Reading Data from a File Using fscanf in C programming

Reading Data from a File Using fscanf in C

The fscanf function in C is used to read formatted data from a file. It allows you to parse and retrieve data from a file using format specifiers, similar to how you use scanf to read from standard input.

Syntax

The syntax for fscanf is as follows:

int fscanf(FILE *stream, const char *format, ...);

Where:

• stream is a pointer to a FILE object that identifies the input stream (e.g., a file).
• format is the format string that specifies how the input data should be parsed.
• ... represents additional pointers to variables where the parsed data will be stored.

Example Code

#include <stdio.h>

int main() {
    FILE *file = fopen("data.txt", "r");
    int age;
    float height;

    if (file != NULL) {
        // Read an integer and a floating-point number from the file
        fscanf(file, "%d %f", &age, &height);
        
        fclose(file); // Close the file after reading

        // Output the read values
        printf("Age: %d\n", age);
        printf("Height: %.2f\n", height);
    } else {
        printf("Error opening file.\n");
    }

    return 0;
}

In this example:

• FILE *file = fopen("data.txt", "r"); opens the file data.txt for reading. Ensure the file exists in the working directory.
• fscanf(file, "%d %f", &age, &height); reads an integer and a floating-point number from the file and stores them in age and height variables, respectively.
• fclose(file); closes the file to free up resources after reading.
• printf("Age: %d\n", age); and printf("Height: %.2f\n", height); display the values read from the file.

Key Points

• File Handling: Always check if the file is successfully opened before using fscanf. Handle potential errors if the file cannot be opened.
• Format Specifiers: Use format specifiers in fscanf to match the type and format of data in the file (e.g., %d for integers, %f for floating-point numbers).
• Buffer Management: Ensure the buffer variables are correctly defined and match the format specifiers used in fscanf.

Note: Be cautious of the format and data types when using fscanf. Mismatched format specifiers or incorrect data types can lead to incorrect readings or runtime errors.