How to Read Numeric Data from a Text File in C : What are the Different Approaches?

How to Read Numeric Data from a Text File in C

Reading numeric data from text files is a common task in C . It involves accessing a file and extracting numbers from it.

Approach 1: Using Multiple >> Operators

This approach involves chaining the >> operator to read multiple numbers from the file. For instance, the following code reads three numbers:

float a, b, c;
myfile >> a >> b >> c;

Approach 2: Using >> in a Loop

This method uses a loop to repeatedly read numbers from the file and store them in a variable. An example is:

while (myfile >> a)
{
    // Process the value
}

Example: Reading Numbers from a File

Consider the following text file named "data.txt":

45.78   67.90   87
34.89   346     0.98

The following C program reads the numbers from this file and prints them out:

#include <iostream>
#include <fstream>

int main()
{
    std::fstream myfile("data.txt", std::ios_base::in);

    float a;
    while (myfile >> a)
    {
        std::cout << a << " ";
    }

    myfile.close();

    return 0;
}

Output:

45.78 67.90 87.00 34.89 346.00 0.98

Alternative Approaches

• Storing Data in an Array: If you know the total number of numbers, you can store them in an array.
• Skipping Values: To skip a certain number of values, use a loop and discard those values.

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