@dbroad 's message is the way to go -- QSELECT doesn't have a command-line version as some commands do. And to expand, it's going to involve Relational Tests [read about them -- the (-4) codes in (ssget) filter lists] comparing values. See the DXF Reference on the codes for entity properties [lineweight is among the "Common Group Codes" item at the top; the width ones are within the LWPOLYLINE entry].
For lineweights other than ByLayer, try this:
(sssetfirst nil (ssget "_X" '((0 . "LWPOLYLINE") (-4 . ">") (370 . 0))))
For global widths other than zero [which can only be greater than zero]:
(sssetfirst nil (ssget "_X" '((0 . "LWPOLYLINE") (-4 . ">") (43 . 0))))
For starting width other than zero [likewise]:
(sssetfirst nil (ssget "_X" '((0 . "LWPOLYLINE") (-4 . ">") (40 . 0))))
[I did it for the lineweight by checking for a value greater than zero, because there's no specific value for ByLayer -- the 370 entry isn't even in entity data to look for in that case -- but any value other than that would be numerical and greater than zero.]
You can use those AutoLisp lines in a Script file. If it's the last or only thing in the file, just add an Enter at the end so the last line in the file is a blank line below the [last] code line.
As with QSELECT, those will select/grip/highlight [that's the (sssetfirst nil ...) part] only what they find within the current space. They will find things elsewhere, and if that's something you need, the total findings can be saved to a variable from which you can get to even those not in the current space.
Kent Cooper, AIA