#include <iostream>
#include <fstream>
using namespace std;
int main()
{
fstream dataFile("data1.txt");
if(dataFile.fail())
{
cout<<"Unable to open file"<<endl;
exit(1);
}
double value = 0;
while(dataFile >> value)
cout<<"Read: "<< value << endl;
dataFile.close();
}
The output of this program is always Unable to open file.
please tell me why im not able to make files. im using a mac book pro (IED: coderunner 2) dont know if that makes a difrence
Depending on your IDE, the program might not be running in the location you think it is. Try putting your text file in different locations in the project hierarchy. It's likely that it's not in the right spot.
You need to verify the location of the file first. For example when running your program from a VS IDE you would not place the text file inside a Debug or Release folder. You would place your text file inside a folder from which your IDE launches an executable. If you ran a standalone executable then you would place your txt file in the same folder with the executable.
Since you are using your file for the input and not the output you could use the std::ifstream instead:
std::ifstream dataFile("data1.txt");
You don't have any code that creates a file.
To create a file:
1) Use std::ofstream
2) Use std::fstream with the correct mode.
Although not necessary, you should write data to the file to help create it.
The code in your post is reading from a file. You open a file, and the open may not be successful. You should have your program tell fstream the path to the file (to remove ambiguities).
Related
I want to open and read a file in C++. Therefor I wrote the following code:
#include <fstream>
#include <iostream>
#include <string>
...
string line;
ifstream file;
file.open("./db.config");
if (file.is_open()) {
cout << "File is open" << endl;
getline(file, line);
file.close();
}else cout << "File is not open" << endl;
This code is written in the main.cpp. I verified that main.cpp and db.config are in the same directory.
I don't get any Compiletime oder Runtime Errors. It only prints "File is not open". I also tried it without "./" ( file.open("db.config"); ), but this also didn't work.
The problem is, the current working directory is not the one where db.config file is located. You seem to have it in the same directory as the .cpp file. The current working directory is probably something different. Ultimately you need to decide where you want db.config file to reside, there are many options, but here's simple solution:
See where the application binary is.
Copy db.config there if it isn't there already.
In your code, change to that directory before you load the file, which you can do with Qt like this:
QDir::setCurrent(QCoreApplication::applicationDirPath());
Note that if the user runs the program from command line, and are allowed to give files as arguments, then changing working directory inside the program might make those files not be found. In that case, construct absolute path to db.config instead of changing the working directory.
You could read QStandardPaths docs to get better idea on where you actually want to store the db.config file. This depends on how you plan to distribute the application. If you just want to have it in .zip or something, then same directory with application binary is probably fine.
I'm trying to create a log file using the code below, but It's not working and I'm unable to get the logs as the file is not created!
#include <iostream>
#include <fstream>
using namespace std;
ofstream myfile;
int main () {
myfile.open ("example.txt");
if (!myfile.is_open())
{
cerr << "Failed to create Log" << endl;
}
myfile << "Writing this to a file.\n";
myfile.close();
return 0;
}
For me, it is working fine. compiled with g++ on ubuntu.
If your are using linux, try locating example.txt as may be the working directory is different. In windows, you can search for the file in your computer.
I managed to get your code working, as it worked out of the box. Files created adhere to an odd structure, so you'll need to put your assembly version as a prefix either through a define or a variable.
You can find example.txt up a directory from Debug/Release, next to your .vcxproj file, and in the folder next to your .sln file.
Tinkeroonie is the name of my project, yours might be LoggerTest or something like that.
Highlighted is the folder you need.
I am trying to read in a basic txt file, but I think the programming is not detecting the txt file. Here's my code.
int main() {
ifstream in;
in.open("testing.txt");
if (in.fail()) cout << "fail" << endl;
return 0;
}
The program is printing out fail. I created the txt file by right clicking the project and adding a new empty file. I am completely stuck, so I would appreciate any help.
As from QT Creator's documentation, you can change the working directory where your program should be executed in the project run settings:
If your file exists in a different path than the default (which is where QT Creator builds the executable), you can set it there.
I created the txt file by right clicking the project and adding a new empty file.
That creates the .txt file at your project main path, not where the executable is build actually.
#include <iostream>
#include <fstream>
using namespace std;
int main()
{
ifstream file;
file.open("./cp.txt");
if(file.good())
{
cout << "done!";
}
else
{
cout << "fail";
}
return 0;
}
why does my code can't cp.txt file? it is in project folder. i'm using gnu/linux.
as open i mean the program will open it in some text editor i.e:. leafpad
as open i mean the program will open it in some text editor i.e:. leafpad
That's not going to happen.
When you open an ifstream object it means the file is open for reading by that object, it does not mean a text editor is launched and displays the file!
Maybe what you want is:
system("leafpad cp.txt");
The system function runs another command, in this case it runs the command to launch leafpad with your file as an argument.
Note that the file will be searched for in the current working directory of your program, which is not the same as your "project directory". If you don't know what the current working directory is when your program gets run then you will need to provide an absolute path to the file, not a relative path like cp.txt
you have mentioned having a project folder. if you use an IDE,
it might change the current directory of the running executable.
try deleting the file and creating the file within your code eg:
ofstream ofile;
ofile.open("./cp.txt");
ofile.close();
if you get an output done! then search for the file.
I have created a text file with content. It is located in the same folder as the cpp files. And I have confirmed several times that the file exists. When I run g++, compile and run it finds the file. When I run it in Xcode, it does not work. If fails to find the file.
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
int main () {
string line;
ifstream myfile ("example.txt");
if (myfile.is_open())
{
while ( myfile.good() )
{
getline (myfile,line);
cout << line << endl;
}
myfile.close();
}
else cout << "Unable to open file";
return 0;
}
Your file fails to open because XCode launches from the IDE in the default build location, which is actually a temporary directory off somewhere on your disk. If you want change the working directory at launch-time to something else (like the location where your files can be found):
Select the Product/Edit Scheme... menu option.
Select the Run schema in the left list.
At the bottom Options tab on the right pane should be a "Working Directory" option. Check the checkbox and set the custom working directory to someplace you know (your "/Users/yourname" home directory is a decent place that I use).
Make sure any "current directory" data files you need for your program execution from the IDE are in this directory.
And in case you didn't see it, this is also the place where you can configure command-line arguments (on another tab) of the same dialog.
Try to add files to the project in XCode or use the absolute path instead.