PowerShell REGEX quandry

Question

I'm totally lost on this regex result on PowerShell.
PS C:\Windows\system32> "917021" -match "[0-9]{4}"
True
Also tried this:
PS C:\Windows\system32> "917021" -match "[0-9]{4,5}"
True
According to all the rules in the book, this should limit the string to four characters and in the second case to five characters at the most. In fact, as I read it this is the very reason for the curly braces. Yet PowerShell passes both versions. Can anyone explain this behavior?

Answer 1

You just need to examine the $matches variable. Or $matches[0].

Answer 2

That makes some sense to me, except it seems deceptive that it would return a TRUE if it isn't a complete match, when the whole point of the { } is to limit the set of characters to only 4 (or 5). It seems that the whole point of regex is to filter out mismatches. Let's say I wanted to only send something to servers named 9070 and 90702, but not 907024 and 907025. The script sees that the partial match and returns TRUE, defeating the point of the { }. Doesn't that seem wrong somehow? Forgive me if I'm being a bit dense on this.

Answer 3

Hi,

[0-9]{4} matches 9170 and [0-9]{4,5} matches 91702 so they both return TRUE. To retrieve captured text you could use the $Matches hashtable automatic variable

Best Regards,
Ian Xue

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Answer 4

Thanks all for your input. This is going to take some work, I can see. i am thankful to the community for your patience and help.