Command Line

Question 1

Prompt

Answer 1

$

For Amazon Linux

Question 2

Cursor

Answer 2

Where anything typed will show up

Question 3

echo

Answer 3

display text in output

Question 4

pwd

Answer 4

present working directory

Question 5

command format

Answer 5

[command] [arguments…]

Question 6

man [command]

Answer 6

Displays manual for [command]

Type “q” to exit manual.

Question 7

Command Line Uses

Answer 7

Restart servers
Rename hundreds or thousands of files according to a prescribed pattern
Manage system logs
Set up scheduled tasks (cron jobs)
Debug server issues
Monkey patch code on a server
Query data
Set up databases and servers
--- and many more

Question 8

cd [directory]

Answer 8

change directory

by itself, changes to the home directory, and with argument goes to the indicated directory

Question 9

ls

Answer 9

list files and directories in current directory

Question 10

pwd

Answer 10

display the path of the current directory

Question 11

touch

Answer 11

create a file

Question 12

mkdir

Answer 12

make directory

Question 13

rm

Answer 13

remove a file or directory

Is permanent!

Question 14

cp

Answer 14

copy a file or directory

Question 15

mv [source] [destination]

Answer 15

move or rename a file or directory
movement is relative to current directory
.. = parent directory
. = current directory
/[directory name] = child directory

Question 16

cat

Answer 16

display contents of a file

Question 17

more

Answer 17

displays contents of a file, starting at the top and letting the user scroll down

Question 18

less

Answer 18

display contents of a file in an even ore interactive way

Question 19

head

Answer 19

displays first part of a file

Question 20

tail

Answer 20

displays last part of a file

Question 21

cd /

Answer 21

change to parent directory

Question 22

ls -1

Answer 22

lists files and directories in the current directory, each on a new row of output

Question 23

cd ~

Answer 23

change to home directory

cd $HOME also works

Question 24

q

Answer 24

exit current screen, eg “man”, “more”, etc.

Question 25

clear

Answer 25

clears current output screen

Question 26

/

Answer 26

root directory, or separator for listing directories

Question 27

, or ./

Answer 27

current directory

Question 28

.. or ../

Answer 28

parent directory

Question 29

../..

Answer 29

grand parent directory

Question 30

*

Answer 30

wildcard

Question 31

ls -a

Answer 31

includes hidden files in list

“ ls -d .* “ lists only the hidden files

Question 32

ls -lah

Answer 32

Get detailed information about the files and directories listed

Question 33

which [command]

Answer 33

shows the directory where the executable exists for the [command]

Question 34

env

Answer 34

display environment variables and values

Question 35

variable=”value”

Answer 35

how to set an environment variable value

note that there are no spaces

Question 36

ps1

Answer 36

environment variable for the prompt

Question 37

.bashrc, .bash_profile

Answer 37

environment files (for bash, not Zsh)
nano ~/.bashrc to edit

Question 38

bin

Answer 38

binary: executable file

Question 39

PATH

Answer 39

environment variable.
determines which directories are searched when a command is entered
an ordered, colon-delimited list of directories that contain executables
PATH can be amended to add directories for executables
to permanently change PATH: .bashrc

Question 40

rwx

Answer 40

read, write, exectute

Question 41

drwxrwxr-x 3 ec2-user ec2-user practice

Answer 41

rwx = read, write, execute
d | rwx | rwx | r-x | 3 |ec2-user | ec2-user | practice
directory | User wx | Group rwx | Other rwx | # files | user name | group name | file / directory name

Question 42

chmod u-w test.txt

Answer 42

add write permissions for user to file test.txt

Question 43

chmod 777 text.sh

Answer 43

set permissions on text.sh to read, write, and execute for all users, groups, others.
Number	Permission
0	No permission granted.
1	Can execute.
2	Can write.
3	Can write and execute (2 + 1 = 3).
4	Can read.
5	Can read and execute (4 +1 = 5).
6	Can read and write (4 + 2 = 6).
7	Can read and write and execute (4 + 2 + 1 = 7).

Question 43

chmod 777 text.sh

Answer 43

set permissions on text.sh to read, write, and execute for all users, groups, others.
Number Permission
0 No permission granted.
1 Can execute.
2 Can write.
3 Can write and execute (2 + 1 = 3).
4 Can read.
5 Can read and execute (4 +1 = 5).
6 Can read and write (4 + 2 = 6).
7 Can read and write and execute (4 + 2 + 1 = 7).

Question 44

groups

Answer 44

display the groups for current user

Question 45

su

Answer 45

switch user

su - = switch to root user, password entry may be required

Question 46

REPL

Answer 46

Read-Eval-Print-Loop