.Q.x

Set by .Q.opt: a list of non-command parameters from the command line, where command parameters are prefixed by -.

~$ q taq.k path/to/source path/to/destn

q)cla:.Q.opt .z.X /command-line arguments
q).Q.x
"/Users/me/q/m64/q"
"path/to/source"
"path/to/destn"