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CS 476/576
Systems Programming
Fall 2008
Final Exam
Time 2 & 1/2 hours
Open Book & Notes

Name:

Unix Login:

Each Question is 20 points.

Question 1:

Consider the following program, called Q1.c and its corresponding code is called Q1

int main(int argc, char **argv)
{
    int n, in, out;
    char buf[1024];

    mode_t mode = S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH;

    in = open(argv[1], O_RDONLY);
    out = open(argv[2], O_CREAT | O_WRONLY | O_APPEND, mode);
    while ((n = read(in, buf, sizeof(buf))) > 0)
        write(out, buf, n);
    lseek(in, 0, SEEK_SET);
    while ((n = read(3, buf, sizeof(buf))) > 0)
        write(4, buf, n);
    close(0);
    close(1);
    dup2(3,0);
    dup2(4,1);
    lseek(in, 0, SEEK_SET);
    while ((n = read(0, buf, sizeof(buf))) > 0)
        write(1, buf, n);
}

% Q1 Q1.c Q1Out

% wc Q1.c

30 87 657 Q1.c

What is the output of:

% wc Q1Out

Question 2:

Consider the following program, called Q2.c and its corresponding code is called Q2

int     count = 0;
void    handler(int);

int main(int argc, char *argv[])
{
   char buf[BUFSIZ];

   signal(SIGALRM, handler);
   signal(SIGINT, handler);
   alarm(2);
   while (count < 2) pause();
}

void handler(int sig)
{
   printf("Got %d: ", sig);
   if (sig == SIGALRM) {
      signal(SIGALRM, handler);
      printf("Timeout\n");
      kill(getpid(), SIGINT);
      alarm(2);
   }
   else {
      signal(SIGINT, handler);
      printf("Interrupt\n");
      count++;
   }
}

% kill –l

HUP INT QUIT ILL TRAP ABRT EMT FPE KILL BUS SEGV SYS PIPE ALRM TERM USR1 USR2 CLD PWR WINCH URG POLL STOP TSTP CONT TTIN TTOU VTALRM PROF XCPU XFSZ WAITING LWP FREEZE THAW CANCEL LOST RTMIN RTMIN+1 RTMIN+2 RTMIN+3 RTMAX-3 RTMAX-2 RTMAX-1 RTMAX

What is the output of:

% Q2

Question 3:

A. Consider the following program, called Q3.c and its corresponding code is called Q3

int I = 0;
int
main (int argvc, char **argv)
{
    printf("I is %d\n", I++);
    fork();
    printf("I is %d\n", I++);
    fork();
    printf("I is %d\n", I++);
}

What is the output of:

% Q3

B. Consider the following program, called Q4.c and its corresponding code is called Q4

int I = 0;
int
main (int argvc, char **argv)
{
    if (argvc > 1) exit(0);
    printf("I is %d\n", I++);
    if(fork()==0)
    execl ("./q4","q4","1", NULL);
    printf("I is %d\n", I++);
    if( fork()==0)
    execl ("./q4","q4", "2",NULL);
    printf("I is %d\n", I++);
}

What is the output of:

% Q4

Question 5:

Change the following program to use TCP connection instead of pipe.

int
main(void)
{
    int pfd[2];
    char line[64];

    pipe(pfd);
    if (fork() == 0) {
        close(pfd[0]);
        dup2(pfd[1], 1);
        close(pfd[1]);
        execl("/bin/date", "date", 0);
    }

    close(pfd[1]);

read (pfd[0], line, sizeof(line)) ;

printf("date from child is: %s\n", line);
}