[SOLVED] Regular expression to validate field structure

Issue

I would like to implement a regular expression in linux that using grep allows me to verify that a field contains 15 numerical values and that the value occupying the fifth position (starting from left) is either a 5 or a 6.

I have reached the point of defining the requirement that it contains a maximum of 15 values, however, I can not get that the one that occupies the fifth position is a 5 or 6. It would be:

grep -E "^[0-9]{1,15}"

Any idea?

Solution

For exactly 15 numbers, and the 5 position is either 5 or 6:

grep -E "^[0-9]{4}[56][0-9]{10}$"

• ^ Start of string
• [0-9]{4} Match 4 digits
• [56] Match either 5 or 6
• [0-9]{10} Match 10 digits
• $ End of string

To match at least the first 5 characters followed by 0-10 digits after it, and allow a partial match like matching 123462222233333 in 12346222223333344444

grep -Eo "^[0-9]{4}[56][0-9]{0,10}"

Answered By - The fourth bird

Answer Checked By - Dawn Plyler (WPSolving Volunteer)