Question

I need help writing a regular expression to meet the following requirements:

• start with a letter
• end with a letter or digit
• have as interior characters only letters, digits, underscore and hyphen

The following expression works well with the exception that it allows underscore as the last character. It should only allow a letter or a digit for the last character:

    ^[A-Za-z][\w-]*\w$

Answer 1

Use a Character Class

You can use a POSIX character class for this. In particular, you could use the alphanumeric class, which is shorthand for [A-Za-z0-9]. For example:

^[A-Za-z][\w-]*[[:alnum:]]$