Further Reading

• man grep and info grep and man rg
  • At least go through all options ;)
  • Usage section in info grep has good examples as well
• A bit of history
  • Brian Kernighan remembers the origins of grep
  • How grep command was born
  • Why GNU grep is fast
• Q&A on stackoverflow/stackexchange are good source of learning material, good for practice exercises as well
  • grep Q&A on stackoverflow
  • grep Q&A on unix stackexchange
• Learn Regular Expressions (has information on flavors other than BRE/ERE/PCRE too)
  • regular-expressions — tutorials and tools
  • rexegg — tutorials, tricks and more
  • stackoverflow: What does this regex mean?
  • online regex tester and debugger — by default pcre flavor
• My ebooks on CLI text processing tools

Here are resource links for specific topics:

• ASCII reference and locale usage
  • ASCII code table
  • wiki.archlinux: locale
  • shellhacks: Define Locale and Language Settings
  • unix.stackexchange: What does LC_ALL=C do?
• unix.stackexchange: When to use grep, sed, awk, perl, etc
• stackoverflow: Grep output with multiple Colors
• unix.stackexchange: Multicolored Grep
• unix.stackexchange: grep -r vs find+grep
• unix.stackexchange: Counting the number of lines having a number > 100

Happy learning and please do let me know your feedback :)