fwrite

Writes data to a stream.

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

For additional compatibility information, see Compatibility in the Introduction.

Libraries

Return Value

fwrite returns the number of full items actually written, which may be less than count if an error occurs. Also, if an error occurs, the file-position indicator cannot be determined.

Parameters

buffer

Pointer to data to be written

size

Item size in bytes

count

Maximum number of items to be written

stream

Pointer to FILE structure

Remarks

The fwrite function writes up to count items, of size length each, from buffer to the output stream. The file pointer associated with stream (if there is one) is incremented by the number of bytes actually written. If stream is opened in text mode, each carriage return is replaced with a carriage-return – linefeed pair. The replacement has no effect on the return value.

Example

/* FREAD.C: This program opens a file named FREAD.OUT and
 * writes 25 characters to the file. It then tries to open
 * FREAD.OUT and read in 25 characters. If the attempt succeeds,
 * the program displays the number of actual items read.
 */

#include <stdio.h>

void main( void )
{
   FILE *stream;
   char list[30];
   int  i, numread, numwritten;

   /* Open file in text mode: */
   if( (stream = fopen( "fread.out", "w+t" )) != NULL )
   {
      for ( i = 0; i < 25; i++ )
         list[i] = (char)('z' - i);
      /* Write 25 characters to stream */
      numwritten = fwrite( list, sizeof( char ), 25, stream );
      printf( "Wrote %d items\n", numwritten );
      fclose( stream );

   }
   else
      printf( "Problem opening the file\n" );

   if( (stream = fopen( "fread.out", "r+t" )) != NULL )
   {
      /* Attempt to read in 25 characters */
      numread = fread( list, sizeof( char ), 25, stream );
      printf( "Number of items read = %d\n", numread );
      printf( "Contents of buffer = %.25s\n", list );
      fclose( stream );
   }
   else
      printf( "File could not be opened\n" );
}

Output

Wrote 25 items
Number of items read = 25
Contents of buffer = zyxwvutsrqponmlkjihgfedcb

Stream I/O Routines

See Also   fread, _write