Awk Fundamentals

Calculate useful totals from a small inventory file.

Use awk to work with columns, records, field separators, conditions, and totals.

Outcome: Tables and CSV-like files become approachable from the terminal.

Mental model

Understand what is happening

awk sees each line as a record and each column as a field.

$0 is the whole line; $1 is first field; NF is number of fields; NR is line number.

Guided lab

Work through the mission

Print fields

Safe

Prints columns and line numbers.

Terminal

cd ~/linux-practice
echo -e 'Name Age City\nJohn 30 NYC\nJane 25 LA' > data.txt
awk '{print $1, $3}' data.txt
awk '{print NR, $0}' data.txt

CSV separator

Safe

Uses comma as a field separator and calculates values.

Terminal

echo -e 'Product,Price,Quantity\nApple,1.50,100\nBanana,0.75,200' > inventory.csv
awk -F, 'NR>1 {print $1, $2 * $3}' inventory.csv

Total calculation

Safe

Accumulates a total and prints it at the end.

Terminal

awk -F, 'NR>1 {total += $2 * $3} END {print total}' inventory.csv

Checkpoint

Verify the mission

The calculated total matches the source data.

Try it yourself

One step without a recipe

Build a report from a small CSV: filter the rows you need, transform one value, calculate a total, and save the verified result without changing the source.

Need a hint?

When you're staring at a CSV or a table in the terminal, reach for awk. It turns messy text into columns you can actually work with. Start with `awk '{print $1}'` to see the first column, then build from there. It's the Swiss Army knife for structured text.

Explain it back

Before you move on

What does NR mean?
How do you set comma as the field separator?