I wrote a code to make "text1.txt" file. It worked correctly, then I've been trying to read from the file, but every time is_open() function doesn't return true. Even so I copied other codes in the way exactly they are in different compilers, but it never works. How will I solve this:(
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
int main() {
ifstream file1("text1.txt");
string str;
if(file1.is_open()){
while(getline( file1, str)){
cout<<str;
}
}
else
cout<<"the file is not open"<<endl;
return 0;
}
How are you running your program?
The most common cause of this I've seen is that you're running your program inside an IDE (like Visual Studio), and your current directory isn't where you think it is.
Try putting in the full path to the file and see if your problem disappears.
Related
I have two similar methods that open a file identically, but process them and return values a bit differently, yet while the first method does that successfully, the second method, which is called after the first one, fails.
I have tried changing the path to this file, its extension, but I think I miss some important knowledge about ifstream.
vector<User> Database::createUserDatabase()
{
vector<User> users;
ifstream inputFile;
inputFile.open(pathToFile, ios::in);
//Some file processing
inputFile.close();
return users;
}
And that works perfectly, while
vector<User> Database::createBookDatabase()
{
vector<Book> books;
ifstream inputFile;
inputFile.open(pathToFile, ios::in);
//Some file processing
inputFile.close();
return books;
}
fails to end whenever I check if the file has been opened or not using
inputFile.is_open()
These functions are defined in class files Database.cpp, User.cpp, Book.cpp, which are correctly linked to the main.cpp with the following content:
#include <iostream>
#include <cstdlib>
#include <string>
#include <cstring>
#include <sstream>
#include <vector>
#include <fstream>
#include "../lib/Book.h"
#include "../lib/User.h"
#include "../lib/Database.h"
using namespace std;
int main()
{
Database userDatabase("../database/users.txt", "users");
Database bookDatabase("../database/lmsdb.txt", "books");
vector<User> users = userDatabase.createUserDatabase();
vector<Book> books = bookDatabase.createBookDatabase();
return 0;
}
Here are my Project directories
Using gdb debugger, I have confirmed that the file is not being opened at all. I assume that I did not close the files properly, but I have a little knowledge of C++ yet (been learning it for only a week or so).
Looking forward to see what you can suggest reading/researching, yet I really would like to see a straightforward solution to this problem.
I assume that I did not close the files properly, [..]
Yes, but that probably isn't the cause of the issue. The C++ way is to not close them explicitly. Due to RAII, the ifstream will close itself once it goes out of scope (i.e. when the enclosing function terminates).
There are many reasons why a file could fail to open, including:
It doesn't exist.
Trying to open a read-only file in write mode.
The file is in use by another process. (Maybe you have it opened in an editor?)
Insufficient privileges (e.g. due to the file being protected).
I'm writing simple console application in cpp but none of my approaches to write it were succesful. I'm trying to read row after row from ifstreamed file until the file ends.
#include <string>
#include <fstream>
#include <iostream>
using namespace std;
void lowtempbin(string inpfile){
ifstream wyciag(inpfile.c_str());
string row_temp_bin;
int i=0;
while(getline(wyciag, row_temp_bin)){
i++;
cout<<i;
}
}
int main(){
lowtempbin("danesystemy.txt");
return 0;
}
Why the program doesn't enter while loop, and if getline does load nothing, then whole function should return 0? And then code after while is executed (not inside). I'll add that I pass as the argument to lowtempbin()inside main, name of the file that is in the same directory as executable (in code:blocks /project/bin/Debug). Also when I debug the application, while loop is never executed, as if getline returns negative value.
Code shoud cout all numbers, one for every row, but it just returns 0;
The program compiles and produces the expected result when ran.
Your problem seems to be one of the following:
The filename is incorrect.
The file is not in the same directory as the executable.
The file doesn't exist at all.
I have a program that reads in a file. All my classes compile fine, but there seems to be an error when I read in the file. Eclipse shows an empty string is being read in (""), which is not what I want.
I have the code for my main below with a while loop. I placed the loop just to see how it would run when debugging, and it runs an infinite loop since it is always reading in "", and never reaches end of file. I have put the file in the working directory and every other folder just to be sure, but it is always doing this even though the file is full of strings and integers. Is there anything I am doing wrong here?
#include "Translator.h"
#include <iostream>
#include <fstream>
#include <cstdlib>
#include <string>
using namespace std;
int main(int argc, char* argv[])
{
ifstream readFile;
readFile.open("sample.html");
while (!readFile.eof()) // for debugging purposes only
{
string x;
readFile >> x; // x is "" everytime through the loop
readFile >> x; // x is also ""
}
Translator t(readFile);
readFile.close();
return 0;
}
My guess is that your file did not actually open, and the eof bit was therefore not set. You never test whether the file was opened successfully. It could be that your working directory is not what you think it is, or the file is locked by another process (perhaps open in a text editor).
Officially, you can test readFile.fail() after you try opening.
I've found that checking readFile.good() is fine too - in fact you can use that as your loop condition.
I prefer the positive message of 'good' in my code, rather than the potentially upsetting 'fail'.
You should also test your stream as WhozCraig suggested in comments, when you are reading data. You cannot assume that the operation was successful. If it fails for reasons other than EOF, you need to know.
For these reasons, don't use readFile.eof() as your loop condition.
I'm doing the stanford course cs106b in C++, and I'm stuck and I can't seem to get it right. This probably a very easy fix for someone who knows this kind of stuff.
I have three files, one main.cpp and a randword.h and randword.cpp. In randword.h I have #include "simpio.h" which is a stanford library where GetLine() is defined. I can get GetLine() to work in the main.cpp file but when I try to compile I get "undefined reference to 'GetLine()'" in randword.cpp.
I use codeblocks and I have used the "Add files..." function.
Here's the code for main.cpp:
#include "randword.h"
/* Private function prototypes */
/* Main program */
randword rw;
int main() {
rw.initDictionary();
}
randword.h:
#ifndef RANDWORD_H_INCLUDED
#define RANDWORD_H_INCLUDED
#include <iostream>
#include <fstream>
#include <stdio.h>
#include "simpio.h"
#include "strutils.h"
using namespace std;
class randword{
public:
void initDictionary();
string chooseRandomWord();
string strArray[];
private:
};
#endif // RANDWORD_H_INCLUDED
random.cpp:
#include "randword.h"
using namespace std;
void randword::initDictionary(){
string fileName;
ifstream infile;
fileName = GetLine();
infile.open(fileName.c_str());
if(infile.fail()) cout << "Couldn't read file.";
return;
}
string randword::chooseRandomWord(){
string st1;
return st1;
}
Any help would be much appreciated! I suspect that this question was already posted, but I couldn't find it. Thanks!
try adding the library manually using code blocks
Open up your project
Right click your project and select build options..
select debugger
Go to linker settings
Under Link Librarys click "add"
Find your lib file, select it and keep as a relative path
Your project SHOULD run, if not reply here(as i explained something wrong)
randword.cpp does NOT have the library file needed to use GetLine, you may have included it inside your header file, but this does not carry over to randword.cpp. You need to include the library file just as you would in any other file in order to have access to it's functions.
//randword.cpp
#include <iostream>
#include "simpio.h" //include again!!!
//code here....
I have really strange problem. In Visual C++ express, I have very simple code, just:
#include <fstream>
using namespace std;
int main()
{
fstream file;
file.open("test.txt");
file<<"Hello";
file.close();
}
This same code works OK in my one project, but when I create now project and use this same lines of code, no file test.txt is created. Please, what is wrong?ยจ
EDIT: I expect to see test.txt in VS2008/project_name/debug - just like the first functional project does.
Canonical code to write to a file:
#include <fstream>
#include <iostream>
using namespace std;
int main() {
ofstream file;
file.open("test.txt");
if ( ! file.is_open() ) {
cerr << "open error\n";
}
if ( ! ( file << "Hello" ) ) {
cerr << "write error\n";
}
file.close();
}
Whenever you perform file I/O you must test every single operation, with the possible exception of closing a file, which it is not usually possible to recover from.
As for the file being created somewhere else - simply give it a weird name like mxyzptlk.txt and then search for it using Windows explorer.
Perhaps the executable is run in a different directory than it was before, making test.txt appear somewhere else. Try using an absolute path, such as "C:\\Users\\NoName\\Desktop\\test.txt" (The double backslashes are needed as escape characters in C strings).
fstream::open() takes two arguments: filename and mode. Since you are not providing the second, you may wish to check what the default argument in fstream is or provide ios_base::out yourself.
Furthermore, you may wish to check whether the file is open. It is possible that you do not have write permissions in the current working directory (where 'test.txt' will be written since you don't provide an absolute path). fstream provides the is_open() method as one way of checking this.
Lastly, think about indenting your code. While you only have a few lines there, code can soon become difficult to read without proper indentation. Sample code:
#include <fstream>
using namespace std;
int main()
{
fstream file;
file.open("test.txt", ios_base::out);
if (not file.is_open())
{
// Your error-handling code here
}
file << "Hello";
file.close();
}
You can use Process Monitor and filter on file access and your process to determine whether the open/write is succeeding and where on disk it's happening.
Theres two ways to fix this. Either do:
file.open("test.txt", ios::out)
#include <fstream>
using namespace std;
int main()
{
fstream file;
file.open("test.txt", ios::out);
file<<"Hello";
file.close();
}
Or you can create an ofstream instead of fstream.
#include <fstream>
using namespace std;
int main()
{
ofstream file;
file.open("test.txt");
file<<"Hello";
file.close();
}