What is NF used for in awk?

In awk, NF stands for Number of Fields. It represents the total number of columns (fields) in the current line being processed.

Here are the most common ways to use NF:

1. Accessing the Last Column

Since NF is the total count of fields, $NF (with a dollar sign) refers to the value of the very last field, regardless of how many columns are in the line.

# Prints the last column of every line
awk '{print $NF}' awk_test.txt

2. Filtering by Column Count

You can use NF to find lines that have a specific number of data points. For example, to find lines that are missing data:

# Only prints lines that have exactly 3 columns
awk 'NF == 3' awk_test.txt

3. Processing Variable Data

If you have a file where some lines have more words than others, NF helps you handle them dynamically.

# Prints how many words (fields) are on each line
awk '{print "Line " NR " has " NF " fields"}' awk_test.txt

Summary of the difference:

• NR: Number of Records (the current Row number).
• NF: Number of Fields (the count of Columns in the current row).
• $NF: The content of the last column.

Would you like to try running a command using NF on your awk_test.txt to see how it works?