带有空格的c样式字符串的regcomp表达式

Question

i am trying to detect an empty string or a string with just white spaces such as " ". It is ac application and uses regcomp and regexec .

For empty string "^$" works fine.

But for string with just whitespaces i am getting a problem. So far, i have come up with

"[\\\\s]*(?![A-za-z0-9])$"

Is there a better way to express it using perl style regular expression?

UPDATE: i actually changed it "[\\\\s]*(?![\\\\w\\\\d\\\\t\\\\n\\\\r]*)$"

The above gives an error when i give an input such as " m". The error is

"Invalid preceding regular expression"

Answer 1

To test string for only white spaces, its Reg-Ex will be...

^\\s*$

REF: helpful

How to test to see if a string is only whitespace in perl

Answer 2

You should use * or + quantifier..

So it should be ^\\s*$ or ^ *$

* matches 0 to many characters

+ matches 1 to many characters