Compare two CSV files and output only lines that differ

This guide shows you how to compare two CSV files and output the difference as a CSV file. As well as using HTMLTab it also uses sdiff, a standard tool on Linux and MacOS.

Let’s say that yesterday you requested data from https://example.com/data.csv and saved it to a local file named yesterday.csv.

htmltab https://example.com/data.csv > yesterday.csv

Today you can see the differences using:

htmltab https://example.com/data.csv > today.csv
sdiff --suppress-common-lines yesterday.csv today.csv

That will use HTMLTab to get the fresh CSV data from the URL, save it as today.csv, and use sdiff to compare the new data against the old, suppressing any lines that haven’t changed.

Tip

If you’re feeling adventurous, you can feed HTMLTab’s output directly into sdiff without saving an intermediate file:

sdiff --suppress-common-lines yesterday.csv <(htmltab https://example.com/data.csv)