exam 2 practice

Question 1

Say the critical section is protected by the exitSemaphore. When a thread finishes its critical section, it signals this by calling sem_post(&exitSemaphore)

true or false

Answer 1

true

Question 2

The ___________ function is used to create a socket (communication endpoint) and returns a file descriptor that can be used for further socket operations.

Answer 2

socket()

Question 3

After a successful dup2() call, what is the relationship between oldfd and newfd?

Answer 3

They refer to the same file

Question 4

When is atomicity guaranteed for the write() operation?

Answer 4

For requests with a size typically around 4096 bytes or less

Question 5

What does the pipe() system call return if an error occurs during its execution?

Answer 5

-1

Question 6

What is the general syntax of the pipe() system call?

Answer 6

int pipe(fd[2]);

Question 7

fputc() is used for buffered character output (it writes a character to a specified file stream and allows buffering for improved performance) but putc() is a more general function and can be used for unbuffered character output or buffered character output depending on the file stream
true or false

Answer 7

True

Question 8

Why is the gets(theBuffer) function considered a high-security risk?

Answer 8

It can overwrite memory and lead to buffer overflow vulnerabilities.

Question 9

A thread can be bound to multiple processes.

Answer 9

False

Question 10

In blocking I/O, a program waits for the operation to complete and can be delayed, potentially causing slower performance.

Answer 10

True

Question 11

After a successful call to execv (Select all that apply)

Answer 11

-instructions are executed at the beginning of main()
-an executable specified as an argument to execv is loaded

Question 12

A deadlock might occur when one thread tries to send a message from user A to user B while another tries to send a message from user B to user A

Answer 12

True

Question 13

____________ and ____________ are custom signals that can be used for user-defined purposes, such as triggering specific actions within a process.

Answer 13

SIGUSR1 and SIGUSR2

Question 14

ssh and http can be implemented using this socket type.

Answer 14

a connection-oriented socket like TCP

Question 15

Select the true statements about stream sockets

Answer 15

-Data arrives in the form of a byte-stream
-Receiver needs to separate messages in stream
-There is no requirement to segment the data into packets.
-Data transfer happens using send() and recv() functions

Question 16

What happens in the following code?

unsigned short val = 0x01FF;
printf(“%u\n”,val);

The printed value will be ___________

Answer 16

511

Question 17

Which parameter specifies the maximum number of established connections waiting to be accepted (using accept()) in conjunction with the listen() function?

Answer 17

backlog

Question 18

Which function translates a host name to an IP address?

Answer 18

gethostbyname

Question 19

Choose the correct statements about select()

Answer 19

Waits on multiple file descriptors/sockets and timeout
-Application does not consume CPU cycles while waiting
-Returns when file descriptors/sockets are ready to be read or written or they have an error or timeout exceeded
-Has a disadvantage that it does not scale to large number of file descriptors/sockets

Question 20

In a C program, when should you use fflush(stdout);?

Answer 20

To ensure that any buffered output to the standard output (stdout) is immediately written to the screen.

Question 21

When should IO multiplexing be used?

Answer 21

When you need to handle concurrent I/O operations, such as reading from or writing to multiple sockets or files.

Question 22

The following happens in sem_post(sem_t *sem);

Answer 22

sem_post() increments (unlocks) the semaphore pointed to by sem
- it returns a zero on success
-if the semaphore’s value becomes greater than zero as a result of sem_post() then another thread blocked in a sem_wait() call will be woken up to lock the semaphore

Question 23

This signal cannot be ignored or blocked

Answer 23

SIGKILL

Question 24

What is the primary purpose of the SIGHUP signal in Unix-like operating systems?

Answer 24

Notify a process of changes in terminal status or disconnect

Question 25

Choose the CPU-bound processes among these choices

Answer 25

-mathematical computations -image and video processing -scientific applications -data analysis

Question 26

The function of a block special file is to provide access to the hard drive device in fixed-size blocks or chunks, each typically consisting of multiple bytes.

Answer 26

True

Question 27

What is the primary responsibility of a thread manager in a multithreading environment?

Answer 27

Coordinating the creation, scheduling, and termination of threads

Question 28

Consider the following code segment: int main() { if (fork() > 0) sleep(100); return 0; } Execution of this code could result in the creation of a(n)

Answer 28

zombie process

Question 29

header defines the various data types used in socket related functions. Choose the common types you encounter here.

Answer 29

-ssize_t -socklen_t -size_t -pid_t

Question 30

In Unix-like file systems, what does the execute permission (x) on a file indicate for a user?

Answer 30

The user can execute the file as a program

Question 31

What is the octal code for granting read and write permissions to the owner, read-only permission to the group, and no permission to others on a file in a Unix-like file system?

Answer 31

640

Question 32

Which of the following statements about mutex locks is true?

Answer 32

Mutex locks are only used for thread synchronization within a single process

Question 33

A socket system call returns _______ for the created socket

Answer 33

A file descriptor