fprintf() in C

fprintf() is a standard library function used to write formatted output to a specified file or output stream.

• It works like printf(), but writes the output to a file instead of the console.
• It supports format specifiers such as %d, %f, %c, and %s for formatted file output.

#include <stdio.h>

int main() {
    FILE *fp = fopen("data.txt", "w");

    if (fp == NULL) {
        printf("Error opening file.\n");
        return 1;
    }

    int id = 101;
    float salary = 45000.50;
    char name[] = "Rahul";

    fprintf(fp, "ID: %d\n", id);
    fprintf(fp, "Name: %s\n", name);
    fprintf(fp, "Salary: %.2f\n", salary);

    fclose(fp);

    printf("Data written successfully.\n");

    return 0;
}

Data written successfully.

Syntax

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

Parameters:

• stream: Pointer to the file where the output will be written.
• format: Format string containing text and format specifiers.
• ... : Additional values to be written to the file.

Return Value:

• Returns the number of characters written on success.
• Returns a negative value if an error occurs.

Advantages

fprintf() is widely used for writing formatted output to files in C programs.

• It writes formatted data directly to a file instead of displaying it on the console.
• It supports format specifiers such as %d, %f, %c, and %s for formatted output.
• It is useful for creating logs, reports, configuration files, and storing program output.

printf() Vs fprintf()