Your 'xterm&; xterm&;' has a few issues to point out. First, you do not need the semi-colon at all. And second, you are spawning processes that need to connect to an X server, which is where the "user interface" lives for them. "User interface" was just ambiguous here, methinks. No file descriptors are passed around with creating background processes; those are possible only when done programatically, although there are exceptions. OK, so I looked for the rest, especially the "reverse" setting of "tostop". There isn't one. All of what I know, and likely all of what exists, is here: https://www.ibm.com/support/knowledgecenter/en/SSLTBW_2.1.0/com.ibm.zos.v2r1.bpxa400/bpxug212.htm