4.31 fwrite—write array elements

Synopsis

     #include <stdio.h>
     size_t fwrite(const void *buf, size_t size,
         size_t count, FILE *fp);
     
     #include <stdio.h>
     size_t _fwrite_r(struct _reent *ptr, const void *buf, size_t size,
         size_t count, FILE *fp);
     

Description
fwrite attempts to copy, starting from the memory location buf, count elements (each of size size) into the file or stream identified by fp. fwrite may copy fewer elements than count if an error intervenes.

fwrite also advances the file position indicator (if any) for fp by the number of characters actually written.

_fwrite_r is simply the reentrant version of fwrite that takes an additional reentrant structure argument: ptr.

Returns
If fwrite succeeds in writing all the elements you specify, the result is the same as the argument count. In any event, the result is the number of complete elements that fwrite copied to the file.

Portability
ANSI C requires fwrite.

Supporting OS subroutines required: close, fstat, isatty, lseek, read, sbrk, write.