Reading gz files with zcat

| linux | tui |

The Debian Policy Manual dictates that all packages should come with documentation. In order to save space in the debian archive these documents need to be compressed with gzip. There are a ton of these files floating around in the /usr/share/doc directory. Recently I wanted to read some of the documentation. If you try to open the file with cat it spits out binary gibberish. You can of course unzip the file as you normally would and open it up that way, but it turns out there is an easier way. Using zcat you can read the contents of compressed files just like you would with cat.

zcat is identical to gunzip -c. (On some systems, zcat may be installed as gzcat to preserve the original link to compress.) zcat uncompresses either a list of files on the command line or its standard input and writes the uncompressed data on standard output. zcat will uncompress files that have the correct magic number whether they have a .gz suffix or not. GZIP(1) man page.
By default, this will put all of the output into your terminal window, which is fine for most files. The other place where this can come in handy is when you are trying to look through compressed log files. In this case, having to scroll around the terminal may not be a great option. You can pipe the output of zcat into other programs such asless in order to be able to page through long files. For example, if I wanted to read the first 10 lines of a compressed log file, I could do so with the following command:
levlaz@debvm:/var/log$ sudo zcat syslog.2.gz | head -n 10
The output of this command would look like this:
May  2 22:27:43 debvm rsyslogd: [origin software="rsyslogd" swVersion="8.4.2" x-pid="585" x-info="https://www.rsyslog.com"] start
May  2 22:27:43 debvm kernel: [    0.000000] ACPI: LAPIC_NMI (acpi_id[0x1a] high edge lint[0x1])
May  2 22:27:43 debvm kernel: [    0.000000] ACPI: LAPIC_NMI (acpi_id[0x1b] high edge lint[0x1])
May  2 22:27:43 debvm kernel: [    0.000000] ACPI: LAPIC_NMI (acpi_id[0x1c] high edge lint[0x1])
May  2 22:27:43 debvm kernel: [    0.000000] ACPI: LAPIC_NMI (acpi_id[0x1d] high edge lint[0x1])
May  2 22:27:43 debvm kernel: [    0.000000] ACPI: LAPIC_NMI (acpi_id[0x1e] high edge lint[0x1])
May  2 22:27:43 debvm kernel: [    0.000000] ACPI: LAPIC_NMI (acpi_id[0x1f] high edge lint[0x1])
May  2 22:27:43 debvm kernel: [    0.000000] ACPI: LAPIC_NMI (acpi_id[0x20] high edge lint[0x1])
May  2 22:27:43 debvm kernel: [    0.000000] ACPI: LAPIC_NMI (acpi_id[0x21] high edge lint[0x1])
May  2 22:27:43 debvm kernel: [    0.000000] ACPI: LAPIC_NMI (acpi_id[0x22] high edge lint[0x1])

Thank you for reading! Share your thoughts with me on bluesky, mastodon, or via email.

Check out some more stuff to read down below.

Most popular posts this month

Recent Favorite Blog Posts

This is a collection of the last 8 posts that I bookmarked.

Articles from blogs I follow around the net

Give a Problem. Grow a Programmer.

In 2009, I kicked off my senior year in college with a class that ultimately changed the way I thought about my degree—and my future.

via flower.codes September 15, 2025

Yala stablecoin depegs after theft

The YU bitcoin-backed stablecoin list its intended dollar peg after what they described as "an attempted attack", later writing that there was an "unauthorized transfer of funds". Although they initially wrote that &#…

via Web3 is Going Just Great September 15, 2025

How big a solar battery do I need to store *all* my home's electricity?

I have a modest set of solar panels on an entirely ordinary house in suburban London. On average they generate about 3,800kWh per year. We also use about 3,800kWh of electricity each year. Obviously, we can't use all the power produced over summer an…

via Terence Eden’s Blog September 15, 2025

Generated by openring