awk field extraction in scripts in Bash Scripting - 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 red
banana 5 yellow
cherry 20 red

What is the output of this command?

awk '{print $2}' data.txt

Bash Scripting

awk '{print $2}' data.txt

A

10
5
20

B

apple
banana
cherry

C

red
yellow
red

D

1
2
3

💡 Hint

Remember, awk fields are numbered starting from 1, and $2 means the second word in each line.

The command prints the second field ($2) from each line. The second words are 10, 5, and 20.

💻 Command Output

intermediate

Which awk command extracts the third field from a CSV file?

You have a CSV file records.csv with lines like:

John,Doe,30
Jane,Smith,25
Bob,Brown,40

Which command correctly prints the third field (age) from each line?

A awk -F':' '{print $3}' records.csv

B awk '{print $3}' records.csv

C awk -F',' '{print $2}' records.csv

D awk -F',' '{print $3}' records.csv

💡 Hint

CSV fields are separated by commas, so set the field separator to a comma.

Using -F',' sets the field separator to comma, so $3 is the third field (age).

📝 Syntax

advanced

Identify the syntax error in this awk script snippet

What is wrong with this awk command?

awk '{print $1 $2}' file.txt

It is intended to print the first and second fields separated by a space.

A Missing comma between $1 and $2 inside print

B No error, command is correct

C Incorrect use of single quotes

D Missing semicolon after print statement

💡 Hint

In awk, print $1 $2 prints the fields separated by the output field separator (OFS), which defaults to a single space.

There is no syntax error. The command correctly prints the first field, a space, and the second field using the default OFS.

🚀 Application

advanced

Extract and sum the second field values using awk

Given a file numbers.txt with lines:

a 3
b 7
c 10

Which awk command sums all values in the second field and prints the total?

A awk '{print sum + $2}' numbers.txt

B awk '{sum = $2} END {print sum}' numbers.txt

C awk '{sum += $2} END {print sum}' numbers.txt

D awk 'END {print sum}' numbers.txt

💡 Hint

Use a variable to accumulate the sum inside the main block, then print it in the END block.

Option C correctly adds each $2 to sum and prints sum after processing all lines.

🔧 Debug

expert

Why does this awk command fail to extract the fourth field?

You run this command:

awk '{print $4}' file.txt

But it prints empty lines even though the file has data.
The file lines look like:

one,two,three,four,five

What is the most likely reason?

A The file uses commas as separators but awk expects spaces by default

B The file uses tabs as separators but awk expects spaces by default

C The file lines have trailing spaces causing $4 to be empty

D The file uses multiple spaces or tabs, causing fields to be miscounted

💡 Hint

Check what character separates fields in the file and if awk is set to use it.

If fields are separated by commas, awk needs -F',' to split correctly. Without it, $4 is empty.