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I'm looking for a regex to validate if numbers are below 20 000. I can't find the right solution, I have so far this:

(^([1-9]([0-9]{0,3})|20000)$)

Which works quite ok but as soon as it gets to 10 000 it gives no matches. So I have a gap from 9 999 - 20 000.

What am I doing wrong? I don't use regex for these situations, but the 3th party program required regex for such..

Thanks!

user1717483
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3 Answers3

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The ([1-9]([0-9]{0,3}) part is designed to match all numbers strictly below 2000 but you define it as: "A digit one to nine followed by zero to three digits". Now 10 000 is a one followed by four zeros: you can rewrite the part as:

[1-9][0-9]{3}|1[0-9]{4}

The full regex is now:

^[1-9][0-9]{3}|1[0-9]{4}|20000$
Willem Van Onsem
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I've got this:

^([01]?\d{0,4}|20000)$

Which match any number from 0 to 20 000 and allow the user to use number with leading 0 Live Demo

Thomas Ayoub
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2

Your regex - ^([1-9]([0-9]{0,3})|20000)$ - matches numbers from 1 till 9999 and 20000.

You may use

^([1-9]\d{0,3}|1\d{4}|20000)$

See demo

Breakdown:

  • ^ - match start of string
  • ([1-9]\d{0,3}|1\d{4}|20000) - match one of the alternatives:
    • [1-9]\d{0,3} - 1 to 9 followed with 0 to 3 any digits (from 1 till 9999)
    • 1\d{4} - 1 followed with any 4 digits (to match 10000 - 19999)
    • 20000 - literally 20000
  • $ - match the end of string
Wiktor Stribiżew
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