ftell

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本文提供了一个简单的C++程序示例，演示如何使用ftell函数获取文件大小。程序通过打开指定文件，使用ftell函数获取当前位置，并最终打印文件大小。

http://www.cplusplus.com/reference/cstdio/ftell/ 点击打开链接

  <cstdio>

ftell

long int ftell ( FILE * stream );

Get current position in stream

Returns the current value of the position indicator of the stream.

For binary streams, this is the number of bytes from the beginning of the file.

For text streams, the numerical value may not be meaningful but can still be used to restore the position to the same position later using fseek (if there are characters put back using ungetc still pending of being read, the behavior is undefined).

Parameters

stream

Pointer to a FILE object that identifies the stream.

Return Value

On success, the current value of the position indicator is returned.
On failure, -1L is returned, and errno is set to a system-specific positive value.

Example

/* ftell example : getting size of a file */
#include <stdio.h>

int main ()
{
  FILE * pFile;
  long size;

  pFile = fopen ("myfile.txt","rb");
  if (pFile==NULL) perror ("Error opening file");
  else
  {
    fseek (pFile, 0, SEEK_END);   // non-portable
    size=ftell (pFile);
    fclose (pFile);
    printf ("Size of myfile.txt: %ld bytes.\n",size);
  }
  return 0;
}