Header File 

io.h  

Category 

Input/output Routines 

Prototype 

int chsize(int handle, long size); 

Description 

Changes the file size. 

chsize changes the size of the file associated with handle. It can truncate or extend the file, depending on the value of size compared to the file's original size. 

The mode in which you open the file must allow writing. 

If chsize extends the file, it will append null characters (\0). If it truncates the file, all data beyond the new end-of-file indicator is lost. 

Return Value 

On success, chsize returns 0. On failure, it returns -1 and the global variable errno is set to one of the following values:

Example

#include <string.h>
#include <fcntl.h>
#include <io.h>
int main(void)
{
   int handle;
   char buf[11] = "0123456789";
   /* create text file containing 10 bytes */
   handle = open("DUMMY.FIL", O_CREAT);
   write(handle, buf, strlen(buf));
   /* truncate the file to 5 bytes in size */
   chsize(handle, 5);
   /* close the file */
   close(handle);
   return 0;
}

Portability