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Regex matches all but one digit

What would be the regex to match - or not match - all but one digit?

For example,

  • stack

    must match
  • stack overflow

    must match
  • 12389237

    should match but
  • 2

    shouldn't match

I'm on ^[^\d]+$

, but apparently it doesn't meet my third condition.

EDIT:

This is for PHP, by the way.

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6 answers


Break it down into two cases. Any of these matches a single character that is not a digit, or matches any string of length 2 or greater:



^(\D|.{2,})$
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The easiest way is to simply negate the match for a single digit using normal programming logic:

 ! /(?<!\d)\d(?!\d)/

Coding what in one template is possible but annoying:

/^(?!.*(?<!\d)\d(?!\d))/

or expand through /x

:

/ ^ (?! .* (?<! \d) \d (?! \d) )/x

Or isolated from various multi-line circumstances:

 / \A (?! .* (?<! \d) \d (?! \d) )/sx

See why I said denying a regular positive match is easier?

Here's a test program:

use v5.12;
while (<DATA>) {
    my $got =  / ^ (?! .* (?<! \d) \d (?! \d) )/x;
    print $got ? "PASS" : "FAIL";
    print ": ", $_;

}
__END__
"stack" should match
"stack overflow" should match
"12389237" should match but
"2" should not match

What produces:

PASS: "stack" should match
PASS: "stack overflow" should match
PASS: "12389237" should match but
FAIL: "2" should not match


EDIT

If you misdiagnosed your question and if you just meant that the strings are actually

stack
stack overflow
12389237
2

instead, the simple thing then is to deny a single digit match:

! /^\d$/

or more carefully,

! /\A\d\z/

Constructing an operation ɴᴏᴛ in a template is never pretty.

/^ (?! \d $ )/x

Here's another test program:

use v5.12;
while (<DATA>) {
    my $got =  /^ (?! \d $ )/x;
    print $got ? "PASS" : "FAIL";
    print ": $_";

}
__END__
stack
stack overflow
12389237
2

which reports:

PASS: stack
PASS: stack overflow
PASS: 12389237
FAIL: 2
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Doesn't match a single digit, inverting the match:

!/^\d\z/

Or just a negative regex:

/^(?!\d\z)/
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Does it have to be a regular expression? For php you like this

is_integer($string) && $string < 10
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The following regex will match a string (including space) and any number that is not a single digit:

/^[a-zA-z\s]+|[0-9]{2,}$/gm

RegExr Code

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while(my $line = <DATA>){
    chomp $line;
    if ($line !~ /^\d{1}$/) {
        print "$line    match\n";
    }
    else {
        print "$line    NOT match\n";
    }
}

__DATA__
stack
stack overflow
12389237
2

Result:

perl regex.pl
stack   match
Qaru  match
12389237        match
2       NOT match
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