×

Search anything:

fscanf not reading next line [FIXED]

C++

Internship at OpenGenus

Get this book -> Problems on Array: For Interviews and Competitive Programming

In this article, we have explored why a C++ code using fscanf cannot read next line and how to fix it by using getline() and sscanf() in C++ by keeping the syntax same. We have demonstrated this with C++ code examples.

Table of contents:

  1. Understanding the problem and fix
  2. fscanf not reading next line
  3. Fix with C++ code

Understanding the problem and fix

This is the major problem with using fscanf to read data from a text file. The issue is fscanf does not recognize new line character (\0).

The fix is to:

  • Read each line one by one using getline()
  • Extract data from each line using sscanf() just like fscanf() (same syntax)

fscanf not reading next line

Let the file (opengenus.txt) be of the following format:

10, 53, 101
-9, 33, 10
44, 2, 1
1, 2, 3
5, 0, 5
...
#include <string.h>
#include <cstdlib>

int main(int argc, char** argv) {
    FILE* my_file = fopen("opengenus.txt", "r");
    int data[100][3];

    for(int count = 0; count < 100; count++) {
        int got = fscanf(my_file, "%d,%d,%d", data[count][0], 
                  data[count][2], data[count][2]);
    }
}

The issue with the above C++ code is that fscanf cannot read the next line and reads only the first line of the file.

Fix with C++ code

Following is the correct C++ code:

#include <string.h>
#include <cstdlib>

int main(int argc, char** argv) {
    FILE* my_file = fopen("opengenus.txt", "r");
    char* line = NULL;
    size_t len = 0;
    int data[100][3];

    for(int count = 0; count < 100; count++) {
        size_t read = getline(&line, &len, my_file);

        int got = sscanf(line, "%d,%d,%d", data[count][0], 
                  data[count][2], data[count][2]);
    }
}

With this article at OpenGenus, you must have the complete idea of how to fix the problem of fscanf not reading next line.

Aditya Chatterjee

Aditya Chatterjee

Aditya Chatterjee is an Independent Algorithmic Researcher, Software Developer and Technical Author. He is the founding member of OPENGENUS, an organization with focus on changing Internet consumption

Read More

Improved & Reviewed by:


OpenGenus Foundation OpenGenus Foundation
fscanf not reading next line [FIXED]
Share this