Environment Variables, Aliases

Question 1

When performing a long listing what do the objects show?

Answer 1

permissions links owner group size datemodified file/directory
i.e drwxr-xr-x. 2 cloud_user cloud_user 6 Oct 15 16:20 Desktop

Question 2

How do you list files/directories?

Answer 2

ls

Question 3

How do you list files/directories in order of size?

Answer 3

ls -S

i.e ls -lS

Question 4

How do you do a detailed listing of files/directories?

Answer 4

ls -l

Question 5

How do you do a reverse listing?

Answer 5

ls -r

Question 6

How do you list a directory including its contents?

Answer 6

ls -R

Question 7

How do you list in order of modification time?

Answer 7

ls -t

Question 8

How do you get a listing of environment variables?

Answer 8

env

Question 9

How do you view the directory locations bash will look in when entering a command?

Answer 9

echo “$PATH”

contained in the PATH environment variable

Question 10

How do you reference something in the current directory?

Answer 10

.

i. e ./script1
* dot source

Question 11

What is the command to list the current user?

Answer 11

whoami

Question 12

What is the command to switch user?

Answer 12

su

i.e su user2

Question 13

What is the command to switch the the root user?

Answer 13

su - *resets env variables

su *just switches user

Question 14

What is the command to run as root interactively without the root password?

Answer 14

sudo -i

*useful if no root password exists (common)

Question 15

What is the command to print the name of the OS?

Answer 15

uname

-r release -v kernel build -m/-p architecture -o os name -a all

Question 16

What is the command to print the current working directory?

Answer 16

pwd

echo “$PWD”

Question 17

What is the command to change to the home directory?

Answer 17

cd

cd ~

Question 18

What is the command to change a directory up once

Answer 18

cd ..

Question 19

What is the command to return to the previous directory?

Answer 19

cd -
*used OLDPWD env variable
echo $OLDPWD

Question 20

What is the command to print a history of commands typed?

Answer 20

history

*located in ~/.bash_history

Question 21

What is the command to print the contents of a file to the screen?

Answer 21

cat

Question 22

How do you see the maximum commands the history file will store?

Answer 22

echo $HISTFILESIZE

Question 23

How do you see the configuration of the history command?

Answer 23

echo $HISTCONTROL

i.e ignoredups *ignores consecutively repeated commands

Question 24

How do you execute a specific command in denoted in history?

Answer 24

!

i.e !14

Question 25

What configuration scripts are executed upon signing in through the login shell?

Answer 25

1 /etc/profile - sets up environment variables
2 ~/.bash_profile | ~/.bash_login | ~/.profile - first file executed, sets up user env variables
3 ~/.bashrc - sets up user created functions and command aliases
4 /etc/bashrc - sets up system wide functions and command aliases

Question 26

What script will be executed at user logout if it exists?

Answer 26

~/.bash_logout

*user defined commands can be placed here to perform actions at logout

Question 27

What configuration scripts are executed upon opening a non login shell (standard)?

Answer 27

1 ~/.bashrc - sets up user created functions and commands

2 /etc/bashrc - sets up system wide functions and command aliases

Question 28

How do you modify the $PATH env variable?

Answer 28

append: PATH=$PATH:/directory
prepend: PATH=/directory:$PATH

Question 29

How do you create a variable and use it in other shells?

Answer 29

export VARIABLENAME

Question 30

What is the structure that constitutes a command?

Answer 30

Command Option Argument

i.e ls -l file

Question 31

What is the command to create an alias?

Answer 31

alias =’’

i.e alias lr=’ls -R’

Question 32

What is the command to remove a created alias?

Answer 32

unalias

i.e unalias lr

Question 33

How do you create a persistent alias?

Answer 33

Append alias to ~/.bashrc

Question 34

How do you get a listing of shell and environment variables?

Answer 34

set