How to check if a line is blank using regex
RegexRegex Problem Overview
I am trying to make simple regex that will check if a line is blank or not.
Case;
" some" // not blank
" " //blank
"" // blank
Regex Solutions
Solution 1 - Regex
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:
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()
is0
.
- Returns
boolean String.matches(String regex)
- Tells whether or not this (entire) string matches the given regular expression.
Solution 2 - Regex
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).
Solution 3 - Regex
Try this:
^\s*$
Solution 4 - Regex
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.
Solution 5 - Regex
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.
Solution 6 - Regex
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 '/^$/'.
Solution 7 - Regex
This regex will delete all empty spaces (blank) and empty lines and empty tabs from file
\n\s*
Solution 8 - Regex
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