This is a text-only version of the following page on https://raymii.org: --- Title : Exclude lines in less (or journalctl) Author : Remy van Elst Date : 23-05-2021 URL : https://raymii.org/s/snippets/Exclude_lines_in_less_or_journalctl.html Format : Markdown/HTML --- This is a small tip I want to give you when using a `less` based pager, for example in `journalctl` or when viewing a file interactively with `less` or `more`. You can exclude certain lines that match one or multiple words (or a regex) with a few keystrokes, once `less` is open. This is one of those tips you never knew you needed, but when you know it, you'll use it frequently. Like in my case today when searching through some logfiles to find out why my database stopped working.

Recently I removed all Google Ads from this site due to their invasive tracking, as well as Google Analytics. Please, if you found this content useful, consider a small donation using any of the options below. It means the world to me if you show your appreciation and you'll help pay the server costs:

GitHub Sponsorship

PCBWay referral link (You get $5, I get $20 after you've placed an order)

Digital Ocea referral link ($200 credit for 60 days. Spend $25 after your credit expires and I'll get $25!)

Once your file is open in `less` (or `journalctl`) press the following keys: - `&` (ampersand, capital 7) - `!` (exclamation mark, capital 1) - `your-exclude-keyword` Ampersand opens the pattern matching mode, exclamation mark tells `less` to exclude the following part, and then you enter your search term. Here is a picture showing it in action: ![gif of exclude in less][1] ([Here's a guide][3] how to make such screen recordings with ffmpeg.) To make this even more useful, if you have presses `&!`. you can press `UP` to get your last command. Want to exclude another word? Just add a pipe to it. Example to exclude both `cron` and `sshd`: &!cron|sshd As these are just simple regexes, imagine the rest you can do. More information can be found in the [manpage][4] of `less`: &pattern Display only lines which match the pattern; lines which do not match the pattern are not displayed. If pattern is empty (if you type & immediately followed by ENTER), any filtering is turned off, and all lines are displayed. While filtering is in effect, an ampersand is displayed at the beginning of the prompt, as a reminder that some lines in the file may be hidden. Certain characters are special as in the / command+: ^N or ! Display only lines which do NOT match the pattern. The pattern is a regular expression, as recognized by the regular expression library supplied by your system. I was troubleshooting why my RSS reader ([miniflux][2]) stopped working, it gave an error telling me it couldn't connect to the database. Turns out the [VPS][99] had run out of memory a day earlier and the database was hit by the out-of-memory (OOM) killer. By excluding all irrelevant stuff I was able to figure out really quickly what the actual error was: May 23 03:00:49 s1 kernel: Out of memory: Kill process 18545 (postgres) score 140 or sacrifice child May 23 03:00:49 s1 kernel: Killed process 18545 (postgres) total-vm:320656kB, anon-rss:2068kB, file-rss:1088kB, shmem-rss:137824kB May 23 03:00:49 s1 kernel: oom_reaper: reaped process 18545 (postgres), now anon-rss:0kB, file-rss:0kB, shmem-rss:137824kB May 23 03:00:49 s1 kernel: python invoked oom-killer: gfp_mask=0x14200ca(GFP_HIGHUSER_MOVABLE), nodemask=(null), order=0, oom_score_adj=0 Earlier on in the log I could find out which process was the culprit to actually invoke the OOM killer, that has been resolved with some config file tweaking. [1]: /s/inc/img/lessclude.gif [2]: https://miniflux.app/ [3]: /s/snippets/Record_your_Linux_Desktop_with_ffmpeg_and_slop.html [4]: http://manpages.ubuntu.com/manpages/focal/en/man1/less.1.html [99]: https://www.digitalocean.com/?refcode=7435ae6b8212 --- License: All the text on this website is free as in freedom unless stated otherwise. This means you can use it in any way you want, you can copy it, change it the way you like and republish it, as long as you release the (modified) content under the same license to give others the same freedoms you've got and place my name and a link to this site with the article as source. This site uses Google Analytics for statistics and Google Adwords for advertisements. You are tracked and Google knows everything about you. Use an adblocker like ublock-origin if you don't want it. All the code on this website is licensed under the GNU GPL v3 license unless already licensed under a license which does not allows this form of licensing or if another license is stated on that page / in that software: This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see . Just to be clear, the information on this website is for meant for educational purposes and you use it at your own risk. I do not take responsibility if you screw something up. Use common sense, do not 'rm -rf /' as root for example. If you have any questions then do not hesitate to contact me. See https://raymii.org/s/static/About.html for details.