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Comment by latexr | Hacker News Reader

While I agree with the larger sentiment I think you’re making (I also make it a habit to peruse the manual just to see what is available), how often do you reread the manual, especially for your shell? I knew about associative arrays in bash, but not by reading the manual as those were introduced in v4 and I’ve been using bash for longer than that.

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You should probably read the release notes for new major versions. Also, anytime you think “I wish there was <feature> available in this program”, you should probably double-check if such a feature has appeared since you last learned the program.

That's how I discovered the '&' regex feature in less some years back.

Do you mean PCRE’s “(?&name)” feature? That is not portable; for instance, Python calls it “(?P=name)”. Or do you mean the common feature of “&” in the replacement string meaning “the whole matched string”? While this feature is common in languages which use regexps (including ed, sed, awk, etc.), that’s not actually a regexp feature, since the & character has that effect in the replacement string, not in the regular expression. It is also not always portable; for instance, Emacs requires escaping as \& for the character to have the special feature.

From man(1) 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.

  $ less --version
  less 487 (GNU regular expressions)
  Copyright (C) 1984-2016  Mark Nudelman

Oh, you meant the program “less”! Right, I understand what you meant now.

:-)

Yeah.

I was viewing some files and thinking "it'd be really cool if less(1) had some way of filtering to just lines matching a specific pattern".

RTFM'd and TIL'd.

Mind that at that point I'd used less for ... oh, at least 30 years.

Agreed. This is also how I found out that features in Python I took for granted, like breakpoint(), were much more recent than I thought (3.7). Nothing like having to use ancient versions of a language to discover limitations.

I do a fair bit of bash scripting and there is no way I can remember all the features and syntax I use, so of course I read parts of the manual regularly and often learn new things. You don't need to ever read the whole thing.

I once worked with a dev (frontend, of all things) who reread the bash manual annually.

I work in ops, and I don’t even have that dedication. My hat is off to them.

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