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CS 476/576
Systems Programming
Fall 2012
Midterm Exam

Time 2 & 1/2 hours
Open Book & Notes

 

 

 

Login:

 

Name:

Question 1:  20 points

 

What is the output of the following two shell scripts?

q1a.shell:

 

#! /bin/sh
echo 1 > file
tail -f file >> file &
while :
do
count=`wc -c < file`
if test $count -gt 1000
then
   echo $count
   pkill tail
   exit
fi
done


% q1a.shell file

 

 

q1b.shell:

#! /bin/sh
echo HI1 | tee /dev/tty > $1
echo HI2 | tee /dev/tty >> $1
echo HI3 | tee /dev/tty > $1
echo HI4 | tee /dev/tty >> $1
echo 'cat $1'
cat $1
echo "cat $1"
cat $1
echo '`cat $1`'
echo "`cat $1`"

 

% q1b.shell file

 

Question 2:  20 points

The following shell script q2.shell has the syntax:

 

q2.shell  <letter> u1 u2 ...

 

will email  <letter> to users u1, u2, ...

 

Modify the script to prepend a line at the top of the letter that says:

 

Dear <full_name>:

 

Example:

 

Assume invitationfile contains:

 

I would like to invite you for dinner

this weekend at my home.

Hussein

 

% q2.shell “Special Party Invitation” invitationfile  wahab  maly

 

 

user  wahab   will get :

 

Dear Hussein Abdel-Wahab:

I would like to invite you for dinner

this weekend at my home.

Hussein

 

since wahab’s UNIX entry is:

wahab:abc:51:13:Hussein Abdel-Wahab:/home/wahab:/usr/local/bin/tcsh

 

while user maly  will get:

 

Dear Kurt Maly:

I would like to invite you for dinner

this weekend at my home.

Hussein

 

Since maly’s UNIX entry is:

maly:xyz:79:13:Kurt Maly:/home/maly:/usr/local/bin/tcsh

 

 

 

q2.shell

 

#! /bin/sh
subject="$1"
letter=$2
shift
shift
for i 
do
     

 

 

 

 

 

Mail -s "$subject" $i < $letter

done

 

Question 3:  20 points

Write a program called q3 with following syntax:

 

 q3   <command>

 

The program uses curses to display the following message in the middle of the screen (assuming  /dev/tty has 20 rows and 80 columns).

 

          Hello <user>, it costs $100, would you like to start (Y/N):

 

The program executes the <command> only if the answer is Y.

 

Example:

 

Assume user wahab types:

 

% q3 draw3cbs

 

The program display:

 

 Hello wahab, it costs $100, would you like to start (Y/N):

 

Answering Y the program executes draw3cbs

q3:

 

 

Question 4:  20 points

Repeat Question 3 using motif  interface instead of curses.

q4:

 

Question 5:  20 points

Modify the following program to draw rectangles instead of lines.

The 1st  click draws point, the 2nd click draws a line between 2nd and 1st 

while the 3rd click draws two lines:  one line from 3rd to 1st and another line from 3rd to 2nd.

q5.c

 

main (argc, argv)

     int argc;

     char **argv;

{

  Display *display;

  Window root, window;

  long fgcolor, bgcolor;

  int screen;

  int x1, y1, x2, y2;

  int count = 1;

  long eventmask = ButtonPressMask | ExposureMask | KeyPressMask;

  XEvent event;

  XGCValues gcval;

  GC draw;

  Colormap cmap;

  XColor color, ignore;

  char *colorname = "Navy";

 

  display = XOpenDisplay (argv[1]);

 

  root = RootWindow (display, screen = DefaultScreen (display));

  fgcolor = BlackPixel (display, screen);

  bgcolor = WhitePixel (display, screen);

 

  window=XCreateSimpleWindow(display,root,0,0,400,400,2,fgcolor,bgcolor);

 

  cmap = DefaultColormap (display, screen);

  XAllocNamedColor (display, cmap, colorname, &color, &ignore);

  fgcolor = color.pixel;

  gcval.foreground = fgcolor;

  gcval.background = bgcolor;

  gcval.line_width = 5;

  draw = XCreateGC(display,window,GCForeground|GCBackground|GCLineWidth, &gcval);

 

 

 

  XSelectInput (display, window, eventmask);

  XMapWindow (display, window);

 

  for (;;)

    {

      XWindowEvent (display, window, eventmask, &event);

      switch (event.type)

      {

      case Expose:

        XClearWindow (display, window);

        break;

      case ButtonPress:

        if (count == 1)

          {

            count = 2;

            x1 = event.xbutton.x;

            y1 = event.xbutton.y;

            XDrawPoint (display, window, draw, x1, y1);

          }

        else if (count == 2)

          {

            count = 1;

            x2 = event.xbutton.x;

            y2 = event.xbutton.y;

            XDrawLine (display, window, draw, x2, y2, x1, y1);

          }

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

        break;

      case KeyPress:

        exit (0);

      default:

        fprintf (stderr, "Unexpected event: %d\n", event.type);

      }

    }

}