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This post covers Basic Regular Expressions (BRE) and Extended Regular Expressions (ERE) syntax supported by GNU grep, sed and awk. You'll also learn the differences between these tools — for example, awk doesn't support backreferences within regexp definition (i.e. the search portion).

TL;DR: Small victories are more precious when you have nothing. Instead of burning through my savings, I'm now adding to it. The relief is priceless.

This post shows how you can use the ripgrep, perl and sd commands to perform multiline fixed string search and replace operations from the command line. Solutions with GNU sed is also discussed, along with its limitations.

This stackoverflow Q&A got me thinking about various ways to construct a solution in GNU sed if lookarounds are needed.

Only single line (with newline as the line separator) processing is presented here. Equivalent lookaround syntax with grep -P or perl is also shown for comparison. Cases where multiple lines and/or ASCII NUL characters are present in the pattern space is left as an exercise.

ripgrep (command name rg) is a grep tool, but supports search and replace as well. rg is far from a like-for-like alternate for sed, but it has nifty features like multiline replacement, fixed string matching, PCRE2 support, etc. This post gives an overview of syntax for substitution and highlights some of the cases where rg is a handy replacement for sed.

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Either you've already heard of pandoc or if you have searched online for markdown to pdf or similar, you are sure to come across pandoc. This tutorial will help you use pandoc to generate pdf and epub from a GitHub style markdown file. The main motivation for this blog post is to highlight what customizations I did to generate pdf and epub versions for self-publishing my ebooks. It wasn't easy to arrive at the setup I ended up with, so I hope this will be useful for those looking to use pandoc to generate pdf and epub formats. This guide is specifically aimed at technical books that has code snippets.

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Above diagram created using Regulex

Above visualization created using debuggex for the pattern r'\bpar(en|ro)?t\b'

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