fwrite

write a number of elements into a file

Synopsis:

#include <stdio.h>
size_t fwrite( const void *buf,
               size_t elsize,
               size_t nelem,
               FILE *fp );

Description:

The fwrite() function writes nelem elements of elsize bytes each to the file specified by fp.

Returns:

The fwrite() function returns the number of complete elements successfully written. This value will be less than the requested number of elements only if a write error occurs. When an error has occurred, errno contains a value that indicates the type of error that has been detected.

See also:

errno, ferror(), fopen()

Examples:

#include <stdio.h>

struct student_data {
    int  student_id;
    unsigned char marks[10];
};

void main()
  {
    FILE *fp;
    struct student_data std;
    int i;

    fp = fopen( "file", "w" );
    if( fp != NULL ) {
      std.student_id = 1001;
      for( i = 0; i < 10; i++ )
        std.marks[ i ] = (unsigned char) (85 + i);

      /* write student record with marks */
      i = fwrite( &std, sizeof(std), 1, fp );
      printf( "%d record written\n", i );
      fclose( fp );
    }
  }

Classification:

ANSI

Systems:

All (except DOS/PM)