Homework Quiz Questions

Question 1

Linux is a free operating system developed for the __________
processor that is intended to replicate the functionality of ________

Answer 1

80X86, Unix

Question 2

Linux was first released by ___________ , who was a student at University of Helsinki at the time.

Answer 2

Linus Torvalds

Question 3

C was developed at _________ in the early 1970’s simultaneously with
_______.

Answer 3

Bell Labs, Unix

Question 4

The command ____________ prints the absolute path to your current working directory.

Answer 4

pwd

Question 5

The ____________ command is used to change permissions on a file.

Answer 5

chmod

Question 6

________ changes the working directory to the root directory

Answer 6

cd /

Question 7

________ changes the working directory to the user’s home without using tilde expansion.

Answer 7

cd

Question 8

______ changes the working directory to the user’s home directory using tilde expansion.

Answer 8

cd ~

Question 9

______ changes the working directory to the user bob’s home directory using tilde expansion.

Answer 9

cd ~bob

Question 10

Explain the differences between a static C library and a C shared library

Answer 10

Static libraries are libraries that can be used in multiple programs, inside of a program when it is compiled. Conversely, shared libraries exist completely separate from the compiled program as a separate file or files

Question 11

Write a command that assigns the value “CSI 3336” to an environment variable named classNumber.

Answer 11

classNumber=”CSI 3336”

Question 12

Write a command that assigns the value “Systems Programming” to an environment variable named className.

Answer 12

className=”Systems Programming”

Question 13

Write a command that concatenates the values found in classNumber and className into a new environment variable named class

Answer 13

class=”$classNumber$className”

Question 14

Write a command that lists the directory contents of the local directory and all subdirectories.

Answer 14

ls -r

Question 15

Write a command that creates a new directory named cs3336 in the current working directory.

Answer 15

mkdir cs3336

Question 16

Write a command that displays the current system time.

Answer 16

date

Question 17

Write a command that changes the permissions of a file named output rwxr-xr— using octal numbers in combination with chmod.

Answer 17

chmod 754 output

Question 18

Write a command that changes the permissions of a file named output rwxr-xr— using characters (not octal numbers) in combination with chmod (without octal numbers).

Answer 18

chmod u=rwx,g=rx,o=r output

Question 19

Write a command that displays all exported environment variables

Answer 19

env

Question 20

Explain what cat does

Answer 20

cat reads the files you provide and writes them out sequentially to stdout. It can be used to quickly examine the contents of a file, or a few small files.

Question 21

Explain what less does

Answer 21

less is a quicker version of more. It displays the contents of a file in a page-by-page format, but doesn’t load the whole file at once which makes it faster. This makes it a much better option for just viewing files than opening them up in something like vi or vim.

Question 22

Write a command that displays the first 5 lines of a file named classList.txt.

Answer 22

head -n 5 classList.txt

Question 23

Write a command that displays the last 10 lines of a file named classList.txt.

Answer 23

tail -n 10 classList.txt

Question 24

Write a command that changes the status time (this includes access, modify, and change times) of a file named myFile to the current system time.

Answer 24

touch myFile

Question 25

Write a command that removes all files in the current directory that end with .del

Answer 25

rm *.del

Question 26

What command can be used to copy files from one system to another (e.g. your local computer to the department Linux boxes)?

Answer 26

scp

Question 27

Explain how bash manages execution of commands with regards to processes.

Answer 27

When a command is executed, a new child process is created and put in the foreground. Other processes are put in the background. You can switch between these different commands being executed similarly to switching tabs on a computer by moving processes to the foreground/background.

Question 28

Provide the proper filename expansion for the following (assume local directory) for all files ending in .sh

Answer 28

*.sh

Question 29

Provide the proper filename expansion for the following (assume local directory) for all files beginning with assign

Answer 29

assign*

Question 30

Provide the proper filename expansion for the following (assume local directory) for all files beginning with assign, containing any number of characters, and ending with .tar.gz.

Answer 30

assign*.tar.gz

Question 31

Provide the proper filename expansion for the following (assume local directory) for all files beginning with assign, containing a single digit, and ending with .tar.gz.

Answer 31

assign[0-9].tar.gz

Question 32

Provide the proper filename expansion for the following (assume local directory) for all files in bob's home directory ending with .csv.

Answer 32

~bob/*.csv

Question 33

Provide the proper regular expression (regex) for the following (assume single match per line) for all items that contain the string "file".

Answer 33

.*file.*

Question 34

Provide the proper regular expression (regex) for the following (assume single match per line) for all items that begin with the string "file".

Answer 34

^file.*

Question 35

Provide the proper regular expression (regex) for the following (assume single match per line) for all items that end with the string "ing".

Answer 35

.*ing$

Question 36

Provide the proper regular expression (regex) for the following (assume single match per line) for all items that contain the same 4 or 5 letter sequence twice.

Answer 36

.*([a-zA-Z]{4,5}).*\1

Question 37

Provide the proper regular expression (regex) for the following (assume single match per line) for all items that starts with a number (multiple digits possibly) immediately followed by a colon (don't worry about 0: )

Answer 37

^[0-9]+:

Question 38

Provide a one-liner to print all processes being run by the first user listed by who.

Answer 38

ps -u `who | head -n 1 | sed "s/ .*//"`

Question 39

Provide a one-liner to send email with the subject, "welcome", to all users listed in a tab delimited file, named "folks.csv" (the third value in the record is the email address). The body for the email is found in a file named "welcome".

Answer 39

awk -F'\t' '{print $3}' folks.csv | xargs -I{} mail -s "welcome" {} < welcome

Question 40

What must be provided to execute a program located in the local directory (assuming the local directory is not in the path and the file is set as executable)? Why?

Answer 40

./ must be provided before the filename. This is because the shell only searches for executable files in the PATH, so it won't be able to find anything outside of the PATH without some kind of explicit instruction. The ./ tells the shell that the executable file is in the current directory. This is done for security as files outside the PATH could be tampered with, so it is best to make sure what you are executing is something that you have cleared and put in your PATH, or are sure that you are running from the current directory.