Reference
C Library
IOstream Library
Strings library
STL Containers
STL Algorithms
Miscellaneous
C Library
cassert (assert.h)
cctype (ctype.h)
cerrno (errno.h)
cfloat (float.h)
ciso646 (iso646.h)
climits (limits.h)
clocale (locale.h)
cmath (math.h)
csetjmp (setjmp.h)
csignal (signal.h)
cstdarg (stdarg.h)
cstddef (stddef.h)
cstdio (stdio.h)
cstdlib (stdlib.h)
cstring (string.h)
ctime (time.h)
cstdio (stdio.h)
functions:
clearerr
fclose
feof
ferror
fflush
fgetc
fgetpos
fgets
fopen
fprintf
fputc
fputs
fread
freopen
fscanf
fseek
fsetpos
ftell
fwrite
getc
getchar
gets
perror
printf
putc
putchar
puts
remove
rename
rewind
scanf
setbuf
setvbuf
sprintf
sscanf
tmpfile
tmpnam
ungetc
vfprintf
vprintf
vsprintf
macro constants:
EOF
FILENAME_MAX
NULL
TMP_MAX
objects:
stderr
stdin
stdout
types:
FILE
fpos_t
size_t


fwrite

function
<cstdio>
size_t fwrite ( const void * ptr, size_t size, size_t count, FILE * stream );

Write block of data to stream

Writes an array of count elements, each one with a size of size bytes, from the block of memory pointed by ptr to the current position in the stream.
The postion indicator of the stream is advanced by the total number of bytes written.
The total amount of bytes written is (size * count).

Parameters

ptr
Pointer to the array of elements to be written.
size
Size in bytes of each element to be written.
count
Number of elements, each one with a size of size bytes.
stream
Pointer to a FILE object that specifies an output stream.

Return Value

The total number of elements successfully written is returned as a size_t object, which is an integral data type.
If this number differs from the count parameter, it indicates an error.

Example

1
2
3
4
5
6
7
8
9
10
11
12
/* fwrite example : write buffer */
#include <stdio.h>
int main ()
{
  FILE * pFile;
  char buffer[] = { 'x' , 'y' , 'z' };
  pFile = fopen ( "myfile.bin" , "wb" );
  fwrite (buffer , 1 , sizeof(buffer) , pFile );
  fclose (pFile);
  return 0;
}


A file called myfile.bin is created and the content of the buffer is stored into it. For simplicity, the buffer contains char elements but it can contain any other type.
sizeof(buffer) is the length of the array in bytes (in this case it is three, because the array has three elements of one byte each).

See also