regex - Regular expression to match alphanumeric, hyphen, underscore and space string -

i'm trying match string contains alphanumeric, hyphen, underscore , space.

hyphen, underscore, space , numbers optional, first , last characters must letters.

for example, these should match:

abc abc def abc123 ab_cd ab-cd

i tried this:

^[a-za-z0-9-_ ]+$

but matches space, underscore or hyphen @ start/end, should allow in between.

use simple character class wrapped letter chars:

^[a-za-z]([\w -]*[a-za-z])?$

this matches input starts , ends letter, including single letter.

there bug in regex: have hyphen in middle of characters, makes character range. ie [9-_] means "every char between 9 , _ inclusive.

if want literal dash in character class, put first or last or escape it.

also, prefer use of \w "word character", letters , numbers , underscore in preference [a-za-z0-9_] - it's easier type , read.

Camp