regex.md

Regex

• Basic vs. Extended Regular Expressions:

  • In basic regular expressions these meta-characters lose their meaning: ? + { | ( )
  • instead use the backslashed versions: \? \+ \{ \| \( and \)
  • Grep manual
  • Open Group base specs:
  • Basic regular expressions (POSIX based) - why Vim has to escape brackets

• replace uppercase with lowercase

  • find all uppercase: ([A-Z])(.*)
  • L$1$2 --> will convert all letters in $1 and $2 to lowercase
  • l$1$2 --> will only convert the first letter of $1 to lowercase and leave everything else as is
  • The same goes for uppercase with U and u