Regular expression for no white space at start or end, but allow white space in middle, but also allow only one char inputs:

Question

Regular expression for no white space at start or end, but allow white space in middle, but also allow only one char inputs:

The closest I have got is : ^([^\\

Answer 1

Make everything after the first non-space character optional:

^(?=\S)[a-zA-Z0-9_\s-]*\S$

Answer 2

Non-spaces, optionally followed by multiple groups of spaces then non-spaces:

^[^\s]+(\s+[^\s]+)*$

Edit:

To include the character restrictions, just replace non-space classes with allowable characters:

^[-_a-zA-Z0-9]+(\s+[-_a-zA-Z0-9]+)*$

Also, consider being Unicode friendly and using something like

^[-_\p{Alnum}]+(\s+[-_\p{Alnum}]+)*$

(assuming your regex interpreter allows it).