How to check if a line is blank using regex

Question

I am trying to make simple regex that will check if a line is blank or not   Case        some       not blank         blank       blank

User · Answer

Here Blank mean what you are meaning  A line contains full of whitespaces or a line contains nothing  If you want to match a line which contains nothing then use

User · Answer

The pattern you want is something like this in multiline mode     s     Explanation      is the beginning of string anchor    is the end of string anchor   s is the whitespace character class    is zero-or-more repetition of    In multiline mode    and   also match the beginning and end of the line   References    regular-expressions info Anchors  Character Classes  and Repetition      A non-regex alternative   You can also check if a given string line is  blank   i e  containing only whitespaces  by trim  -ing it  then checking if the resulting string isEmpty     In Java  this would be something like this   if  line trim   isEmpty             line is  blank      The regex solution can also be simplified without anchors  because of how matches is defined in Java  as follows   if  line matches    s              line is  blank      API references   String String trim     Returns a copy of the string  with leading and trailing whitespace omitted   boolean String isEmpty     Returns true if  and only if  length   is 0    boolean String matches String regex    Tells whether or not this  entire  string matches the given regular expression

User · Answer

The most portable regex would be     t n    to match an empty string  note that you would need to replace  t and  n with tab and newline accordingly  and     n t  to match a non-whitespace string

User · Answer

Full credit to bchr02  for this answer  However  I had to modify it a bit to catch the scenario for lines that have     end of comment  followed by an empty line  The regex was matching the non empty line with      New       r n  n  r        r n  n  r     s   gm  All I did is add   as second character to signify the start of line

User · Answer

Well   I tinkered around  using notepadd    and this is the solution I found   n s   n for end of line  where you start matching  -- the caret would not be of help in my case as the beginning of the row is a string   s takes any space till the next string  hope it helps

User · Answer

Actually in multiline mode a more correct answer is this       r n  n  r        r n  n  r     s   gm   The accepted answer    s   does not match a scenario when the last line is blank  in multiline mode

User · Answer

Try this     s

[regex] How to check if a line is blank using regex

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