CS332 Test 2

What does a File Descriptor do?

It keeps track of the open files within linux, each file is labeled by a number

T/F: File Descriptors can be negative ints

False

What is the standard I/O stream

The standard I/O stream allows you to open a file in read, write or append modes

What is the input stream?

The I/O stream that allows for the program to open a file.

What is the output stream?

The I/O stream that allows a program to write to a file

What does the function 'getc()' do?

It lets you get the next character from an input stream

What does the function getline() do?

It lets you get an entire line from the input stream, it also stores the address of the buffer

T/F: the getline() returns the terminating null byte ('\\0')

False

What does getdelim() do?

It gets the characters present upto the delimiter

T/F: the getdelim() returns the terminating null byte ('\\0')

False

What does the function gets() do?

It reads a line from the input stream and stores it into the string pointed to by a str

When does the function gets() stop?

It stops whenever a newline ('\\n') or the end of file is reached

To avoid buffer overflow, one should use ______ instead of gets() in order to restrict how many characters are read

fgets()

strtok is responsible for?

extracting tokens from strings. It breaks down a string into a string of zero or more nonempty tokens

atoi, atol, atoll are all responsible for?

converting a string to an integer

atof is responsible for?

converting a string to a double

strdup is responsible for?

duplicating a string

A program in execution is also known as a _____

process

An instance of a running program is also known as _____

process

The entity that can be assigned to, and executed on, a processor is also known as ______

process

A unit of activity characterized by a single sequential thread of execution, a current state, and an associated set of system resources can also be known as ______

process

When a program is loaded into the memory, it can be divided in the sections of

stack

heap

text

data

The data section of memory in a x86-64 linux machine is responsible for?

holding statically allocated data, such as global vars, static vars, and string constants

The heap section of memory in a x86-64 linux machine is responsible for?

it holds variables/objects that are dynamically allocated whenever you use things such as malloc, calloc, new

The stack section of memory in a x86-64 linux machine is responsible for?

holding runtime variables such as local variables

The text section of memory in a x86-64 linux machine is responsible for?

holding executable machine instructions and it is read-only

when a program is executing, the process can be uniquely characterized by how many number of elements?

8 elements

What are the 8 elements that can uniquely characterize a program process

identifier

state

priority

program counter

memory pointers

context data

I/O status information

accounting information

process spawning is the act of?

when an OS creates a process at the explicit request of another process

the parent process is known as the

original process

T/F: when a parent process creates a new process, it is a copy of the parent process

true

T/F: In process termination, there must be a means for a process to indicate it's completion

true

T/F: In process termination, there can be a batch job that includes a HALT instruction or an explicit OS service call for termination

true

For an interactive application, what indicates the process is completed?

The actions of the user, such as logging off, quitting an application, etc

The two modes of execution are ___________ mode and ___________ mode

user, system

User programs generally execute in ______ mode

user

T/F: System mode is an elevated mode of running executables

true

PID stand for?

process ID

the OS tracks processes through a _________

five digit ID (aka, PID)

T/F: Each process in the system has a unique PID

true

the 'ps' command showcases?

a list of running processes

a background process is a process that?

\n runs in the background, frees the terminal for user control but continues to run without user input

a foreground process is a process that?

runs in the foreground, it attachs directly to the current view of the user for the terminal thus a user can interact with it directly

how do you bring a background process to the foreground?

fg %

how do you send a foreground process to the background

suspend the process, then use bg or if the program is not suspended you can use bg %

how do you start a program in the background?

use '&', &

how does fork() work

it creates a new process by duplicating the calling process. The new process is referred to as the child process. The calling process is referred to as the parent process.

the newly created process after running fork() is called?

the child process

T/F: after the parent process creates the child process, the parent process continues with its normal execution

true

what happens to a child process if the parent process terminates before it

it becomes a zombie process

what is a zombie process

a process without a parent process

the wait() function allows for the child process to exit prior to the parent process by ___________ the parent process

suspending

when do you use waitpid() vs using wait() to watch for a change of state in a child process

whenever you have more than one child process and you want to track a specific one

the exec() family of function is responsible for

replacing the current process image with a new process image

what does the execl() function take as an argument

the execl() function take the full pathname of executable along with a pointer to an array of characters for each argument

There are _______ classes of exec functions

two

The two classes of exec functions are ____ and ____

l versions, v versions

What's the difference between l versions and v versions for the exec() family of functions

the l versions take a list as an argument while the v version takes a vector as the arguments

T/F: The l versions of functions within the exec family end their list of arguments with a null pointer

true

T/F: The v versions of functions within the exec family end their list of arguments with a null pointer

false

Functions that have a p at the beginning of the name use the ____________ as the first argument

filename

Functions without the a p at the beginning of the name use _____________ as the first argument

pathname

T/F: if the filename contains a slash character (/) it is considered as a pathname

true

function that end in e have an additional argument, a point to an array of pointers to the _________________ strings

environment

The environment is defined by the _________________ variables

environment

The environment variables can be set by __________ or ____________ or _______________ or ___________

The system

The user

The shell

Programs that loads other programs

In unix shells the act of initialization refers to

the setup of the environment, using environment variables to customize how the system works and the behavior of applications on the system

T/F: Linux and Unix are the same

False

Linux is derived from _______

unix

T/F: Linux refers to a complete OS

False

Linux is just a _______

kernel

This Linux kernel is generally packaged in Linux ___________ which thereby makes it a ___________ ____

distributions , complete, OS

The three states a user process in a linux environment are __________ , ____________ or ____________

foreground

background

suspended

interactive applications can only run in the _____________ state

foreground

if you are running a non-interactive process, it is best you run it in the ________

background

to execute a program in the background, you use the following syntax

&

when you start a program in the background, the shell will return the

The background process number and the corresponding process identifier

To view background processes you run the _____ command

jobs

to suspend a foreground process you press

control-z

background processes that start when the system start and end when the system ends are called?

daemons

generally daemon process end in which character ?

d

to terminate a foreground process you press

control-c

to terminate a background process you can _______ or you can _______

bring to foreground and use control-c

\
use the kill command

the argument for the kill command is the

PID of the process you would like to terminate

the ps command is responsible for

reporting a snapshot of the current process

By default, ps lists processes for the

current user associated with the terminal that invoked it

the ps snapshot includes

the process ID (PID), the terminal associated with the process (TTY), the cumulative CPU time in hh:mm:ss format (TIME), and the executable name (CMD)

The pstree command is used to display the ______ _______

process tree

the process tree is

a tree view of the processes running sorted by PID

the ______ command does the same thing as the ps command

top

what's the difference between the top command and the ps command

the top command showcases a real-time update while ps showcases a snapshot

a virtual file system that is created by the OS at system boot time to provide an interface between the kernel space and user space is called the

proc file system

the /proc file system is responsible for

providing information of processes currently running on the system and tools such as ps use this to display information about these processes

For files that contain strings separated with null characters you have to use the ________ command to display the contents of such files correctly

strings

the unit of dispatching is reffered to as a ______________ or ________________

thread, lightweight process

the unit of resource ownership is reffered to as a ___________ or _________

process, task

multithreading is the ability of an OS to

support multiple, concurrent paths of execution within a single process

T/F: each thread belongs to exactly one process and no thread can exist outside a process

true

each thread represents ___________

a separate flow of control

concurrency

the ability of different parts or units of a program to be run out-of-order or in partial order without affecting the final outcome