Regular Expressions 101

^start of line

\d{6}a Unicode decimal digit, repeated exactly 6 times

-the literal - (45₁₀ / 55₈ / 2D₁₆)

Positive Lookahead(?=\d{4}$)

\d{4}a Unicode decimal digit, repeated exactly 4 times

$end of line

0+the literal 0 (48₁₀ / 60₈ / 30₁₆) , repeated at least once

Group 1([1-9]\d*)

Character Class[1-9]

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

\d*a Unicode decimal digit, repeated any number of times

$end of line

Global pattern flags

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

m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string

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Search reference

Regular Expression

^\d{6}-(?=\d{4}$)0+([1-9]\d*)$

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