ftell

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http://www.cplusplus.com/reference/cstdio/ftell/ [点击打开链接][Link 1]

# 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 ###

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   <td style="background-color:rgb(239,239,255); border:1px solid rgb(192,192,208); vertical-align:top"> <pre style="margin-top:0px; margin-bottom:0px"><code><cite style="font-style:normal; color:rgb(0,112,0)">/* ftell example : getting size of a file */</cite>
#include &lt;stdio.h&gt;

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

pFile = fopen ("myfile.txt","rb");
  if (pFile==NULL) perror ("Error opening file");
  else
  {
    fseek (pFile, 0, SEEK_END);   <cite style="font-style:normal; color:rgb(0,112,0)">// non-portable</cite>
    size=ftell (pFile);
    fclose (pFile);
    printf ("Size of myfile.txt: %ld bytes.\n",size);
  }
  return 0;
}</code></pre> </td> 
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       <a href="http://www.cplusplus.com/reference/cstdio/ftell/#" title="Open C++ Shell (in a new window)" style="text-decoration:none; color:rgb(0,0,112)" rel="nofollow"><span style="display:inline-block; width:16px; height:16px; line-height:16px; vertical-align:middle; margin:0px; padding:0px"></span>Edit &amp; Run</a> 
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This program prints out the size of  myfile.txt in bytes (where supported).

[Link 1]: http://www.cplusplus.com/reference/cstdio/ftell/
[fseek]: http://www.cplusplus.com/fseek
[ungetc]: http://www.cplusplus.com/ungetc
[FILE]: http://www.cplusplus.com/FILE
[errno]: http://www.cplusplus.com/errno