Command Line Basics

Question 1

What is the $ in the command line?

Answer 1

It is the prompt or command prompt

Question 2

What is the command line?

Answer 2

A user interface that’s navigated by typing
A way to interact with the computer using text and keywords

Question 3

The command for the current machine and user name

Answer 3

Windows 10
$ whoami
scratchnsniff\jesse agar

Cloud 9
$ whoami
Ec2-user

Question 4

Where does just the command cd take you?
What’s the difference between root, home, and user’s home and how do you get to each place

Answer 4

Takes you to user’s home direction (not the home folder)
Same as going
$ cd ~

The directory contains everything.
/home/user (c9 takes you to user when going “home”)
Including the home directory. Every user has their own home directory that contains pictures, music, personal files etc.

Root
cd /

Home
cd /home

User’s Home
cd ~
or
cd

Question 5

Show files in current directory

Answer 5

$ ls

Question 6

Show hidden files and folders
Show only hidden files and folders

Answer 6

$ ls -a
$ls -d .*

Question 7

Show longform info on files and folders
(Shows the following: file mode, number of links, owner name, group name, number of bytes in the file, abbreviated month, day-of-month file was last modified, hour file last modified, minute file last modified, and the pathname)

Answer 7

$ ls -l
l for long form
(l for lots of info)

Question 8

Show longform info on files and folders but with size in kb, mb, and gb as needed rather than just bytes

Answer 8

$ ls -lh
h for Human readable

Question 9

Show files and folders by size

Answer 9

$ ls -s
s for size

Question 10

Show files and folders by date modified

Answer 10

$ ls -t

Question 11

Show files and folders by reversed (of whatever other flags)

Answer 11

$ ls -r

Question 12

Create a file or update it’s date.
How do you do multiple files?

Answer 12

$ touch
‘Touch’ a file in memory. Creates files. Updates their ‘modified date’.
For multiple files separate by space
$ touch index.html script.js style.css

Question 13

Keyword for home directory
Keyword for root directory
Where are they relative to one another

Answer 13

~
/

/home/ec2-user
~ and cd bring you to ec2-user, not home, on C9

Question 14

Keyword for previous directory

Answer 14

..

Question 15

Keyword for current directory

Answer 15

.
Can be used as a shortcut to add everything in this directory:
$ git add .

Question 16

Autocomplete a name in terminal
How does it behave if multiple files have the same common letters?

Answer 16

tab while typing a name
Will complete the directory or filename
It will autocomplete up to the most common letter among the options
If there are no more common letters but multiple options, press tab again and it will show you the options

Question 17

Display name of the current directory

Answer 17

$ pwd

Question 18

Rename a file

Answer 18

mv oldfile.txt newfilename.txt

Also how you move a file

Question 19

Move a file

Answer 19

mv oldfiledirectory.txt newfiledirectory.txt

Also how you rename

Question 20

Create a directory

Answer 20

$ mkdir

Question 21

Create nested directory

Answer 21

Create a series of nested directories
$ mkdir -p directory1/directory2

p for parent

Question 22

Create a directory in the previous directory

Answer 22

$ mkdir ../newdirectory

Question 23

Create directory and print the results of mkdir to console

Answer 23

$ mkdir -v for Verbose

Question 24

Copy a file

Answer 24

$ cp sourcefilename.txt directory/filename2.txt

Question 25

Copy files and prints results to console

Answer 25

$ cp -v

Question 26

Copy directory

Answer 26

$ cp -r

Question 27

Copy and force overwrite (not required for same user)

Answer 27

$ cp -f
Only needed when overwriting the file of another user

Question 28

Copy and prompt overwrite

Answer 28

$ cp -i
i for interactive

Question 29

Delete a file

Answer 29

$ rm

Question 30

Delete a directory

Answer 30

$ rm -r

Question 31

Chain commands, redirect the output of one command into another.

Answer 31

pipe operator
Ex:
ls -a ~ | grep _ | sed “s/_/-/g”
ls all files indirectory
Find files with _
Replace _ with -

Question 32

Write the output of a command to file

Answer 32

> ls -a ~ | grep _ > underscores.txt
Ex:
Listing 1.39: $ cat underscores.txt
.DS_Store
.bash_history
.bash_profile
.guard_history
.pry_history
.psql_history
.rediscli_history
.scala_history

Question 33

Read from file

Answer 33

<
Pipe that information from a file into a command

Question 34

Create an identical copy of a file that gets updated as the source file is updated.

What happens if source file gets deleted?

Answer 34

$ ln sourcefilename.txt targetnewfilename.txt
If source if deleted, target survives as independent file.

Question 35

Force a file to become the backup target of another

Answer 35

$ ln -f
ln sourcefilename.txt targetfilename.txt -f
Overwrites the existing file.

Question 36

Create an identical copy of a file on a different file system and for directories.

Answer 36

Symbolic copy
ln -s a.txt b.txt
Because it works for directories and different file systems, its much more common.

Question 37

Relative vs absolute path

Answer 37

If it starts from root (/) it’s absolute
starting from current location it’s relative.

Question 38

check node version

Answer 38

$ node -v

Question 39

install readline sync so you can have input in JS programs without a browser

Answer 39

$ npm install readline-sync –save

Question 40

Get the manual for a command

Answer 40

$ man (any command)

Question 41

sudo stands for…

Answer 41

superuser do
It’s the master key to your high-privilege admin tasks.

Question 42

Go 2 folders up, 3 folders up

Answer 42

cd ../..
cd ../../..

Question 43

List all files that follow a certain name pattern

Answer 43

use * to indicate any characters or number of characters

Question 44

Copy all the contents of a folder

Answer 44

cp folder/* folder2

Question 45

View a tree view of all folders from the current directory or specific direction

Answer 45

tree
tree folderName

Question 46

list only hidden files
what else does the command do?

Answer 46

ls -d .*

Question 47

what’s the difference between /foldername and foldername/

Answer 47

/foldername is looking at the root directory
foldername/ is looking from the current directory

Question 48

Find an executable’s location

Answer 48

which executable
ex:
which touch