• 1,2,3,4 - Should pass
• 1, - Should fail
• 1.2,1,4,5 - Should pass
• 1.,2 - Should fail
• 1.2,1.2 - Should pass
• .5,.5 - Should fail

CodePudding user response：

As the regex flavor is not specified, let me first assume PCRE. Then would you please try:

^\d (?:\.\d )?(?:,\d (?:\.\d )?)*$

• \d (?:\.\d )? matches one or more digits optionally followed by a dot and one or more digits.
• (?:,\d (?:\.\d )?)* matches zero or more units which consists of a comma and the number defined as above.
• ^ and $ anchor the start/end of the string individually.

Demo

In case of ERE you can say instead:

^[0-9] (\.[0-9] )?(,[0-9] (\.[0-9] )?)*$