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

If you’re like me; you like files, you like web technologies like HTML, CSS, and JavaScript, you like markdown, you like kanban, you like pomodoro, and you like apps. If this sounds like you reach out. I’ll be open sourcing something in the coming weeks a…

via Colin Devroe September 3, 2025

Pluralistic: The worst possible antitrust outcome (03 Sep 2025)

Today's links The worst possible antitrust outcome: Hope you like enshittification. Hey look at this: Delights to delectate. Object permanence: Amazon drivers hang phones from trees; DVD Jon v Windows DRM; Chevron's dirty tricks. Upcoming appearan…

via Pluralistic: Daily links from Cory Doctorow September 3, 2025

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 3, 2025

Generated by openring