The sp-open command leaves the next spooler entry generated by the current process open upon completion of the output generating process. Any subsequent (printer) output is attached to the end of the open entry, until an sp-close command or an sp-assign command is issued.
When no entry number displays, this is attached to the open entry.
sp-open block-print "this is " (p entry # 133 block-print "a test" (p sp-close [1140] Your open files were closed.