <fstream>
int main()
{
boost::numeric::ublas::matrix<double> m;
std::ifstream s("C:\temp\perm.txt");
if (!s)
{
std::cout << "Failed to open file" << std::endl;
return 1;
}
if (!s >> m)
{
std::cout << "Failed to write to matrix" << std::endl;
return 1;
}
std::cout << "Printing matrix: ";
std::cout << m;
}