awk patterns and actions in Linux CLI - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of this awk command?

Given a file data.txt with the following content:

apple 10
banana 20
cherry 30
apple 40

What is the output of this command?

awk '$1 == "apple" {print $2}' data.txt

A

10
40

B

apple
apple

C

20
30

D

10
20
30
40

💡 Hint

Look for lines where the first word is 'apple' and print the second word.

The pattern '$1 == "apple"' selects lines where the first field is 'apple'. The action prints the second field, which are 10 and 40.

💻 Command Output

intermediate

What does this awk script print?

Consider the file numbers.txt with content:

5
10
15
20
25

What is the output of:

awk '{if ($1 > 15) print $1 * 2; else print $1}' numbers.txt

A

5
10
15
80
100

B

10
20
30
40
50

C

5
10
15
20
25

D

5
10
15
40
50

💡 Hint

Check which numbers are greater than 15 and double them.

Numbers greater than 15 (20 and 25) are doubled (40 and 50). Others print as is.

📝 Syntax

advanced

Which awk command correctly prints the second field only for lines where the first field starts with 'a'?

Choose the correct awk command to print the second field only if the first field starts with the letter 'a'.

A awk '$1 =~ /^a/ {print $2}' file.txt

B awk '$1 == /^a/ {print $2}' file.txt

C awk '$1 ~ /^a/ {print $2}' file.txt

D awk '$1 = /^a/ {print $2}' file.txt

💡 Hint

Use the correct operator for regex matching in awk.

The operator '~' is used for regex matching. '$1 ~ /^a/' matches lines where first field starts with 'a'.

💻 Command Output

advanced

What is the output of this awk script with multiple actions?

Given items.txt content:

pen 5
pencil 3
eraser 2
pen 7

What does this command print?

awk '$1 == "pen" {sum += $2} END {print sum}' items.txt

A 12

B

5
7

C penpen

D 0

💡 Hint

Sum the second field values only for lines where first field is 'pen'.

The script sums 5 and 7 from lines with 'pen' and prints 12 at the end.

🚀 Application

expert

How many lines does this awk command print?

Given log.txt with:

error 404
info start
error 500
warning low
error 404

How many lines will this command print?

awk '/error/ && $2 == 404' log.txt

A 3

B 2

C 1

D 0

💡 Hint

Count lines containing 'error' and second field equals 404.

Lines 1 and 5 match both conditions, so 2 lines are printed.