Ifstream does not read the EOF character

Question

I am creating a program (in C ++) that takes an ASCII file and reads several values ​​from each line until it reaches the end of the file. I use ifstream to read a file and I never had a problem stopping it when I use the ifstream.eof() method. However, this time, although he found the eof character in my test case, when I parsed my other files, this is an endless loop because it never finds the eof character. Is this a problem with the encoding or a problem with my files?

 string line = ""; unsigned long pos = 0; ifstream curfile(input.c_str()); getline(curfile, line); int linenumber = 0; cout<<"About to try to read the file"<<endl; if (!curfile.good()) cout<<"Bad file read"<<endl; while (!curfile.eof()) { cout<<"Getting line "<<linenumber<<endl; linenumber++; pos = line.find_first_of(' '); line = line.substr(pos+1, line.size()-1); pos = line.find_first_of(' '); current.push_back(atof(line.substr(0, pos).c_str())); for (int i = 0; i<4; i++) { pos = line.find_first_of(' '); line = line.substr(pos+1, line.size()-1); } pos = line.find_first_of(' '); dx.push_back(atof(line.substr(0, pos).c_str())); pos = line.find_first_of(' '); line = line.substr(pos+1, line.size()-1); pos = line.find_first_of(' '); dy.push_back(atof(line.substr(0, pos).c_str())); getline(curfile, line); } 

EDIT: When I first run the loop, currentfile.good () returns false ... what am I doing that causes it to return this?

Answer 1

First of all, you should not check like that. eof() does not return true until after it is read. But you can do better (and easier)!

check the state of a stream with an implicit conversion to void* , which can be used in a bool context . Since most read operations in streams return a reference to the stream, you can write very consensus code as follows:

 std::string line; while(std::getline(currentfile, line)) { // process line } 

Basically, what he does is say, "while I was able to successfully extract the string from the currentfile , do the following", which you really wanted to say anyway; -);

As I said, this applies to most stream operations, so you can do things like this:

 int x; std::string y; if(std::cin >> x >> y) { // successfully read an integer and a string from cin! } 

EDIT . I would rewrite your code like this:

 string line; unsigned long pos = 0; int linenumber = 0; ifstream curfile(input.c_str()); std::cout << "About to try to read the file" << std::endl; while (std::getline(curfile, line)) { std::cout << "Getting line " << linenumber << std::endl; linenumber++; // do the rest of the work with line } 

Answer 2

Do not do it like this.

EOF is not the only thing you will encounter while reading. There are a bunch of bugs there, and it’s best to just test the stream itself:

 while(currentfile) { // read somehow } 

If you are reading the lines, then the easiest way:

 std::string line; while(std::getline(currentfile, line)) { // use line } 

Answer 3

Your first getline call fires one of the crash bits in the ifstream object. Therefore, if you perform a failure check using ios::good() , you never enter your read loop. I would see what the value of line ... it is probably empty, which means that you have another problem reading your file, for example, permission problems, etc.

Answer 4

The problem is here:

 if (!curfile.good()) cout<<"Bad file read"<<endl; // OK you print bad. while (!curfile.eof()) // But the loop is still entered. // Another reason to **NEVER** to use // while (file.eof()) // as bad does not mean eof // though eof is bad 

Try the following:

 void readFile(std::istream& str) { std::string line; while(std::getline(str, line)) { std::stringstream lineStream(line); std::string ignoreWord; int number[3]; lineStream >> ignoreWord // reads one space seporated word >> number[0] // reads a number >> ignoreWord >> ignoreWord >> ignoreWords // reads three words >> number[1] // reads a number >> number[2]; // reads a number current.push_back(number[0]); dx.push_back(number[1]); dy.push_back(number[2]); } }