awk basics (field processing) in Linux CLI - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does awk do in simple terms?

awk is a tool that reads text line by line and splits each line into parts called fields. It helps you pick and work with these parts easily.

beginner

In awk, how do you refer to the first field of a line?

You use $1 to get the first field (like the first word) in the current line.

beginner

What does $0 represent in awk?

$0 means the whole current line as it is, without splitting.

beginner

How can you print the second and third fields of each line using awk?

Use awk '{print $2, $3}' filename. This prints the second and third parts of each line separated by space.

beginner

What is the default field separator in awk?

The default separator is any space or tab. awk splits lines by spaces or tabs unless told otherwise.

What does $3 represent in an awk command?

A The third field of the current line

B The whole line

C The third line of the file

D The number of fields in the line

$3 is the third field (word or part) in the current line processed by awk.

Which awk variable holds the entire current line?

A NR

B $1

C FS

D $0

$0 contains the full current line in awk.

How does awk split fields by default?

A By spaces or tabs

B By commas

C By semicolons

D By new lines

By default, awk splits fields using spaces or tabs.

What command prints the first and last fields of each line using awk?

A awk '{print NF}' filename

B awk '{print $0}' filename

C awk '{print $1, $NF}' filename

D awk '{print $2, $3}' filename

$1 is the first field, $NF is the last field in awk.

If a line has 5 fields, what does NF equal in awk?

A 4

B 5

C 1

D 0

NF is a built-in variable that holds the number of fields in the current line.

Explain how awk processes a line and how you can access its parts.

Think about how a sentence breaks into words.

Describe how to print specific fields from a file using awk.

Imagine picking certain words from each line.