Regular Expression WhiteSpace Character that Excludes Newline [duplicate] - regex

Question

I sometimes want to match whitespace but not newline.
So far I've been resorting to [ \t]. Is there a less awkward way?

Answer 1

Use a double-negative:
/[^\S\r\n]/
That is, not-not-whitespace (the capital S complements) or not-carriage-return or not-newline. Distributing the outer not (i.e., the complementing ^ in the character class) with De Morgan's law, this is equivalent to “whitespace but not carriage return or newline.” Including both \r and \n in the pattern correctly handles all of Unix (LF), classic Mac OS (CR), and DOS-ish (CR LF) newline conventions.
No need to take my word for it:
#! /usr/bin/env perl
use strict;
use warnings;
use 5.005; # for qr//
my $ws_not_crlf = qr/[^\S\r\n]/;
for (' ', '\f', '\t', '\r', '\n') {
my $qq = qq["$_"];
printf "%-4s => %s\n", $qq,
(eval $qq) =~ $ws_not_crlf ? "match" : "no match";
}
Output:
" " => match
"\f" => match
"\t" => match
"\r" => no match
"\n" => no match
Note the exclusion of vertical tab, but this is addressed in v5.18.
Before objecting too harshly, the Perl documentation uses the same technique. A footnote in the “Whitespace” section of perlrecharclass reads
Prior to Perl v5.18, \s did not match the vertical tab. [^\S\cK] (obscurely) matches what \s traditionally did.
The same section of perlrecharclass also suggests other approaches that won’t offend language teachers’ opposition to double-negatives.
Outside locale and Unicode rules or when the /a switch is in effect, “\s matches [\t\n\f\r ] and, starting in Perl v5.18, the vertical tab, \cK.” Discard \r and \n to leave /[\t\f\cK ]/ for matching whitespace but not newline.
If your text is Unicode, use code similar to the sub below to construct a pattern from the table in the aforementioned documentation section.
sub ws_not_nl {
local($_) = <<'EOTable';
0x0009 CHARACTER TABULATION h s
0x000a LINE FEED (LF) vs
0x000b LINE TABULATION vs [1]
0x000c FORM FEED (FF) vs
0x000d CARRIAGE RETURN (CR) vs
0x0020 SPACE h s
0x0085 NEXT LINE (NEL) vs [2]
0x00a0 NO-BREAK SPACE h s [2]
0x1680 OGHAM SPACE MARK h s
0x2000 EN QUAD h s
0x2001 EM QUAD h s
0x2002 EN SPACE h s
0x2003 EM SPACE h s
0x2004 THREE-PER-EM SPACE h s
0x2005 FOUR-PER-EM SPACE h s
0x2006 SIX-PER-EM SPACE h s
0x2007 FIGURE SPACE h s
0x2008 PUNCTUATION SPACE h s
0x2009 THIN SPACE h s
0x200a HAIR SPACE h s
0x2028 LINE SEPARATOR vs
0x2029 PARAGRAPH SEPARATOR vs
0x202f NARROW NO-BREAK SPACE h s
0x205f MEDIUM MATHEMATICAL SPACE h s
0x3000 IDEOGRAPHIC SPACE h s
EOTable
my $class;
while (/^0x([0-9a-f]{4})\s+([A-Z\s]+)/mg) {
my($hex,$name) = ($1,$2);
next if $name =~ /\b(?:CR|NL|NEL|SEPARATOR)\b/;
$class .= "\\N{U+$hex}";
}
qr/[$class]/u;
}
Other Applications
The double-negative trick is also handy for matching alphabetic characters too. Remember that \w matches “word characters,” alphabetic characters and digits and underscore. We ugly-Americans sometimes want to write it as, say,
if (/[A-Za-z]+/) { ... }
but a double-negative character-class can respect the locale:
if (/[^\W\d_]+/) { ... }
Expressing “a word character but not digit or underscore” this way is a bit opaque. A POSIX character-class communicates the intent more directly
if (/[[:alpha:]]+/) { ... }
or with a Unicode property as szbalint suggested
if (/\p{Letter}+/) { ... }

Answer 2

Perl versions 5.10 and later support subsidiary vertical and horizontal character classes, \v and \h, as well as the generic whitespace character class \s
The cleanest solution is to use the horizontal whitespace character class \h. This will match tab and space from the ASCII set, non-breaking space from extended ASCII, or any of these Unicode characters
U+0009 CHARACTER TABULATION
U+0020 SPACE
U+00A0 NO-BREAK SPACE (not matched by \s)
U+1680 OGHAM SPACE MARK
U+2000 EN QUAD
U+2001 EM QUAD
U+2002 EN SPACE
U+2003 EM SPACE
U+2004 THREE-PER-EM SPACE
U+2005 FOUR-PER-EM SPACE
U+2006 SIX-PER-EM SPACE
U+2007 FIGURE SPACE
U+2008 PUNCTUATION SPACE
U+2009 THIN SPACE
U+200A HAIR SPACE
U+202F NARROW NO-BREAK SPACE
U+205F MEDIUM MATHEMATICAL SPACE
U+3000 IDEOGRAPHIC SPACE
The vertical space pattern \v is less useful, but matches these characters
U+000A LINE FEED
U+000B LINE TABULATION
U+000C FORM FEED
U+000D CARRIAGE RETURN
U+0085 NEXT LINE (not matched by \s)
U+2028 LINE SEPARATOR
U+2029 PARAGRAPH SEPARATOR
There are seven vertical whitespace characters which match \v and eighteen horizontal ones which match \h. \s matches twenty-three characters
All whitespace characters are either vertical or horizontal with no overlap, but they are not proper subsets because \h also matches U+00A0 NO-BREAK SPACE, and \v also matches U+0085 NEXT LINE, neither of which are matched by \s

Answer 3

A variation on Greg’s answer that includes carriage returns too:
/[^\S\r\n]/
This regex is safer than /[^\S\n]/ with no \r. My reasoning is that Windows uses \r\n for newlines, and Mac OS 9 used \r. You’re unlikely to find \r without \n nowadays, but if you do find it, it couldn’t mean anything but a newline. Thus, since \r can mean a newline, we should exclude it too.

Answer 4

The below regex would match white spaces but not of a new line character.
(?:(?!\n)\s)
DEMO
If you want to add carriage return also then add \r with the | operator inside the negative lookahead.
(?:(?![\n\r])\s)
DEMO
Add + after the non-capturing group to match one or more white spaces.
(?:(?![\n\r])\s)+
DEMO
I don't know why you people failed to mention the POSIX character class [[:blank:]] which matches any horizontal whitespaces (spaces and tabs). This POSIX chracter class would work on BRE(Basic REgular Expressions), ERE(Extended Regular Expression), PCRE(Perl Compatible Regular Expression).
DEMO

Answer 5

What you are looking for is the POSIX blank character class. In Perl it is referenced as:
[[:blank:]]
in Java (don't forget to enable UNICODE_CHARACTER_CLASS):
\p{Blank}
Compared to the similar \h, POSIX blank is supported by a few more regex engines (reference). A major benefit is that its definition is fixed in Annex C: Compatibility Properties of Unicode Regular Expressions and standard across all regex flavors that support Unicode. (In Perl, for example, \h chooses to additionally include the MONGOLIAN VOWEL SEPARATOR.) However, an argument in favor of \h is that it always detects Unicode characters (even if the engines don't agree on which), while POSIX character classes are often by default ASCII-only (as in Java).
But the problem is that even sticking to Unicode doesn't solve the issue 100%. Consider the following characters which are not considered whitespace in Unicode:
U+180E MONGOLIAN VOWEL SEPARATOR
U+200B ZERO WIDTH SPACE
U+200C ZERO WIDTH NON-JOINER
U+200D ZERO WIDTH JOINER
U+2060 WORD JOINER
U+FEFF ZERO WIDTH NON-BREAKING SPACE
Taken from https://en.wikipedia.org/wiki/White-space_character
The aforementioned Mongolian vowel separator isn't included for what is probably a good reason. It, along with 200C and 200D, occur within words (AFAIK), and therefore breaks the cardinal rule that all other whitespace obeys: you can tokenize with it. They're more like modifiers. However, ZERO WIDTH SPACE, WORD JOINER, and ZERO WIDTH NON-BREAKING SPACE (if it used as other than a byte-order mark) fit the whitespace rule in my book. Therefore, I include them in my horizontal whitespace character class.
In Java:
static public final String HORIZONTAL_WHITESPACE = "[\\p{Blank}\\u200B\\u2060\\uFFEF]"

Answer 6

Put the regex below in the find section and select Regular Expression from "Search Mode":
[^\S\r\n]+

Answer 7

m/ /g just give space in / /, and it will work. Or use \S — it will replace all the special characters like tab, newlines, spaces, and so on.