regex accept only numbers code example

Example 1: just number regex

// https://regex101.com/r/qyq3PG/1
// or 
/^[0-9]*$/

Example 2: regex 10 numbers only

@"^\d{10}$"

Example 3: regex all not numbers

echo 1a2b3c | sed 's/[^0-9]//g'	#Replaces all not numbers
abc