regex101: Regex to find only numbers

^start of string

Negative Lookahead(?!(^$|[-]{1}[.]{1}|[0]{1}[0-9]+|[-]{1}[0]{1}[0-9]+))

Group 1(^$|[-]{1}[.]{1}|[0]{1}[0-9]+|[-]{1}[0]{1}[0-9]+)

1st Alternative^$

^start of string

$end of string, or before its final line terminator

2nd Alternative[-]{1}[.]{1}

Character Class[-]{1}

{1}matches one character from the set below:

-the literal - (45₁₀ / 55₈ / 2D₁₆)

Character Class[.]{1}

{1}matches one character from the set below:

.the literal . (46₁₀ / 56₈ / 2E₁₆)

3rd Alternative[0]{1}[0-9]+

Character Class[0]{1}

{1}matches one character from the set below:

0the literal 0 (48₁₀ / 60₈ / 30₁₆)

Character Class[0-9]+

+matches at least one character from the set below:

0-9one character from 0 (48₁₀) to 9 (57₁₀)

4th Alternative[-]{1}[0]{1}[0-9]+

Character Class[-]{1}

{1}matches one character from the set below:

-the literal - (45₁₀ / 55₈ / 2D₁₆)

Character Class[0]{1}

{1}matches one character from the set below:

0the literal 0 (48₁₀ / 60₈ / 30₁₆)

Character Class[0-9]+

+matches at least one character from the set below:

0-9one character from 0 (48₁₀) to 9 (57₁₀)

Group 2([\-]{0,1}[1-9]?[0-9]*((\.|\,)[0-9]*)?|[0]((\.|\,)[0-9]*)?)

1st Alternative[\-]{0,1}[1-9]?[0-9]*((\.|\,)[0-9]*)?

Character Class[\-]{0,1}

{0,1}matches at most one character from the set below:

\-the literal - (45₁₀ / 55₈ / 2D₁₆)

Character Class[1-9]?

?matches at most one character from the set below:

1-9one character from 1 (49₁₀) to 9 (57₁₀)

Character Class[0-9]*

*matches any number of characters from the set below:

0-9one character from 0 (48₁₀) to 9 (57₁₀)

Group 3((\.|\,)[0-9]*)?

?repeats the group contents below at most once:

Group 4(\.|\,)

1st Alternative\.

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

2nd Alternative\,

\,the literal , (44₁₀ / 54₈ / 2C₁₆)

Character Class[0-9]*

*matches any number of characters from the set below:

0-9one character from 0 (48₁₀) to 9 (57₁₀)

2nd Alternative[0]((\.|\,)[0-9]*)?

Character Class[0]

0the literal 0 (48₁₀ / 60₈ / 30₁₆)

Group 5((\.|\,)[0-9]*)?

$end of string, or before its final line terminator

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

Search reference

Regular Expression

^(?!(^$|[-]{1}[.]{1}|[0]{1}[0-9]+|[-]{1}[0]{1}[0-9]+))([\-]{0,1}[1-9]?[0-9]*((\.|\,)[0-9]*)?|[0]((\.|\,)[0-9]*)?)$

New

-0.123122342765172635778687

Regular Expressions 101

Regular Expression

Substitution