Regex Specify space or start of string and space or end of string

Question

Imagine you are trying to pattern match  stackoverflow    You want the following    this is stackoverflow and it rocks  MATCH    stackoverflow is the best  MATCH    i love stackoverflow  MATCH    typostackoverflow rules  NO MATCH    i love stackoverflowtypo  NO MATCH    I know how to parse out stackoverflow if it has spaces on both sites using     s stackoverflow  s    Same with if its at the start or end of a string      stackoverflow  s     s stackoverflow      But how do you specify  space or end of string  and  space or start of string  using a regular expression

User · Answer

Here s what I would use       lt   S stackoverflow    S    In other words  match  stackoverflow  if it s not preceded by a non-whitespace character and not followed by a non-whitespace character   This is neater  IMO  than the  space-or-anchor  approach  and it doesn t assume the string starts and ends with word characters like the  b approach does

User · Answer

You can use any of the following    b       A word break and will work for both spaces and end of lines      s    the   means or     is a capturing group       b stackoverflow  b    Also  if you don t want to include the space in your match  you can use lookbehind aheads      lt   s             to look behind the match  stackoverflow     the string you want     optional     s              to look ahead

User · Answer

b matches at word boundaries  without actually matching any characters   so the following should do what you want    bstackoverflow b

User · Answer

s  would match space or start of string and     s  for space or end of string  Together it s       s stackoverflow    s

[regex] Regex: Specify "space or start of string" and "space or end of string"

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