Regular Expression to Match Non-Whitespace Characters

Question

I need to make a regular expression that matches something like:

JG2144-141/hello

or

but not:

laptop bag

or a string consisting of whitespace chars only (' ').

Right now I have [A-Za-z0-9-!/\S], but it isn't working because it still matches with laptop and bag individually. It shouldn't match laptop bag and the empty string at all.

Wiktor Stribiżew · Answer 1 · 2022-02-16T22:18:11.247

12

In general, to match any non-whitespace char, you can use

\S              # Common modern regex flavors
[^[:space:]]    # POSIX compliant
[[:^space:]]    # POSIX extension (available in some flavors)
%S              # Lua patterns

The \S in [A-Za-z0-9-!/\S] makes this character class equal to \S, but you want to make sure all chars in the string are non-whitespace chars. That is why you should wrap the pattern with ^ and $ anchors and add a + quantifier after \S to match 1 or more occurrences of this subpattern.

You may use

^\S+$

See the regex demo

Details

^ - start of string
\S+ - 1 or more non-whitespace chars
$ - end of string.

edited Feb 16 '22 at 22:18

answered Nov 19 '17 at 21:18

Wiktor Stribiżew

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Okay that makes sense, thank you. What would I do if I wanted to allow a space at the beginning of the word? For example: """ JG2144-141/hello ! """ – Jennifer Hall Nov 19 '17 at 21:38
@JenniferHall: If you mean you want to match leading/trailing 0+ whitespaces, `^\s*\S+\s*$`. Or to match any non-word chars: `^\W*\S+\W*$` or `^\s*\S+\W*$` – Wiktor Stribiżew Nov 19 '17 at 21:39
No I meant it should match even if there is a space before. Like if you put the words in a triple quote """ and have JG2144-141/hello on the next line after the """, it won't match unless it is on the same line as the """. – Jennifer Hall Nov 19 '17 at 21:42
@JenniferHall Please formulate the rules as your examples are not helpful enough to deduce those rules. – Wiktor Stribiżew Nov 19 '17 at 21:43
@JenniferHall Sorry, that does not make sense. Are you trying to parse Python code? – Wiktor Stribiżew Nov 19 '17 at 21:49
Sort of, I was given these words and told to match one or more non-whitespace characters – Jennifer Hall Nov 19 '17 at 21:50
@JenniferHall Again, please formulate the rules. `JG2144-141/hello ! hi there` should not match as per the original post. – Wiktor Stribiżew Nov 19 '17 at 21:52
Sorry, ignore the original post, the words are meant to be put together like you just said. And only JG2144-141/hello and ! are supposed to match. Sorry about the confusion – Jennifer Hall Nov 19 '17 at 21:56
@JenniferHall No idea what you are doing. [`(?sm)^"""(.*?)"""$`](https://regex101.com/r/c38XMQ/4)? – Wiktor Stribiżew Nov 19 '17 at 21:58
@JenniferHall Did that finally work for you? – Wiktor Stribiżew Apr 21 '21 at 08:06

Regular Expression to Match Non-Whitespace Characters

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