Introduction

File handling in C allows programmers to store data permanently in files and retrieve it whenever needed. C provides various functions to create, read, write, and modify files.

Key Functions for File Handling

• fopen(): Opens a file.
• fprintf(): Writes formatted data to a file.
• fscanf(): Reads formatted data from a file.
• fclose(): Closes a file.
• fgets(): Reads a line from a file.
• fputs(): Writes a line to a file.
• fseek(): Moves the file pointer to a specific location.
• fflush(): Flushes the output buffer, forcing data to be written immediately.

Using fflush()

The fflush() function is used to clear the output buffer by writing its content to the file immediately. It is often used when writing to files to ensure data is saved, especially in programs with intermediate outputs.

Example: Writing to a File with fflush()

#include <stdio.h>

int main() {
    FILE *filePointer = fopen("data.txt", "w");
    if (filePointer == NULL) {
        printf("Error: Could not open file.\n");
        return 1;
    }

    fprintf(filePointer, "This is a test line.\n");
    fflush(filePointer); // Force writing data to the file immediately

    fprintf(filePointer, "Another line written after flushing.\n");
    fclose(filePointer);

    printf("Data written and flushed successfully.\n");
    return 0;
}
      

Output: The file data.txt will immediately contain the first line, even before the second line is written.

Additional Notes:

• fflush(stdout): Clears the output buffer of the console (used for printf).
• Always close the file with fclose() after flushing.
• fflush(stdin) is non-standard and may behave unpredictably on some compilers.

Unsolved Problems