fwrite-优快云博客

本文链接：https://blog.youkuaiyun.com/dadalan/article/details/4327991

本文详细介绍了fwrite函数的功能，该函数用于将指定数量的数据块从内存写入到文件流中，并更新流的位置指示器。通过示例代码展示了如何使用此函数来创建并写入二进制文件。当fwrite成功执行时，它会返回实际写入的数据元素数量。

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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

/* 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).