Using getline to read from file to a 2d string array - c++

I am trying to read the contents of a text file into a 2D string array, but no matter what I have tried or searched, I can not find a solution. The code is supposed to load a text file separate it into elements by finding horizontal tabs and display the output. When I run the code as is, I receive an error that I found out from searching online, means that I'm trying to manipulate memory I shouldn't be. I'm not asking for the code to be written, just a push in the right direction. Thank you in advance.
this is what I get when I run the program:
0x23fd5c
Process returned -1073741819 (0xC0000005) execution time : 2.344 s
Press any key to continue.
EDIT:: I have corrected the code so it now functions as it should, but it is not storing the last entry of each line in the text file correctly. I can somehow display the number 100 which is the last entry, but when I try to pass that location or display just playList[0][5] , it says it is equal to the first entry of the next line. Any help would be amazing I posted the current code below.
here is my code:
#include <iostream>
#include <string>
#include <iomanip>
#include <cstdlib>
using namespace std;
void readTextFile( int &Count, string playList[50][5]);
void userAddition( int &Count, string playList[50][5]);
int main()
{
string decision;
string playList[50][5];
int Count = 0;
readTextFile(Count, playList);
cout << "If you would like to add to the list, Please enter 'Y'. If you would like to exit
please enter 'N'. ----> ";
getline(cin, decision);
if (decision=="y" || decision=="Y")
userAddition(Count, playList);
else
{
return(0);
}
return 0;
} // End of Main FN.
void readTextFile( int &Count, string playList[50][5])
{
string inputfield;
ifstream infile("c:\\cTunes.txt", ifstream::in);
if ( infile.is_open() )
{
// File is read.
} // end if
else
{
cout << "Error Opening file" << endl;
return; //Program Closes.
} // end else
cout << setw(30)<<left<< "TITLE"<< setw(10) <<left<<"LENGTH"<<
// Outputs a title to each column that is displayed.
setw(40)<< left<<"ARTIST"<< setw(40) << left<<"ALBUM"<<
setw(15) << left <<"GENRE" << setw(5) << left << "RATING" << endl;
getline(infile, inputfield, '\t'); // read until tab
while(! infile.eof()) // loop until file is no longer valid.
{
playList[Count][0] = inputfield;
getline(infile, inputfield, '\t'); // read until tab.
playList[Count][1] = inputfield;
getline(infile, inputfield, '\t'); // read until tab.
playList[Count][2] = inputfield;
getline(infile, inputfield, '\t'); // read until tab.
playList[Count][3] = inputfield;
getline(infile, inputfield, '\t'); // read until tab.
playList[Count][4] = inputfield;
getline(infile, inputfield); // read until end of line.
playList[Count][5] = inputfield;
cout << setw(30)<<left<< playList[Count][0] << setw(10) <<left<<playList[Count][1] <<
// Output the line number equal to count.
setw(40)<< left<<playList[Count][2] << setw(40) << left<< playList[Count][3] <<
setw(15) << left << playList[Count][4] << setw(5) << left << playList[Count][5] <<
endl;
/*cout <<"Title: " << setw(25)<<left<< playList[Count][0]<<endl;
cout <<"Length: " << setw(5) <<left<<playList[Count][1] << endl;
cout <<"Artist: " << setw(50)<< left<<playList[Count][2] << endl;
cout <<"Album: " << setw(40) << left<< playList[Count][3] << endl;
cout <<"Genre: " << setw(15) << left << playList[Count][4] << endl;
cout <<"Rating: " << setw(5) << left << playList[Count][5] << endl<<endl;*/
Count++; // Increment counter by 1
getline(infile, inputfield, '\t'); // read next line until tab.
} // end while
infile.close(); // close the file being read from.
cout<<endl<<endl<<playList[0][5]<<endl;
} // End of readTextFile
I believe getline is causing the problem when reading till the end of the line but I'm truly at a loss.

First, note that in the following line:
cout << playList << endl;
you are printing the address of the array, not the contents. you will need
a loop to print the contents.
Second, in the following code:
if ( infile.is_open() )
{
// ok, read in the file
} // end if
else
{
cout << "Error Opening file" << endl;
//a return statement is missing
}
you need a return statement to avoid reading from a closed stream (which can cause a crash)
Finally, your function does not return anything, so it should either be declared void
or return some value (in which there is no sense according to the context).
Hope that helps and good luck!

The readTextFile function does not return anything. You need to return a string. If you are getting the error what(): basic_string::_S_construct null not valid then this is your problem. You can avoid similar problems by using -Wall compiler option.

You are using std::string for storing the string, std::ifstream for reading from a file, std::getline for reading words... you should really use std::vectors instead of arrays:
typedef std::vector<std::string> Line;
std::vector<Line> playList;
It will make things easier for you.
I also recommend you to change the way you read from a file to:
while(getline(...))
{
...
}
But since you are not allowed to use std::vector, your function could look like this:
// reads the content of input file and stores it into playList:
void readTextFile(std::ifstream& infile, std::string playList[][5])
{
std::string line;
for (int lineIndex = 0; getline(infile, line); ++lineIndex)
{
// skip empty lines:
if (line.empty()) continue;
std::string word;
std::istringstream lineStream(line);
for (int wordIndex = 0; getline(lineStream, word, '\t'); ++wordIndex)
{
// skip empty words:
if (line.empty()) continue;
playList[lineIndex][wordIndex] = word;
}
}
}
that could be used like this:
std::string playList[19][5];
std::ifstream infile("c:\\Test.txt");
if (infile.is_open())
{
readTextFile(infile, playList);
infile.close();
}
else
std::cout << "Error Opening file" << std::endl;
Also note that cout << playList << endl; outputs the address of the first word. To print all words, you will have to write a loop.

Related

How Do I read and Output the Contents of a File and the Number of Words it Contains?

I am attempting to write a program for homework which reads the contents of a notepad file and displays the contents and the number of words int he file. My code currently outputs nothing when I enter the name of the names of files I am using to test the program, and the input validation while loop I inserted does not function either.
#include <iostream>
#include <fstream>
using namespace std;
int main()
{
//Declare needed variables
string fileName, contents;
int wordCount = 0;
ifstream inData;
//Display program info
cout << "*** A SIMPLE FILE PROCESSING PROGRAM ***" << endl;
//Prompt user input
cout << "Enter a filename or type quit to exit: ";
cin >> fileName;
inData.open(fileName.c_str());
//Inform the user when their input is invalid and ask them to input another
file name
while (!inData)
{
inData.clear();
inData.ignore(200, '\n');
cout << "File not found. Please type a correct file name." << endl;
cin >> fileName;
inData.open(fileName.c_str());
}
inData >> contents;
//Read and output the contents of the selected file
while (inData)
{
cout << fileName << " data\n";
cout << "***********************" << endl;
inData >> contents;
wordCount++;
cout << contents << endl;
inData >> contents;
}
//Display the number of words in the file
cout << "***********************" << endl;
cout << fileName << " has " << wordCount << " words." << endl;
inData.close();
return 0;
}
The code compiles in its current state [but does not produce the desired outcome.
I will show you one of the many possible solutions.
But I would not recomend, to check the validity of a filename in a loop. You will give the user no chance to escape. Hence, I propose to open the file, and, if that does not work, show an error message and quit.
Then, what sounds easy in the beginning like, count the words, is not really that easy. What is a word? Characters only, or characters mixed with digits or even an underscore in it like for C++ variable names? Needs to be defined.
Additionally you may have separators like commas or one and more other white spaces. So a line like "Hello,,,,World" cannot be so easily counted. If you try to read the 2 words, then you will see a surprise.
std::string s1{};
std::string s2{};
std::istringstream iss("Hello,,,,World");
iss >> s1 >> s2;
Will read everything in s1!
The solution is that we define clearly what a word is. And this we will do with a std::regex. In the below example we use characters, digits and _
Then we use the regex_iterator to find all occurences of the regex (the word) in the line. We substract the end from the beginning with std::distance, which will give us the count of the words.
Then we give an output to the user in whatever format.
It may seem complicated. But it is precise. And rather flexible. Try to anaylze line by line and you will understand it.
Please see:
#include <iostream>
#include <string>
#include <regex>
#include <fstream>
#include <iomanip>
int main()
{
// Get a filename from the user
std::cout << "Enter a filename:\n";
std::string filename{}; std::cin >> filename;
// Try to open and read the file
std::ifstream fileStream(filename);
if (fileStream) {
// We will count all words
size_t numberOfWordsOverall{ 0 };
// We will also count the lines in the file
size_t lineCounter{ 1 };
// Define, what a word is. In this case: Characters, Digits and _
std::regex regexForWord("[\\w\\d_]+");
// Read all lines in file
std::string line{};
while (std::getline(fileStream, line)) {
// Count the numbers of words in one line
const size_t numberOfWordsInLine = std::distance(
std::sregex_token_iterator(line.begin(), line.end(), regexForWord, 1),
std::sregex_token_iterator()
);
// Update the overall word counter
numberOfWordsOverall += numberOfWordsInLine;
// Show result to user
std::cout << "# " << std::left << std::setw(2) << lineCounter++ << " (Words in line: "<< std::setw(2) << numberOfWordsInLine <<
" Words overall: " << std::setw(4) << numberOfWordsOverall << ") Line content --> " << line << '\n';
}
}
else {
std::cerr << "Could not open file '" << filename << "'\n";
}
return 0;
}
Hope this helps . . .

I'm working on reading and writing to files with c++

Hi guys I'm working on my last assignment of the computer science class. I think I'm doing everything fine but something is wrong. Can you take a look at it and tell what I'm doing wronger here.
here is what I get when I try to submit online on zybooks site:
"Your program produced no output"
Expected:
Ryan Hermle
22.99
Lochness Monster
3.50
Wonder Woman
123456.78
here are instructions from professor:
Constructor:
Takes a string parameter and stores that as fileName. Does not need to do anything else.
append:
Takes a record as a parameter that contains a string and a double
Open an output file stream in append mode using fileName
set its precision to 2 and fixed
Output the name, newline, the money, newline
searchName:
Open an input file stream with fileName
Loop while a getline and a double extraction are successful
if the string parameter is equal to the name read from the getline, then return the double
If the loop finishes without finding anything, return -1 to indicate that name was not found.
getData:
Open an input file stream with fileName
Construct an ostringstream
Set its precision to 2 and fixed
Loop while a getline and a double extraction are successful
ignore the \n left by the >> extraction
write the string, newline, double, newline to the ostringstream
return the string contained by the ostringstream
here is my main:
#include "Database.h"
int main()
{
Database db("data.txt");
db.append(Record{"Ryan Hermle", 22.99});
db.append(Record{"Lochness Monster", 3.50});
db.append(Record{"Wonder Woman", 123456.78});
}
and here is my Database.cpp file:
#include "Database.h"
Database::Database(string file)
{
fileName = file;
}
void Database::append(Record data)
{
ofstream out;
out.open(fileName, ios::app);
out << setprecision(2) << fixed;
cout << data.name << endl;
cout << data.money << endl;
out.close();
}
double Database::searchName(string n)
{
Record s;
ifstream in;
in.open(fileName);
while (getline(in, n) >> s.money)
{
in.ignore();
if (n == s.name)
{
return s.money;
}
}
return -1;
}
string Database::getData()
{
Record s;
ifstream ifs;
ifs.open(fileName);
ostringstream oss;
oss << setprecision(2) << fixed;
while(getline(ifs, s.name) >> s.money)
{
ifs.ignore();
oss << s.name << endl << s.money << endl;
cout << oss.str();
}
return oss.str();
}
Thanks for everyone who replied to my post. I was able figure out the error in my program.
The error was in append Function:
cout << data.name << endl;
cout << data.money << endl;
It should be like this:
out << data.name << endl;
out << data.money << endl;

C++ Searching CSV file from inputted string

I am trying to create a program that will load the CSV file and based upon the inputted word search through the file and return any lines that contain the word. The CSV file is a mass download of tweets and has the following columns:
Date & Time Created
The Tweet
The tweets are also surrounded by b'TWEET TEXT HERE' so would need to remove the b' ' from when it printed out. I am unable to change anything to do with the CSV file sadly so cant manually remove it. The issues I am having are:
Listing the total amount of tweets within the file the program just freezes
Removing the b' ' from the tweets
The else statement causes "not found" to be constantly printed
Code I currently have that is returning the tweets that contain the inputted word but also the false positive.
The current output when running the below code
#include "stdafx.h"
#include <cstring>
#include <fstream>
#include <iostream>
#include <string>
using namespace std;
int main()
{
string token;
ifstream fin;
fin.open("sampleTweets.csv");
if (fin.is_open())
{
cout << "File opened successfully" << "\n";
}
else {
cout << "Error opening file" << "\n";
}
cout << "Enter search word: ";
cin >> token;
"\n";
string line;
while (getline(fin, line)) {
if (line.find(token) != string::npos) {
cout << line << endl;
} else {
cout << token << " not found" << endl;
}
}
fin.close();
char anykey;
cout << "press any key";
cin >> anykey;
return 0;
}
Code I was using for counting total tweets
int count = 0;
char str[140];
while (!fin.eof())
{
fin.getline(str, 140);
count++;
}
cout << "Number of lines in file are " << count;
Any help on this would be amazing as I am quite new to C++ and not sure where to go from here!
You can remove the "b" with erase:
if (line.find(token) != string::npos){
int n= line.find(",");
line.erase(n+1, 3);
cout << line << endl;
}
and you can count the lines inside the while loop:
int count = 0;
while (getline(fin, line)) {
++count;
...
}
EDIT: you can remove the extra quotes and commas like so:
line[n] = ' '; // change comma int space
line.erase(n+1, 4); // remove "b""
line.resize(line.size()-5); // remove trailing """,,

Why can't I write to a file if it is located within an if statement?

I am trying to create a very simple program that writes to a file, but can't understand why it won't let me write to a file if I put it within an if statement! Here's the code:
#include "stdafx.h"
#include <iostream>
#include <fstream>
#include <string>
#include <stdlib.h>
using namespace std;
void readFile();
int main()
{
string line;
string today;
string readOrWrite;
cout << "Do you want to write to a file or read a file? " << endl;
cout << "Type \"write\" or \"read\" ";
cin >> readOrWrite;
if (readOrWrite == "read")
{
readFile();
}
else if (readOrWrite == "write")
{
cout << "How are you today? " << endl;
getline(cin, today);
ofstream myJournal;
myJournal.open("Journal.txt", ios::app);
myJournal << today << " ";
myJournal.close();
}
else
{
return 0;
}
return 0;
}
void readFile()
{
ifstream myJournal;
myJournal.open("Journal.txt");
string line;
if (myJournal.is_open())
{
while (getline(myJournal, line))
{
cout << line << endl;
}
myJournal.close();
}
else
{
cerr << "Error opening file ";
exit(1);
}
}
When I move it out of the if statement, it works smoothly and is able to write to the file, but when I place it inside, it opens the program, asks me the "Do you want to write to a file or read a file? ", I type "write", then it says "How are you today? " and then ends the program, printing "Press any key to continue...". Any help?
it says "How are you today? " and then ends the program, printing "Press any key to continue...". Any help?
std::istream::ignore should help in that case you are encountering.
cout << "How are you today? " << endl;
cin.ignore(10, '\n'); // Inserted
getline(cin, today);
Why do we need that in between?
It takes out 10 characters, which is enough amount of length, from the buffer and stops if it encounters a newline, which is '\n'. (Remember that you press the key 'enter' after typing "wrtie")
By doing so you can move on to the next new line, preventing std::cin from any parse failure.
More info : http://www.cplusplus.com/reference/istream/istream/ignore/

Example for file input to structure members?

I have the following structure:
struct productInfo
{
int item;
string details;
double cost;
};
I have a file that will input 10 different products that each contain an item, details, and cost. I have tried to input it using inFile.getline but it just doesn't work. Can anyone give me an example of how to do this? I would appreciate it.
Edit
The file contains 10 lines that look like this:
570314,SanDisk Sansa Clip 8 GB MP3 Player Black,55.99
Can you provide an example please.
Edit
Sorry guys, I am new to C++ and I don't really understand the suggestions. This is what I have tried.
void readFile(ifstream & inFile, productInfo products[])
{
inFile.ignore(LINE_LEN,'\n'); // The first line is not needed
for (int index = 0; index < 10; index++)
{
inFile.getline(products[index].item,SIZE,DELIMETER);
inFile.getline(products[index].details,SIZE,DELIMETER);
inFile.getline(products[index].cost,SIZE,DELIMETER);
}
}
This is another approach that uses fstream to read the file and getline() to read each line on the file. The parsing of the line itself was left out on purpose since other posts have already done that.
After each line is read and parsed into a productInfo, the application stores it on a vector, so all products could be accessed in memory.
#include <iostream>
#include <fstream>
#include <vector>
#include <iterator>
#include <string>
using namespace std;
struct productInfo
{
int item;
string details;
double cost;
};
int main()
{
vector<productInfo> product_list;
ifstream InFile("list.txt");
if (!InFile)
{
cerr << "CouldnĀ“t open input file" << endl;
return -1;
}
string line;
while (getline(InFile, line))
{ // from here on, check the post: How to parse complex string with C++ ?
// https://stackoverflow.com/questions/2073054/how-to-parse-complex-string-with-c
// to know how to break the string using comma ',' as a token
cout << line << endl;
// productInfo new_product;
// new_product.item =
// new_product.details =
// new_product.cost =
// product_list.push_back(new_product);
}
// Loop the list printing each item
// for (int i = 0; i < product_list.size(); i++)
// cout << "Item #" << i << " number:" << product_list[i].item <<
// " details:" << product_list[i].details <<
// " cost:" << product_list[i].cost << endl;
}
EDIT: I decided to take a shot at parsing the line and wrote the code below. Some C++ folks might not like the strtok() method of handling things but there it is.
string line;
while (getline(InFile, line))
{
if (line.empty())
break;
//cout << "***** Parsing: " << line << " *****" << endl;
productInfo new_product;
// My favorite parsing method: strtok()
char *tmp = strtok(const_cast<char*>(line.c_str()), ",");
stringstream ss_item(tmp);
ss_item >> new_product.item;
//cout << "item: " << tmp << endl;
//cout << "item: " << new_product.item << endl;
tmp = strtok(NULL, ",");
new_product.details += tmp;
//cout << "details: " << tmp << endl;
//cout << "details: " << new_product.details << endl;
tmp = strtok(NULL, " ");
stringstream ss_cost(tmp);
ss_cost >> new_product.cost;
//cout << "cost: " << tmp << endl;
//cout << "cost: " << new_product.cost << endl;
product_list.push_back(new_product);
}
It depends on what's in the file? If it's text, you can use the redirect operator on a file input stream:
int i;
infile >> i;
If it's binary, you can just read it in to &your_struct.
You have to
0) Create a new instance of productInfo, pinfo;
1) read text (using getline) to the first comma (','), convert this string to an int, and put it into pinfo.item.
2) read text to the next comma and put it into pinfo.details;
3) read text to the endline, convert the string to a double, and put it into pinfo.cost.
Then just keep doing this until you reach the end of the file.
Here is how I would use getline. Note that I use it once to read from the input file, and then again to chop that line at ",".
ostream& operator>>(istream& is, productInfo& pi)
{
string line;
getline(is, line); // fetch one line of input
stringstream sline(line);
string item;
getline(sline, item, ',');
stringstream(item) >> pi.item; // convert string to int
getline(sline, item, ',');
pi.details = item; // string: no conversion necessary
getline(sline, item);
stringstream(item) >> pi.cost; // convert string to double
return is;
}
// usage:
// productInfo pi; ifstream inFile ("inputfile.txt"); inFile >> pi;
N.b.: This program is buggy if the input is
99999,"The Best Knife, Ever!",16.95