CODEWITHSUNDEEP
c++fileinputgetline
Alex
Alex

Reputation: 125

How to read and process text from a file in this specific way?

I have a question regarding some code to process some names or numbers from a file I'm reading. So the text in the file looks like this:

Imp;1;down;67
Comp;3;up;4
Imp;42;right;87

As you can see , there are 3 lines with words and numbers delimited by the character ';' . I want to read each line at a time, and split the entire string in one line into the words and numbers , and then process the information (will be used to create a new object with the data). Then move on to the next line, and so on, until EOF.

So, i want to read the first line of text, split it into an array of strings formed out of the words and numbers in the line , then create an object of a class out of them. For example for the first line , create an object of the class Imp like this Imp objImp(Imp, 1, down, 67) .

In Java i did the same thing using information = line.split(";")' (where line was a line of text) and then used information[0], information[1] to access the members of the string array and create the object. I`m trying to do the same here

Upvotes: 0

Views: 1003

Answers (2)

paulsm4
paulsm4

Reputation: 121881

One other (slightly different) alternative:

/*
 * Sample output:
 *   line:Imp;1;down;67
 *     "Imp", "1", "down", "67"
 *   line:Comp;3;up;4
 *     "Comp", "3", "up", "4"
 *   line:Imp;42;right;87
 *     "Imp", "42", "right", "87"
 *   line:Imp;42;right;87
 *     "Imp", "42", "right", "87"
 */
#include <iostream>
#include <fstream>
#include <sstream>
#include <string>
#include <vector>

using namespace std;

void split(const std::string &s, char delim, std::vector<string> &fields)
{
    fields.clear();
    std::stringstream ss(s);
    std::string item;
    while (std::getline(ss, item, delim)) {
        fields.push_back(item);
    }
}

void print (std::vector<string> &fields)
{
  cout << "  ";
  for (size_t i = 0; i < fields.size() - 1; i++)
    cout << "\"" << fields[i] << "\", ";
  cout << "\"" << fields[fields.size()-1] << "\"" << endl;
}

int main ()
{
  std::ifstream fp("tmp.txt");
  std::string line;
  while (!fp.eof()) {
    fp >> line;
    cout << "line:" << line << endl;
    std::vector<std::string> fields;
    split(line, ';', fields);
    print(fields);
  }
  fp.close();
  return 0;
}

Upvotes: 1

LogicStuff
LogicStuff

Reputation: 19627

Don't use char array for buffer, and don't use std::istream::eof. That's been said, let's continue in solving the problem.

std::getline is simmilar to std::istream::getline, except that it uses std::string instead of char arrays.

In both, the parameter delim means a delimiting character, but in a way that it's the character, which when encountered, std::getline stops reading (does not save it and discards it). It does not mean a delimiter in a way that it will magically split the input for you between each ; on the whole line.

Thus, you'll have to do this:

#include <iostream>
#include <fstream>
#include <sstream>
#include <string>

...

std::ifstream myFile("D:\\stuff.txt"); // one statement

if (myFile.is_open()) {
    std::string line;

    while (std::getline(myFile, line)) { // line by line reading
        std::istringstream line_stream(line);
        std::string output;

        while (std::getline(line_stream, output, ';')) // line parsing
            std::cout << output << std::endl;
    }
}

We construct a std::istringstream from line, so we can parse it again with std::getline.

Upvotes: 3

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