regular expression for anything but an empty string

Question

Is it possible to use a regular expression to detect anything that is NOT an  empty string  like this   string s1       string s2        string s3         string s4            etc   I know I could use trim etc  but I would like to use a regular expression

User · Answer

Assertions are not necessary for this    S should work by itself as it matches any non-whitespace

User · Answer

Create  regular expression to detect empty string   and then inverse it  Invesion of regular language is the regular language  I think regular expression library in what you leverage - should support it  but if not you always can write your own library      grep --invert-match

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What about       S      This means      delimiter      zero or more of anything but newline  S   anything except a whitespace  newline  tab  space     so you get match anything but newline   something not whitespace   anything but newline

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We can also use space in a char class  in an expression similar to one of these               S               S 1            0      S 1            0 1     S 1      depending on the language flavor that we might use    RegEx Demo  Test  using System  using System Text RegularExpressions   public class Example       public static void Main                 string pattern                 S             string input                   abcd             ABCD1234                  amp                      abc def             ABC 123                        RegexOptions options   RegexOptions Multiline           foreach  Match m in Regex Matches input  pattern  options                         Console WriteLine    0   found at index  1     m Value  m Index                       C  Demo    If you wish to simplify modify explore the expression  it s been explained on the top right panel of regex101 com  If you d like  you can also watch in this link  how it would match against some sample inputs     RegEx Circuit  jex im visualizes regular expressions

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You can do one of two things    match against   s    a match means the string is  empty         are the beginning and end of string anchors respectively  s is a whitespace character   is zero-or-more repetition of  find a  S  an occurrence means the string is NOT  empty     S is the negated version of  s  note the case difference   S therefore matches any non-whitespace character    References   regular-expressions info  Anchors  Repetition MSDN - Character classes - Whitespace character  s   Note that unless you re using RegexOptions ECMAScript   s matches things like ellipsis        Related questions    Net regex  what is the word character  w

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You could also use   public static bool IsWhiteSpace string s         return s Trim   Length    0

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In  Net 4 0  you can also call String IsNullOrWhitespace

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s        will match any string that contains at least one non-space character   So  if  Regex IsMatch subjectString         s                  Successful match   else          Match attempt failed     should do this for you     anchors the search at the start of the string       s     a so-called negative lookahead  asserts that it s impossible to match only whitespace characters until the end of the string      will then actually do the match  It will match anything  except newline  up to the end of the string  If you want to allow newlines  you ll have to set the RegexOptions Singleline option     Left over from the previous version of your question     s     matches strings that contain only whitespace  or are empty    The exact opposite     S     matches only strings that consist of only non-whitespace characters  one character minimum

User · Answer

I think     4  might work in the example where you need to detect 4 spaces  Same with the rest      1       2  and     3   If you want to detect an empty string in general         will do

[c#] regular expression for anything but an empty string

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