Linux utils that you might not know

I was really happy about tac when I found out about it, same with paste and comm as already mentioned.

Gotten a lot of mileage out of the various seldom used options of uniq, diff and cut too.

It's to keep the page weight balanced. Prose is considered to have neutral buoyancy, but code is naturally heavier and will tend to drag the page down if that isn't compensated by a lighter font. FWIW poetry can be so light, that it can require a very heavy font weight to keep it tethered to the page.

That's not a great example as `pgrep` is a little more nuanced than running `ps [options] | grep [string]`, eg you cannot use many of the same `ps` flags `pgrep` like you can with `ps`.

At least with "in appropriate use of cat" (as some call it) you're literally just swapping the stdin file stream with a disk io file stream so there's no functional difference what-so-ever.

I'm not saying I agree with the GP either though as most of the time complaints about "in appropriate use of cat" are just showboating. Using `cat` "inappropriately" is arguably more readable for less seasoned shell script developer and it's certainly a more logical program flow for a human to parse. ie "open file, grep for contents, do something else, etc". But it's still sometimes worth a reminder that many string processing tools can accept file input directly without the need for piping it via stdin (or the files can be redirected directly from the shell via the less than, `<`, token).

No. Ext4 doesn't do data journaling by default. Even when enabled, what's written to the journal is blank data that's about to be written, not the current file's contents.

    1) write to journal "I'm going to overwrite this file with this data (zeros)"
    2) commit journal
    3) write data to file

This is typical for journaling filesystems-- step 3 can be interrupted by a crash and replayed later (by re-reading the journal).

For filesystems with CoW data (ZFS, btrfs), the in-place data will probably not be overwritten.

and iirc on SSDs you cant really a file with random bytes. Apple removed the "safe erasure" option from Finder because they couldn't guarantee deletion.