Regex for a-z, 0-9, . and -

Question

Can someone tell me what the syntax for a regex would be that would only allow the following characters:

• a-z (lower case only)
• 0-9
• period, dash, underscore

Additionally the string must start with only a lower case letter (a-z) and cannot contain any spaces or other characters than listed above.

Thank you in advance for the help, Justin

Answer 1

You can do: "^[a-z][-a-z0-9\._]*$"

Here is the breakdown

• ^ beginning of line
• [a-z] character class for lower values, to match the first letter
• [-a-z0-9\._] character class for the rest of the required value
• * zero or more for the last class
• $ end of String

Answer 2

^[a-z][a-z0-9._\s-]*

Answer 3

[-._a-z0-9]

or

[-.[:lower:][:digit:]]

or ...

depends on which version of regular expressions you aim for.