csci-e215 Final Exam


                        May 16, 1994, USA





              Your Name Here: ____________________





          Instructions:   You  have  two hours for this
          exam.  This exam  is  `open  notes  and  open
          book'.   Please  write  your  answers  on the
          pages in this exam booklet.  No  scrap  paper
          or additional sheets will be accepted.  Watch
          your  time,  be  concise,  think  before  you
          write, look before you  leap,  listen  before
          you accept, and always check the return value
          of a system call.  Good luck.




































               +------+--------+-----+---------+
               | prob | points | got | section |
               +------+--------+-----+---------+
               |   1  |   5    |     |         |
               +------+--------+-----+---------+
               |   2  |   5    |     |         |
               +------+--------+-----+---------+
               |   3  |   5    |     |         |
               +------+--------+-----+---------+
               |   4  |   5    |     |         |
               +------+--------+-----+---------+
               |   5  |   5    |     |         |
               +------+--------+-----+---------+
               |   6  |   5    |     |         |
               +------+--------+-----+---------+
               |   7  |   5    |     |         |
               +------+--------+-----+---------+
               |      |        |     |         |
               +------+--------+-----+---------+
               |   8  |   6    |     |         |
               +------+--------+-----+---------+
               |   9  |   6    |     |         |
               +------+--------+-----+---------+
               |  10  |   6    |     |         |
               +------+--------+-----+---------+
               |  11  |   6    |     |         |
               +------+--------+-----+---------+
               |  12  |   6    |     |         |
               +------+--------+-----+---------+
               |  13  |   6    |     |         |
               +------+--------+-----+---------+
               |  14  |   6    |     |         |
               +------+--------+-----+---------+
               |      |        |     |         |
               +------+--------+-----+---------+
               |  a   |   5    |     |         |
               +------+--------+-----+---------+
               |  b   |   5    |     |         |
               +------+--------+-----+---------+
               |  c   |   5    |     |         |
               +------+--------+-----+---------+
               |  d   |   5    |     |         |
               +------+--------+-----+---------+
               |  e   |   3    |     |         |
               +------+--------+-----+---------+
               |      |        |     |         |
               +------+--------+-----+---------+
               |      |        |     |         |
               +------+--------+-----+---------+
















Part One       Seven Problems, each worth 5 points         page 1
_________________________________________________________________

Problems  1-7:   Each  problem  describes a particular task.  For
each one, state which system call(s) you  would  use  to  perform
that  task.   In  the third column, state clearly and briefly the
logic of your solution.





























































































































Part Two       Seven problems, each worth 6 points         page 2
_________________________________________________________________

Problems 8-14: Compare and contrast.  Each of these problems men-
tions two related concepts, system  calls,  or  operations.   For
each pair, explain briefly and clearly (a) what they have in com-
mon,  (b)  when  you  would  use the first item, and (c) when you
would use the second item.


8. pipe() , socket()
















9. open(), fopen()
















10. stat(), ioctl()





















Part Two                    continued                      page 3
_________________________________________________________________

11. rawmode, cbreak mode












12. sleep(), wait()












13. datagram socket, stream socket












14. errno, perror()























Part Three            One problem, 23 points               page 4
_________________________________________________________________
15. Another Unix utility: du

The Unix utility called du is described in the manual as:


   Name
     du - print amount of disk usage

   Syntax
     du [-as] [name...]

   Description
     The du command gives the number of kilobytes contained in all files and,
     recursively, directories within each specified directory or file name.
     If name is missing, `.' is used.

     Absence of either -a or -s causes an entry to be generated for each
     directory only.

     A file that has two links to it is only counted once.

   Options

     -a   Displays the disk usage for each file.

     -s   Displays a summary total only.

   Bugs
     Non-directories given as arguments (not under -a option) are not listed.

     If there are too many distinct linked files, du counts the excess files
     multiply.

    For this part of the exam,  answer  the  following  questions
about  the  design  and  components of du.   Use the space on the
remaining pages.

   a) What system calls will you need to use  in  writing  du?
   What role will each play in the program? [5]

   b)  Write  a  pseudo-code (or top-level function in C) that
   outlines the major operation of your program. [5]

   c) Do directories consume disk space?  Why or why not?  How
   does your program address this topic? [5]

   d) How will you handle the requirement that multiple  links
   are  counted  once?   Be quite specific, and discuss how to
   handle errors. [5]

   e) Fill in the details of the code to any  degree  of  com-
   pleteness you like.  [3]












Part Three                  continued                      page 5
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Part Three                  continued                      page 6
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