I'm trying to make a program that prints all the numbers from 100-999. After that you get to choose how many numbers you want to find. Then you type the number's position and it will be outputed.
There is one problem. The string, named str, stops storing at the number 954.
Here's the code:
#include <iostream>
#include <string>
#include <fstream>
using namespace std;
int main()
{
//Prints to myFile the numbers from 100 to 999 without a space in between. Like this: 100101102...999
ofstream myFile("numere.txt");
for(int i = 100; i <= 999; i++)
myFile << i;
//Makes the string str to store the line: 100101102103...999. But only stores until 954 (100101102..954)
ifstream myFileRead("numere.txt");
string str;
while(getline(myFileRead, str))
cout << str << endl;
//Ouputs the lenght that should be 2700 but is instead 2565
cout << endl;
cout << "String legth: " << str.size() << endl;
cout << endl;
int n, k;
cout << "Enter how many numbers do you want to find: ";
cin >> n;
for(int i = 1; i <= n; i++){
cout << "Enter number position(it starts from 0) : ";
cin >> k;
cout << "Here's the number on position " << k << ": " << str.at(k);
cout << endl;
}
system("pause>0");
}
Thanks for your attention. I’m looking forward to your reply.
C++ streams are buffered. When you use << to write to a file it is not immediately written to the file.
Try to close or flush the ofstream before you read from it:
myFile.close(); // or...
myFile.flush();
For more details I refer you to flush() and close().
PS: Actually it is rather rare that you need to close a fstream explicitly. You wouldn't need to do it when you used seperate functions for writing and reading:
void write_to_file() {
std::ofstream myFile("numere.txt");
//...
}
void read_from_file() {
std::istream myFile("numere.txt");
//...
}
Because the destructor of ofstream already closes the file.
Related
I have a task in C++ to read from a UTF-8 text file, count the characters, and save the character + count in a tsv.
I use everywhere wstring, wifstream, and wofstream.
In the terminal, there are many empty spaces when checking everything, but when outputting to tsv everything is overall fine except for 3 things.
‘ when saved appears as nothing, but its amount is counted correctly.
From nowhere ā and € appear. They are counted as the same amount, but they are not present in the original text at all.
What might be the cause of these issues?
The code is a bit crude but looks like this currently
#include <iostream>
#include <algorithm>
#include <fstream>
#include <vector>
using namespace std;
int main()
{
vector <wchar_t> characters;
vector <int> counter;
string filename;
string param;
cout << "Please input the filename: ";
cin >> filename;
cout << "Please, if you want to convert everything to lowercase, input 'lower', else input 'No': ";
cin >> param;
wifstream inFile;
wofstream endFile("dancing_men_char_frequency.tsv");
inFile.open(filename);
wstring Tfile;
int checker;
//inFile >> Tfile;
while(getline(inFile, Tfile)) {
//wcout << Tfile;
//sort(Tfile.begin(), Tfile.end());
if(param == "lower"){
transform(
Tfile.begin(), Tfile.end(),
Tfile.begin(),
towlower);
}
for(int i = 0; i < Tfile.length(); i++){
if(find(characters.begin(), characters.end(), Tfile[i]) != characters.end())
{
if(isblank(Tfile[i])){}else{
checker = 0;
while(characters[checker] != Tfile[i]){
checker++;
}
counter[checker] += 1;
}
}else{
if(isblank(Tfile[i])){}else{
characters.push_back(Tfile[i]);
counter.push_back(1);
}
}
}
}
int sum = 0;
for(int i = 0; i < characters.size(); i++){
wcout << characters[i] << " ";
cout << counter[i] << " " << i << endl;
sum += counter[i];
endFile << characters[i] << '\t' << counter[i] << '\n';
}
cout << sum << endl;
//wcout << Tfile;
//sort(Tfile.begin(), Tfile.end());
//wcout << Tfile;
endFile.close();
inFile.close();
return 0;
}
I have some code that takes a list of names + double values from a .txt file and displays these in the command prompt. For this an array of structs is dynamically allocated. The code should know the size of the array based on the first value in the .txt file, which is then followed by the names and associated values. It should then display the list in two parts with names that have an associated double value higher than or equal to 10.000 listed first. If none of the values qualifies, it displays 'None' in the first half.
The program executes, but the debugger gives an exception and the output is not as expected.
#include <iostream>
#include <fstream>
#include <string>
#include <cstdlib>
using namespace std;
struct donor
{
string name;
double contribution = 0;
};
int main()
{
string filename;
ifstream inFile;
cout << "Enter name of data file: ";
cin >> filename;
inFile.open(filename);
cin.clear();
if(!inFile.is_open())
{
cout << "Could not open the file " << filename << endl;
cout << "Program terminating.\n";
exit(EXIT_FAILURE);
}
int amount;
inFile >> amount;
cin.clear();
donor* dlist = new donor[amount];
int i;
while(inFile.good())
{
for(i = 0; i < amount; i++)
{
getline(inFile, dlist[i].name);
cin.clear();
inFile >> dlist[i].contribution;
cin.clear();
}
}
cout << "Here's the list of Grand Patrons:\n";
bool grandpatrons = false;
for(i = 0; i < amount; i++)
{
if(dlist[i].contribution >= 10000)
{
grandpatrons = true;
cout << dlist[i].name << endl;
cout << dlist[i].contribution << endl;
}
}
if(grandpatrons == false)
{
cout << "None" << endl;
}
cout << "Here's the list of Patrons:\n";
for (i = 0; 1 < amount; i++)
{
if (dlist[i].contribution < 10000)
{
cout << dlist[i].name << endl;
cout << dlist[i].contribution << endl;
}
}
delete[] dlist;
return 0;
}
The donorlist.txt file looks like this:
4
Bob
400
Alice
11000
But the output looks like this:
Enter name of data file: donorlist.txt
Here's the list of Grand Patrons:
None
Here's the list of Patrons:
0
0
0
0
The exception that the debugger gives me is:
Exception thrown at 0x5914F3BE (ucrtbased.dll) in 6_9.exe: 0xC0000005: Access violation reading location 0xA519E363.
Now I assume something is going wrong with reading from the dynamically allocated memory. Maybe something is causing me to read from memory beyond the allocated array? I'm having trouble finding exactly where the mistake is being made.
Your problems begin with the wrong amount written in your data file.
Fix it with:
2
Bob
400
Alice
11000
They then continue with the fact that you inccorectly read the file.
Remember: Mixing operator>> and getline() is not as simple as it seems.
You see, operator>> IGNORES newline and space characters until it finds any other character.
It then reads the upcoming characters until it encounters the next newline or space character, BUT DOES NOT DISCARD IT.
Here is where the problem with getline comes in. getline reads EVERYTHING until it encounters newline or a specified delim character.
Meaning, that if your operator>> stops after encountering newline, getline will read NOTHING since it immediately encounters newline.
To fix this, you need to dispose of the newline character.
You can do this by first checking if the next character in the stream is indeed newline and then using istream::ignore() on it;
int next_char = stream.peek();
if(next_char == '\n'){
stream.ignore();
}
A working example of your code would be:
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
//Suggestion: class/struct names should start with a capital letter.
struct Donor{
//Suggestion: Use member initializer lists to specify default values.
Donor() : name(), contribution(0){}
string name;
double contribution;
};
int main(){
cout << "Enter the filename: ";
string filename;
cin >> filename;
//Suggestion: Open the file immediately with the filename and use `operator bool` to check if it opened.
ifstream inFile(filename);
if(!inFile){
cout << "Could not open the file " << filename << '\n';
cout << "Program terminating.\n";
exit(EXIT_FAILURE);
}
int amount;
inFile >> amount; //! Leaves '\n'
Donor* donors = new Donor[amount];
for(int i = 0; i < amount; ++i){
switch(inFile.peek()){
case '\n': inFile.ignore();
break;
case EOF: cout << "Donor amount too big!\n";
exit(EXIT_FAILURE);
}
getline(inFile, donors[i].name);
inFile >> donors[i].contribution;
}
cout << "Here's the list of Grand Patrons:\n";
bool grandpatrons_exist = false;
for(int i = 0; i < amount; ++i){
if(donors[i].contribution >= 10000){
grandpatrons_exist = true;
cout << donors[i].name << '\n';
cout << donors[i].contribution << '\n';
}
}
if(!grandpatrons_exist){
cout << "None\n";
}
cout << "Here's the list of Patrons:\n";
for(int i = 0; 1 < amount; ++i){
if(donors[i].contribution < 10000){
cout << donors[i].name << '\n';
cout << donors[i].contribution << '\n';
}
}
delete[] donors;
return 0;
}
Now, an even better solution would be to use vectors instead of raw pointers and implement operator>> and operator<< which would greatly simplify
the reading and printing of the objects.
#include <iostream>
#include <fstream>
#include <string>
#include <vector>
#include <algorithm>
using namespace std;
class Donor{
public:
Donor() noexcept: name(), contribution(0){}
friend istream& operator>>(istream& stream, Donor& donor){
switch(stream.peek()){
case EOF: return stream;
case '\n': stream.ignore();
}
getline(stream, donor.name);
stream >> donor.contribution;
return stream;
}
friend ostream& operator<<(ostream& stream, const Donor& donor){
stream << donor.name << ' ' << donor.contribution;
return stream;
}
const string& get_name() const noexcept{
return name;
}
const double& get_contribution() const noexcept{
return contribution;
}
private:
string name;
double contribution;
};
int main(){
cout << "Enter the filename: ";
string filename;
cin >> filename;
ifstream inFile(filename);
if(!inFile){
cout << "Could not open the file " << filename << '\n';
cout << "Program terminating.\n";
exit(EXIT_FAILURE);
}
int amount;
inFile >> amount;
vector<Donor> donors(amount);
//Read it as `for donor in donors`
for(Donor& donor : donors){
inFile >> donor;
}
//An STL function that takes a lambda as the thirs argument. You should read up on them if you haven't.
//I would prefer using this since it greatly improves readability.
//This isn't mandatory, your implementation of this part is good enough.
bool grandpatrons_exist = any_of(begin(donors), end(donors), [](const Donor& donor){ return donor.get_contribution() >= 10000; });
cout << "Here's the list of Grand Patrons:\n";
if(grandpatrons_exist){
for(const Donor& donor : donors){
if(donor.get_contribution() >= 10000){
cout << donor << '\n';
}
}
}
else{
cout << "None\n";
}
cout << "\nHere's the list of Patrons:\n";
for(const Donor& donor : donors){
if(donor.get_contribution() < 10000){
cout << donor << '\n';
}
}
return 0;
}
Some other great improvements would be:
Use partition to seperate great patrons from normal ones.
Use stream iterators to read the objects into the vector.
int main(){
cout << "Enter the filename: ";
string filename;
cin >> filename;
ifstream inFile(filename);
if(!inFile){
cout << "Could not open the file " << filename << '\n';
cout << "Program terminating.\n";
exit(EXIT_FAILURE);
}
//Ignore the first line completely
inFile.ignore(numeric_limits<streamsize>::max(), '\n');
//Calls `operator>>` internally
vector<Donor> donors(istream_iterator<Donor>{inFile}, istream_iterator<Donor>{});
auto first_grand_patron = partition(begin(donors), end(donors), [](const Donor& donor){ return donor.get_contribution() >= 10000; });
cout << "Here's the list of Grand Patrons:\n";
if(first_grand_patron == begin(donors)){
cout << "None!\n";
}
for(auto patron = begin(donors); patron != first_grand_patron; ++patron){
cout << *patron << '\n';
}
cout << "\nHere's the list of Patrons:\n";
for(auto patron = first_grand_patron; patron != end(donors); ++patron){
cout << *patron << '\n';
}
return 0;
}
Now some general tips:
Struct/Class names should start with a capital letter.
Stop Using std::endl.
No need to cin.clear(). Cin is only used once and never again.
Use member-initializer lists.
Optionally use ++i instead of i++ in for loops to get used to the correct way of incrementing a variable unless needed otherwise.
bool grandpatrons is too much of an abstract name for a flag.
donors is a subjectively better name than short for donor list.
my text file was like
123456123456
Jason
uk
012456788
1000
456789456789
david
uk
012456788
1000
i'm trying to get the data from a text file and save it into arrays
however when i want to store the data from the text file into array it loop non-stop.
what should i do ?
the problem exiting in looping or the method i get the data from text file ?
code:
#include <iostream>
#include <fstream>
using namespace std;
typedef struct {
char acc_no[12];
char name[30];
char address[50];
char phone_no[12];
double balance;
} ACCOUNT;
//function prototype
void menu();
void read_data(ACCOUNT record[]);
int main() {
ACCOUNT record[31]; //Define array 'record' which have maximum size of 30
read_data(record);
}
//--------------------------------------------------------------------
void read_data(ACCOUNT record[]) {
ifstream openfile("list.txt"); //open text file
if (!openfile) {
cout << "Error opening input file\n";
return 0;
} else {
int loop = -1; //size of array
cout << "--------------Data From File--------------"<<endl;
while (!openfile.eof()) {
if (openfile.peek() == '\n')
openfile.ignore(256, '\n');
openfile.getline(record[++loop].acc_no, 12);
openfile.getline(record[loop].name, 30);
openfile.getline(record[loop].address, 50);
openfile.getline(record[loop].phone_no, 12);
openfile >> record[loop].balance;
}
openfile.close(); //close text file
for (int i = 0; i <= loop + 1; i++) {
cout << "Account " << endl;
cout << "Account No. : " << record[i].acc_no << endl;
cout << "Name : " << record[i].name << endl;
cout << "Address : " << record[i].address << endl;
cout << "Phone Number : " << record[i].phone_no << endl;
cout << "Balance : " << record[i].balance << endl;
}
}
}
UPDATE:
The OP didn't properly cite the correct format in his data file. This answer is only valid up until the last iteration.
Don't use .eof() - that's more applicable to when you want to open the file and read it by characters.
A better way would be to use the insertion operator >> as follows:
#define ARR_SIZE 31
ACCOUNT temp;
ACCOUNT record[ARR_SIZE];
int i=0;
while(i < ARR_SIZE) {
openfile >> temp.acc_no >> temp.name >> temp.address >> temp.phone_no >> temp.balance;
record[i] = temp;
i++;
}
Of course, even better is to use std::string to hold the values from the input file, in addition to using std::vectors instead of arrays.
The program works all the way up until it checks for the name the user enters. When you enter the name you wish to search for in the array of structures that have been imported from a file full of customer info) it comes back segmentation fault core dumped. This puzzles me.
#include <iostream>
#include <string>
#include <fstream>
#include <cstring>
using namespace std;
struct AccountsDataBase{
char name[50];
string email;
long int phone;
string address;
};
#define MAX 80
AccountsDataBase * account = new AccountsDataBase[MAX];
void readIn(ifstream& file){
int i=0;
while(!file.eof()){
file >> account[i].name >> account[i].email >> account[i].phone >> account[i].address;
}
}
void getAccount(){
char userPick[50];
char streamName[50];
cout << " What account will we be using? " << endl;
cin.getline(streamName, 50);
for(int i=0; strcmp(account[i].name, streamName)!=0; i++){
if( strcmp(account[i].name, streamName)==0){
cout << "\n\n FOUND IT!! \n\n";
cout << account[i].name << "\n" << account[i].email << "\n" << account[i].phone << "\n" << account[i].address << endl;
}
}
}
int main(){
ifstream file;
file.open("2.dat"); //opens data account records text
readIn(file);
getAccount();
delete account;
return 0;
}
Your loop keeps reading everything into the initial element of the array:
while(!file.eof()){
file >> account[i].name >> account[i].email >> account[i].phone >> account[i].address;
}
because the value of i is never incremented. You can convert this to a for loop, like this:
for (count = 0 ; count < MAX && !file.eof() ; count++) {
file >> account[count].name >> account[count].email >> account[count].phone >> account[count].address;
}
Note that I changed i to count:
AccountsDataBase * account = new AccountsDataBase[MAX];
int count = 0;
This will help you solve another problem - determining when the array ends in the getAccount function. Currently, you assume that the record is always there, so the outer loop keeps going on. Now that you have count, you could change the loop like this:
for(int i=0; i < count && strcmp(account[i].name, streamName)!=0; i++){
if( strcmp(account[i].name, streamName)==0){
cout << "\n\n FOUND IT!! \n\n";
cout << account[i].name << "\n" << account[i].email << "\n" << account[i].phone << "\n" << account[i].address << endl;
break;
}
}
if (i == count) {
cout << "Not found." << endl;
}
I have got an input file with following data
2
100
2
10 90
150
3
70 10 80
Now, I am able to read till 4th line ( 10 90) but when reading 5th line(150), the file pointer seems to be stuck at 4th line. I have tried infile.clear() just incase. How do I make sure that file pointer is moving correctly or position it at next line? Appreciate your feedback.
-Amit
#include <iostream>
#include <fstream>
#include <string>
#include <sstream>
using namespace std;
int main(void) {
int cases;
int total_credit=0;
int list_size=0;
string list_price;
//Read file "filename".
ifstream infile;
infile.open("A-large-practice.in",ifstream::in);
if(!infile.is_open()) {
cout << "\n The file cannot be opened" << endl;
return 1;
}
else {
cout<<"Reading from the file"<<endl;
infile >> cases;
cout << "Total Cases = " << cases << endl;
int j=0;
while (infile.good() && j < cases) {
total_credit=0;
list_size=0;
infile >> total_credit;
infile >> list_size;
cout << "Total Credit = " << total_credit << endl;
cout << "List Size = " << list_size << endl;
//cout << "Sum of total_credit and list_size" << sum_test << endl;
int array[list_size];
int i =0;
while(i < list_size) {
istringstream stream1;
string s;
getline(infile,s,' ');
stream1.str(s);
stream1 >> array[i];
//cout << "Here's what in file = " << s <<endl;
//array[i]=s;
i++;
}
cout << "List Price = " << array[0] << " Next = " << array[1] << endl;
int sum = array[0] + array[1];
cout << "Sum Total = " << sum << endl;
cout <<"Testing" << endl;
j++;
}
}
return 0;
}
The problem is that you're using ' ' (space) as your "line terminator" for getline. So when you're reading the numbers on line 4 into the string s, the first one will be "10" and the second will be "90\n150\n3\n70" -- that is, everything up to the next space. This is almost certinaly not what you want and is leading to your confusion about where you are in the file. The next number you read will be 10, leading you to think you're on line 4 when in fact you're on line 7.
edit
The easiest way to fix this is probably to not use getline at all and just read ints directly from the input:
while (i < list_size)
infile >> array[i++];
This ignores the newlines altogether, so the input might as well be all on one line or split between lines randomly, but as you have an initial number that tells you how many numbers to read, that's just fine.