函数名: chsize 
 功  能: 改变文件大小 
 用  法: #include <io.h> 
         int chsize(int handle, long size); 
 程序例: 
#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; 
 }