fwrite

Input-Output Functions

Write unformatted data from a buffer to a stream. 

size_t fwrite( const void *buffer, size_t size, size_t count, FILE *file_pointer);

buffer The buffer containing the data.
size The size of the buffer.
count The number of bytes to store in the buffer.
file_pointer A pointer to a file that will store the data.

Return Values

If successful, the function returns the number of full items (not bytes) successfully written.

Example

The following example gives values to a student record, sd, and then writes it to a file using fwrite.

Copy code
    #include <stdio.h>
    #ifdef unix
        char * filename = "/tmp/marks.txt";
    #else
        char * filename = "c:\\marks.txt";
    #endif
    struct student_data {
        int student_id;
        unsigned char marks[10];
    };
    FILE* file;
    struct student_data sd;
    int i;
    if ((file = fopen(filename, "w+")) == NULL) {
        lr_output_message ("Unable to create %s", filename);
        return -1;
    }
    sd.student_id = 1001;
// Set the marks of student 1001
    for (i = 0; i < 10; i++)
         sd.marks[i] = (unsigned char)(85 + i);
// Write student record to the file
        i = fwrite(&sd, sizeof(struct student_data), 1, file);
    if (i > 0)
        lr_output_message ("Successfully wrote %d record", i);
    fclose(file);
Example: Output:
Successfully wrote 1 record