#include <io.h> 
#include <fcntl.h> 
#include <sys\stat.h> 
#include <process.h> 
#include <share.h> 
#include <stdio.h> 

int main(void) 
{ 
   int handle, status; 
   long length; 

   /* Must have DOS Share.exe loaded for */ 
   /* file locking to function properly */ 

   handle = sopen("c:\\autoexec.bat", 
      O_RDONLY,SH_DENYNO,S_IREAD); 

   if (handle < 0) 
   { 
      printf("sopen failed\n"); 
      exit(1); 
   } 

   length = filelength(handle); 
   status = lock(handle,0L,length/2); 

   if (status == 0) 
      printf("lock succeeded\n"); 
   else 
      printf("lock failed\n"); 

   status = unlock(handle,0L,length/2); 

   if (status == 0) 
      printf("unlock succeeded\n"); 
   else 
      printf("unlock failed\n"); 

   close(handle); 
   return 0; 
}