4 ms·

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 p

by teddyh 2y ago

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.

dredmorbius 2y ago
That's how I discovered the '&' regex feature in less some years back.
- teddyh 2y ago
  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.
  - dredmorbius 2y ago
    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
    - teddyh 2y ago
      Oh, you meant the program “less”! Right, I understand what you meant now.
      - dredmorbius 2y ago
        :-) 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.
sgarland 2y ago
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.

by teddyh 2y ago

dredmorbius 2y ago

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

teddyh 2y ago
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.
- dredmorbius 2y ago
  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
  - teddyh 2y ago
    Oh, you meant the program “less”! Right, I understand what you meant now.
    - dredmorbius 2y ago
      :-) 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.

sgarland 2y ago

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.