Chapter 1

Question 1

List Files and Directories

Answer 1

ls

Question 2

List All Files

Answer 2

ls -a

Question 3

List Files in Long Form

Answer 3

ls -l

Question 4

List Files with Human Readable Sizes

Answer 4

ls -h

Question 5

List files, sorted by size

Answer 5

ls -S

Question 6

List files, sorted by last modified time

Answer 6

ls -t

Question 7

List files, reverse sorted

Answer 7

ls -r

Question 8

Hard links vs a symbolic link?

Answer 8

Hard links create an identical copy of the linked file on disk, that gets updated automatically as the source file gets updated. That means if the content of the source is changed, so will the target file.

Unfortunately hard links do not work for directories. To create a link to a directory, we can use the -s flag to create a symbolic link. This can also be used for linking to files as well, not just directories.

Symbolic links can also link to files or directories on other file systems.

Question 9

Link from source to linked file

Answer 9

ln a.txt b.txt

Question 10

Force a link to be created

Answer 10

ln -f a.txt b.txt

Question 11

Create a symbol link

Answer 11

ln -s a.txt b.txt

Question 12

Navigate up a directory

Answer 12

cd ..

Question 13

Navigate to home directory

Answer 13

cd

Question 14

Create a directory

Answer 14

mkdir foo

Question 15

Create intermediate directories

Answer 15

mkdir -p a/b/c

Question 16

Create directory with verbose output (useful in shell scripts)

Answer 16

mkdir -v a

Question 17

Copy a single file

Answer 17

cp a.txt b.txt

Question 18

Copy multiple files

Answer 18

cp a.txt b.txt foo
or
cp *.txt foo

Last argument must be a directory

Question 19

Copy with verbose output

Answer 19

cp -v a.txt b.txt

Question 20

Copy a directory’s contents

Answer 20

cp -R foo bar

Question 21

Force copying of a file, e.g. if you don’t have permission to do so.

Answer 21

cp -f a.txt b.txt

Question 22

Copy with confirmation of overwriting each file

Answer 22

cp -i a.txt b.txt

Question 23

Delete a file, with verbose output

Answer 23

rm -v a.txt

Question 24

When would you use cp followed by rm, instead of only mv?

Answer 24

This can be useful when trying to move a file across file systems, as the mv command doesn’t support that.

Question 25

How would you find all the files in your home directory that contain an underscore?

Answer 25

ls -a ~ | grep _

Question 26

How would you write output from a command to a file?

Answer 26

ls -a ~ | grep _ > underscores.txt

Question 27

How would you read from a file and send it to a command?

Answer 27

cat