text: #include	"unpipc.h"
  
  #define	LOCKFILE	"/tmp/seqno.lock"
  #define	PREFIX		"/tmp"		/* prefix for temp pathname */
  
  void
  my_lock(int fd)
  {
  	char	*ptr;
  
  	ptr = tempnam(PREFIX, NULL);
  		/* create/open and then close */
  	Close(Open(ptr, O_CREAT | O_RDWR | O_TRUNC, FILE_MODE));
  
  	while (link(ptr, LOCKFILE) < 0) {
  		if (errno != EEXIST)
  			err_sys("link error for lock file");
  		/* someone else has the lock, loop around and try again */
  	}
  	Unlink(ptr);			/* linked the file, we have the lock */
  	free(ptr);				/* tempnam() calls malloc() */
  }
  
  void
  my_unlock(int fd)
  {
  	Unlink(LOCKFILE);		/* release lock by removing file */
  }
  