Prev Next

Writing to Files in C

Writing data to files allows you to store output generated by your program. C provides several functions for writing to files.

1. Functions to Write to Files

Function Description
fprintf(FILE *fp, const char *format, ...)Writes formatted output to a file.
fputs(const char *str, FILE *fp)Writes a string to a file.
fputc(int char, FILE *fp)Writes a character to a file.
fwrite(const void *ptr, size_t size, size_t nmemb, FILE *fp)Writes data from an array to a file.

2. Example: Writing Text to a File

#include <stdio.h>
#include <stdlib.h>

int main() {
    FILE *fptr;
    fptr = fopen("output.txt", "w");
    if (fptr == NULL) {
        printf("Error opening file!\n");
        exit(1);
    }
    fprintf(fptr, "This is a line of text.\n");
    fputs("This is another line.\n", fptr);
    fclose(fptr);
    printf("Data written to file successfully.\n");
    return 0;
}

3. Example: Writing Binary Data to a File

#include <stdio.h>
#include <stdlib.h>

int main() {
    FILE *fptr;
    int numbers[] = {1, 2, 3, 4, 5};
    fptr = fopen("data.bin", "wb");
    if (fptr == NULL) {
        printf("Error opening file!\n");
        exit(1);
    }
    fwrite(numbers, sizeof(int), 5, fptr);
    fclose(fptr);
    printf("Binary data written to file successfully.\n");
    return 0;
}

Best Practices

  • Use fprintf() for formatted text output.
  • Ensure the file is opened in the correct mode (e.g., "w" for writing).
  • Check the return value of writing functions for errors.

Don'ts

  • Don't forget to flush buffers if necessary using fflush().
  • Don't assume data is written immediately; buffering may delay writing.
  • Don't neglect to close the file after writing.

Key Takeaways

  • Writing to files is essential for data persistence.
  • Different functions are available for writing text and binary data.
  • Proper error handling ensures data integrity.
Prev Next