mapdirective
Matthias SchmidtWow, after 25 years of Unix experience, I learned that you can filter output in #less.
Press ampersand (&) and enter a regex to show only lines matching the regex.
Press ampersand (&) and then exclamation mark (!) to apply an inverse filter.
Wolf480pl@_xhr_ I ususally use grep to filter text streams, but when I don't, it's because I want to see the surrounding non-matching lines, so slash search (/) in less is much more useful to me
AndreasEK@wolf480pl @_xhr_ I think it was the '-C n' parameter that told grep to output n lines before and after a match
@AndreasEK @_xhr_ yes, but that requires knowing ahead if time how many lines you need. Which you usually don't know when looking through logs for a problrm that you're seeing for the first time.
okanogen VerminEnemyFromWithin@wolf480pl @_xhr_
I'm a fan of "tail -n x | head -n y" when stepping through logs and grep -C x if I have an idea what I need, but this less command looks interesting. Maybe pipe it after the first piped command! Go crazy!
I'm a fan of "tail -n x | head -n y" when stepping through logs and grep -C x if I have an idea what I need, but this less command looks interesting. Maybe pipe it after the first piped command! Go crazy!
🇺🇦🇪🇺 cweickhmann@wolf480pl For grep, consider using the -C switch (context):
-C NUM, -NUM, --context=NUMPrint NUM lines of output context. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given.@xhr@cybervillains.com
@cweickhmann @_xhr_ yeah I know how -C works, and I use it when it makes sense. But it only works when you know ahead of time how much context you need. I think I already said that somewhere else in the thread but can't find it now because mastodon likes to forget about old posts...
@wolf480pl
Absolutely. (Honestly, I didn’t check if you mentioned it elsewhere. I just thought in that context it may be useful for you or someone else reading the thread 😉)
@xhr@cybervillains.com
Absolutely. (Honestly, I didn’t check if you mentioned it elsewhere. I just thought in that context it may be useful for you or someone else reading the thread 😉)
@xhr@cybervillains.com
Pete@_xhr_ that’s amazing! (Also amazing: watching other people use almost entirely different subsets of vi commands at speed to my own)
halfur@_xhr_ Oh that is fantastic! Do you by any chance know which flavor of regex it uses? POSIX?
MikeK
D2@mkarliner @_xhr_ (fellow more-ingrained nerds, Unite!!)
Lars Karlslund 
Also:
/ = search forward
? = search backward
Didn't know the & trick TBH, good one :-)
Gustav H Meyer@[email protected] wow, I never noticed this, and it is even documented. Nice! 😎
KasTas@_xhr_ woaaaaa, and it does chain!
No more daisy chains of greps, pipes and less at the end o_0
Bunch of future life-years of piping and greping reclaimed for other uses!
Thanks!
Kou Ki@KasTasMykolas what do u mean "it does chain"? @_xhr_
Wilfried Klaebe@KasTasMykolas Is there a way to undo them? The last one, single ones, or at least all of them?
Andy Smith@_xhr_ I only learned this in the last two years or so as well. Linux user since 1995.
@_xhr_ by the way, for Your defence, it may be not so old addition. For now I can find it crawling into FreeBSD codebase somewhere between 7.3.0 and 7.40:
https://github.com/dspinellis/unix-history-repo/blob/FreeBSD-release/7.4.0/contrib/less/less.man#L260-L274
So, at least 10-11 years ago.
edythemighty@_xhr_ ok that's a new one for me too
Carlos 🐧
Daniel Gibson@_xhr_ TIL!
BTW, another neat function (at least in the GNU version?) is pressing Shift-F to make it follow the file (scroll to the end and update when the file changes) - useful for logs!
OliverUv
Moss@OliverUv @Doomed_Daniel Life changing!
moontarantula@Doomed_Daniel @_xhr_ this is incredibly useful
ziisch@Doomed_Daniel @_xhr_ You can also do cat | less +F to follow line immediately. Useful for repeated commands
Christian Saris
IPng Networks@_xhr_ another day another "TIL" 🙂
Joe Cotellese@_xhr_ I've been doing cat | grep | less for years. This is way better.
Mark Derricutt (talios)@JoeCotellese @_xhr_ I find it more “cat | grep | grep | grep | grep | grep | less” for me - sometimes I need multiple layers of filtering as I’m trying to find for specific data.
Stephen Foskett
Neil Hanlon@_xhr_ wait what
Iñigo Serna 
@_xhr_ Ein???
Same here.
Same here.
morph@_xhr_ I feel like I’ve read this exact toot months ago 🤔
Mark Gardner@_xhr_ I've taken to using @siegel's #BBEdit to opening and receiving pipelines on #macOS. It has nice command line tools to spawn windows for diffing, tailing log files, and parsing results. And its search capabilities are unmatched. https://www.barebones.com/products/bbedit/featuresadmin.html
Christopher Pickslay@mjgardner @_xhr_ @siegel oh this is nice. I can’t count the number of times I’ve copied terminal output into a file in BBEdit to search it.
wimletzer ✅@_xhr_ Well, I was never any good at regex. But my unix experience is even larger than yours ( 30+ years ), and I am still learning new features.
You S Blues@wimletzer @_xhr_ Same. I tell myself that it’s my ninja like vi macro skills that took up the space where regex-off-the-cuff would go.
Joost@_xhr_ wow, new to me also. So less is more. More than needed though, the & thingy is against Unix philosophy; there is grep before less. I've given the fact that a pager can go back a lot of thought before deciding its not totally against Unix philosophy.
ikari
Lars Marowsky-Brée 😷
Adam Spiers 🇪🇺🇬🇧🇮🇪🦇🔊@_xhr_ This is super cool (and I'm embarrassed I didn't know it) ... BUT https://lnav.org/ basically makes #less obsolete - it's a superb tool which I strongly recommend to all #less users. Check out the features page!
Dan, D-List Super Villain@_xhr_ greetings fellow Villain. In my experience RegEx is both the solution that keeps on giving, and the one that robs me of the most sleep. It’s a double edged sword, and I wouldn’t have it any other way.
Tommy Þ@_xhr_ 30+ years here and I didn’t know that, but I’m used now to there being an abundance of features in my tools for me to discover. I expect never to fully know what Emacs can do.
gnarf@tommythorn
I decided to play on Emacs like on an instrument instead of using it. Feels better now. :)
@_xhr_
I decided to play on Emacs like on an instrument instead of using it. Feels better now. :)
@_xhr_
Nico -telmich- Schottelius@_xhr_ That's a lot more than you expect from less.
yetzt@_xhr_ psst! this is only revealed after someone has done 50 years of unix.
arensb
Charles Fulton@_xhr_ My God.
Daniel Gordon
Jeff Caughel
Ryan Steele 
Tom von Alten@_xhr_ Instafollow for combining less and regex 😃 (even though I never did use less that much, in... 35 years, hardly seems real to say)
Scott 🏳️⚧️🏳️🌈🇵🇸🇨🇺@_xhr_ I needed this in my life. Thank you!
Tinyrabbit ✅@_xhr_ TIL :) And I've been a sysadmin for "only" 12 years. Thanks!
Le Chep
EyalLIt's incredibly slow unfortunately :(
I use https://github.com/tigrawap/slit/releases as a much nicer less alternative, with many more features:
See its readme: https://github.com/tigrawap/slit#readme
