_filelength - Determine File Length

Syntax

#include <io.h>
long _filelength(int handle);

filelength returns the length, in bytes, of the file associated with handle. The length of the file will be correct even if you have the handle opened and have appended data to the file.

A return value of -1L indicates an error, and errno is set to one of the following values: compact break=fit.

Value

Meaning

The file handle is incorrect or the mode specified does not match the mode you opened the file with.

The call to the operating system was not successful.

This example opens a file and tries to determine the current length of the file using _filelength.

#include <io.h>#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>

int main(void)
{
   long length;
   int fh;

   printf("\nCreating sample.dat.\n");
   system("echo Sample Program > sample.dat");
   if (-1 == (fh = open("sample.dat", O_RDWR|O_APPEND))) {
      printf("Unable to open sample.dat.\n");
      return EXIT_FAILURE;
   }
   if (-1 == (length = _filelength(fh))) {
      printf("Unable to determine length of sample.dat.\n");
      return EXIT_FAILURE;
   }
   printf("Current length of sample.dat is %d.\n", length);
   close(fh);
   return 0;

   /****************************************************************************
      The output should be:

      Creating sample.dat.
      Current length of sample.dat is 17.
   ****************************************************************************/
}

chsize
eof

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