Knowledge Base (Posts about regex)

Updating my cgit links for Luanti projects

bgstack15 — Wed, 09 Apr 2025 13:11:00 GMT

I decided that my thousands of Luanti-related repositories should be stored in their own special spot, er, heading in my cgit, visible in the whole list only on the last page. I guess I can't link directly to just the heading in the whole list cgit, but at least you can view only those repos if desired with the first link.

To adjust my recent blog posts that pointed to the old locations, I had to use some regex.

vi $( grep -l -rI -P '(?<=\(\/cgit\/)[^\)]+' posts/2025 )

This found any link that starts with /cgit/ so I can go edit it.

References

Weblinks

Regex Tutorial - Lookahead and Lookbehind Zero-Length Assertions

vim set regextype perl

bgstack15 — Fri, 07 Apr 2017 13:48:18 GMT

The problem

Vim is a great editor. I use it every day, and that includes weekends. I've run into an issue where to search with the regular expression (dest|path): I needed to escape the parentheses and the pipe. That gets tedious.

The solution

I found my solution at stackoverflow: http://stackoverflow.com/questions/5770058/vim-and-regular-expression-what- kind-of-regex-does-vim- use/26600989#26600989. At the beginning of your search expression, use \v which then uses a "very magic" regex mode in which fewer escapes are needed. /\v(dest|path):

Hide comments and blank lines in file

bgstack15 — Fri, 24 Jun 2016 18:37:35 GMT

Hide comments and blank lines when viewing file

Original title: Show all non-blank non-comment lines in file

If you want to see just the lines with content, such as in a config file, use this one-liner:

grep -viE '^\s*((#|;).*)?$' smb.conf

How it works

grep -v means invert the selection, i.e., everything that does not match this search. -iE case Insensitive, and treat this as a regular Expression. Technically there are no letters being searched, so the i is irrelevant, but I always use it in my searches anyway. ^ start of line \s white space, any amount from zero onward. This is a greedy search, so it will match all the white space (spaces, tabs, etc.) (#|;) either a pound or a semicolon, which usually denote comments in config files (in my case, smb.conf) ((#|;).) the above sentence, followed by any character (the period), and any amount of those "any characters." ((#|;).)? the whole thing in parentheses shown here, optionally. $* end of line So any line that starts with any amount of white space, followed by (a comment symbol, followed by anything else) optionally, and the end of the line. So show everything but the above sentence, and tada, just the important stuff.