Reading from file C++

Question

I need to read this txt file but I don't understand what I'm doing wrong? http://pastebin.com/gPVbuvhb Here's my reading function

void Read(School & snew){ string school, name, group; Student S; ifstream fd(CD); getline(fd, school, ';'); S.SetSchool(school); cout << S.GetSchool() << endl; while(!fd.eof()){ getline(fd, name, ','); fd >> ws; getline(fd, group, ' '); int Paz[Student::M]; int kiek = 0; while(fd.peek()!= '\n' && !fd.eof()){ fd >> Paz[kiek++]; } fd.ignore(); } fd.close(); }

Here's my Student class

class Student{ public: static const int M = 5; private: string school, name, group; int *Marks; // dynamic array of student marks int nmax; // max size of array int n; // current size of array void IncreaseCapasity(int kiek); public: Student(int nmax = 0); ~Student(); void SetMarks(int mark); void SetSchool(string school); void SetName(string name); void SetGroup(string group); int GetMark(int i){return Marks[i];} string GetSchool(){return school;} string GetName(){return name;} string GetGroup(){return group;} int GetN(){return n;} }; Student::Student(int nmax):Marks(NULL), n(n), nmax(nmax){ if(nmax > 0){ Marks = new int[nmax]; } } Student::~Student(){ if(Marks){ delete [] Marks; Marks = NULL; } } void Student::IncreaseCapasity(int kiek){ // maybe this function is incorrect? if(kiek > nmax){ // if array increasing int *SNew = new int [kiek]; for(int i=0; i<n; i++) SNew[i] = Marks[i]; delete [] Marks; Marks = SNew; nmax = kiek; }if(kiek < nmax){ // if array decreasing int *SNew = new int [kiek]; for(int i=0; i<kiek; i++) SNew[i] = Marks[i]; delete [] Marks; Marks = SNew; n = nmax = kiek; } } void Student::SetMarks(int mark){ if(n == nmax) IncreaseCapasity(n + M); Marks[n] = mark; n++; } void Student::SetSchool(string school){ this->school = school; } void Student::SetName(string name){ this->name = name; } void Student::SetGroup(string group){ this->group = group; }

when I'm reading int values fd >> Paz[kiek++]; I get this error Unhandled exception at 0x571121F8 (msvcp110d.dll) in ConsoleApplication1.exe: 0xC0000005: Access violation reading location 0x0000000D.

If you follow "normal" coding conventions we'll all find it much easier to read your code. Use descriptive variable names and start them with a lowercase letter. e.g. student instead of S. Also: what is CD? — John3136
– John3136, Commented Mar 1, 2014 at 10:02
For one, you're checking for success or failure on exactly zero of your IO operations. And your usage of eof() as your loop conditional is wrong. — WhozCraig
– WhozCraig, Commented Mar 1, 2014 at 10:04
You use getline with the delimiter argument of ';'. There's no ; character in the file, so the very first getline sees it as one big line and reads it all. There's nothing left for subsequent getlines. — n. m. could be an AI
– n. m. could be an AI, Commented Mar 1, 2014 at 10:04
I just have edited my code. I dont understand why I get Access violation reading location error. I think with my function IncreaseCapasity is something wrong (but I'm not sure). I checked all my code, and still I can't understand why I get this silly error? — David
– David, Commented Mar 1, 2014 at 10:36

LihO · Accepted Answer · 2014-03-01 10:16:05Z

getline(fd, school, ';');

reads from the fd stream, stopping at first occurence of ';'. Since there is no ';' in your file, it reads whole file into school string.

What you actually want to do is to parse your file line by line, constructing instance of istringstream using each line:

std::string line; while (std::getline(fd, line)) { if (line.empty()) continue; std::istringstream is(line); std::string name, group; if (std::getline(is, name, ',') && std::getline(is, group, ',')) { std::cout << "Name: " << name << " Group: " << group << std::endl; } }

just don't forget to #include <sstream>.

Also note that:

while (!fd.eof()) { std::getline(...); // relying on getline call being successful here }

is not safe, just use its return value directly.

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