Regex for currency number, How can I write it shorter?

Question

^((?=.*[1-9]|0)(?:\d{1,3}))((?=.*\d)(?:\.\d{3})?)*((?=.*\d)(?:\,\d\d){1}?){0,1}$

I actually think this regular expression is very long, and mayby could be shorter. The problem is i'm not very good with regular expressions and therefore I ask you for help.

Online regex tester http://regexr.com/3a3mk

My rules:

• Starting with 1, 2 or 3 positive numbers [1-9] or 0.
• Adding as many . (followed by 3 numbers [0-9]) as you want.
• Possibility to add a comma with 2 numbers (as decimals)

Positive results

• 0
• 0,55
• 1
• 1,60
• 10
• 10,70
• 100
• 100,80
• 1,10
• 1.000
• 1.000,20
• 10.000
• 10.000,03
• 100.000
• 100.000,08
• 1.000.000.000
• 1.000.000.000,10

Negative results

• 0,0
• 1,1
• 1,000
• 1000.000
• 0.000
• 0.000,10
• 1.000,1
• 1.000,100
• 1.0,00
• 1.00,00
• 1.000,0
• 01
• 012,10
• 012.123,10
• a
• a0
• 0,a
• 0,aa
• 1.a00.00
• 1.000.a1

[EDIT] Added more negative results

Answer 1

The following should suit your needs:

^(?:0|[1-9]\d{0,2})(?:\.\d{3})*(?:,\d{2})?$

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Answer 2

Edited:

^(0|[1-9][0-9]{0,2}(\.[0-9]{3})*)(,[0-9]{2})?$

matches:

^ beginning of line

[1-9] just one non-zero digit

[0-9]{0,2} between 0 and 2 digits

(\.[0-9]{3})* zero or more lots of a period and 3 digits

(0 | [1-9][0-9]{0,2}(\.[0-9]{3})*) either (i) a zero or (ii) up to three digits (the first not a zero) followed by blocks of zero or more lots of a period followed by three digits

(,[0-9]{2})? zero or one lots of a comma and 2 digits

$ end of line