Question

5) Write a regular expression would zip code + 4 fields of the forms: xxxxx-xxxx where x is any number but the last 4 digits could be missing. The dash at the end of the first 5 numbers will ALWAYS be present AND the field is delineated with spaces or tabs.

Answer 1

Following is the expression written in "Bash script" (mixture of commands):

^\d{5}(?:[-\s]\d{4})?$

Step-by-step explanation:

• ^ = For staring string (denotation).
• \d{5} = Matching 5 digits (first five unknown x's)
• (?:…) = Making Group (making group of former 5 digits)
• [-\s] = Match a hyphen or a space

(checking if a hyphen is present?)

• \d{4} = Matching 4 digits (next four unknown x's)
• …? = Pattern before it is optional
• $ = Ending of the string.(denotation)