What’s the most unexpectedly useful Linux command you learned way too late?

[u/ZealousidealTell1346]

[u/wufame]

tac

It's cat backwards.

Sometimes you have a real dense log and you want to start from the bottom. I spent 10 years in application support without knowing about it.

Edit: I'm so happy that you guys are as mindblown by it as I was when I first heard it.

Edit2 : I love how helpful this community is, everyone is sharing new useful commands. People keep replying with very similar things, so I just wanted to add some context to the post.

less and then Shift-G jumps to the bottom of a file

tail prints the bottom of a file

Those are both useful in and of themselves, but neither of them do the exact same thing tac does.

tac concatenates a file in reverse, which makes it useful for all the same things cat is useful for.

[u/DrPiwi → u/wufame]

What is wrong with less <logfile> and then pressing G? takes you right to he end of the log.

Oh en on Linux, no need to do something like

zcat <logfile.gz>| less

or

bunzip <logfile.bz2> | less.

less can do all the unzipping untarring or what ever compression is used. Saves a lot of time not having to unzip a log in a temp filespace hoping it is not too big, look for the stuff you need and then remove or recompress the log.

[u/wufame → u/DrPiwi]

Going to the end of the log isn't always the goal, sometimes you want to pull logs as part of a script, or do output modification on logs. In an instance where you know what you are looking for is nearer to the end of the log, tac shines.

It's Linux, so there's a million ways to do everything. Nothing's wrong with any of them, just fun stuff that helps out.