The Shell: Practice Questions

For each snippet, write the output of its final command. If it prints nothing, write “No Output”.

Each snippet starts in a new, empty directory.

For Git questions, assume git init starts on main and commits succeed.

Question 1

echo 'hello world' >> README
echo 'hola mundo' > README
echo 'salve munde' >> README
cat README | wc -l

Answer

2

Question 2

echo 'hello world' >> README
echo 'hola mundo' >> README
echo 'salve munde' >> README
wc -l README

Answer

3 README

Question 3

echo 'hello world' > README
echo 'hola mundo' >> README
echo 'salve munde' > README
wc -l < README

Answer

1

Question 4

echo 'x = 1' >> example.py
echo 'x += 1' >> example.py
echo 'print("x=", x)' >> example.py
python3 example.py

Answer

x= 2

Question 5

echo 'xs = [1, 2]' >> example.py
echo 'xs.append(5)' >> example.py
echo 'print("xs=", xs)' >> example.py
python3 example.py

Answer

xs= [1, 2, 5]

Question 6

python3 <<EOF
x = 1
x += 1
print("x=", x)
EOF

Answer

x= 2

Question 7

cat > example.py <<EOF
x = 1
x += 1
print("x=", x)
EOF
python3 example.py

Answer

x= 2

Question 8

cat > example.py <<ROFL
x = 1
x += 1
print("x=", x)
ROFL
python3 example.py

Answer

x= 2

Question 9

cat > example.py <<EOF
import sys
print("sys.argv=", sys.argv)
EOF
python3 example.py hello world

Answer

sys.argv= ['example.py', 'hello', 'world']

Question 10

cat > example.py <<EOF
import sys
print("sys.argv=", sys.argv)
EOF
python3 example.py "hello world"

Answer

sys.argv= ['example.py', 'hello world']

Question 11

cat > example.py <<EOF
import sys
print("sys.argv=", sys.argv)
EOF
python3 example.py 'hello world'

Answer

sys.argv= ['example.py', 'hello world']

Question 12

cat > example.py <<EOF
import sys
num_args = len(sys.argv)
print("num_args=", num_args)
EOF
python3 example.py "salve munde" "hola mundo"

Answer

num_args= 3

Question 13

cat > example.py <<EOF
import sys
num_args = len(sys.argv)
print("num_args=", num_args)
EOF
python3 example.py "salve munde' 'hola mundo"

Answer

num_args= 2

Question 14

cat > example.py <<EOF
import sys
num_args = len(sys.argv)
print("num_args=", num_args)
EOF
python3 example.py

Answer

num_args= 1

Question 15

touch hello_world
touch hola_mundo
touch salve_munde
ls | wc -l

Answer

3

Question 16

touch 'hello world'
touch "hola mundo"
touch salve munde
ls | wc -l

Answer

4

Question 17

touch 'hello world' hola "mundo salve munde"
ls | wc -l

Answer

3

Question 18

export password="hello world"
cat > quiz.py <<'EOF'
import os
print(os.getenv('password', 'hola mundo'))
EOF
python3 quiz.py

Answer

hello world

Question 19

export password=hello
cat > quiz.py <<'EOF'
import os
print(os.getenv('password', 'hola'))
EOF
python3 quiz.py

Answer

hello

Question 20

export PASSWORD=hello
cat > quiz.py <<'EOF'
import os
print(os.getenv('password', 'hola'))
EOF
python3 quiz.py

Answer

hola

Question 21

touch README
echo 'API_KEY=asd' > .env
ls -1

Answer

README

Question 22

touch README
echo 'API_KEY=asd' > .env
ls -1a

Answer

.
..
.env
README

Question 23

touch README
mkdir test
touch test/README
cd test
echo 'API_KEY=asd' > ../.env
ls -1a

Answer

.
..
README

Question 24

touch README
mkdir test
mkdir test/test
touch test/README
touch test/test/README
cd test/../test
ls | wc -l

Answer

2

Question 25

touch README
mkdir test
cd test
mkdir test
touch README
cd ..
touch README
ls | wc -l

Answer

2

Question 26

touch README
mkdir test
touch test/README
touch test/.env
ls -a test | wc -l

Answer

4

Question 27

touch README
mkdir test
touch test/README
touch test/.env
ls test | wc -l

Answer

1

Question 28

touch README
mkdir test
mkdir test/test
touch test/README
touch test/test/README
cd test/../test
ls . | wc -l

Answer

2

Question 29

touch README
mkdir test
mkdir test/test
touch test/README
touch test/test/README
cd test/../test
ls .. -a | wc -l

Answer

4

Question 30

git init
touch README
mkdir foo
touch foo/README2
touch README3
ls foo | wc -l

Answer

1

Question 31

git init
touch README
mkdir foo
touch foo/README2
touch README3
ls -a foo | wc -l

Answer

3

Question 32

git init
touch README
mkdir foo
touch foo/README2
touch README3
ls -a . | wc -l

Answer

6

Question 33

git init
mkdir master
echo "print('hello world')" > master/foo.py
echo "print('hola mundo')" > foo.py
git add master
git commit -m "added master"
git branch foo
git checkout foo
echo "print('hola mundo')" >> foo.py
git add foo.py
git commit -m "modified foo"
git checkout main
ls -1

Answer

master

Question 34

git init
echo "print('hello world')" > foo.py
echo "print('hola mundo')" > bar.py
git add foo.py
git commit -m "added foo"
git branch foo
git checkout foo
echo "print('hola otra vez')" >> foo.py
git add foo.py
git add bar.py
git commit -m "modified foo"
git checkout main
echo "print('hello again')" >> bar.py
python3 bar.py

Answer

hello again

Question 35

git init
echo "print('hello world')" > foo.py
git add foo.py
git commit -m "added foo"
git branch foo
git checkout foo
echo "print('hola mundo')" >> foo.py
git add foo.py
git commit -m "modified foo"
git checkout main
python3 foo.py

Answer

hello world