Process groups

A terminal may have a foreground process group associated with it. This foreground process group plays a special role in handling signal-generating input characters,
as described in section “Special characters”.

A terminal's foreground process group may be set or examined by a process, assuming the permission requirements in this section are met; see tcgetpgrp() and tcsetpgrp(). The terminal interface aids in this allocation by restricting access to the terminal by processes that are not in the current process group. For further details, see section “Terminal accesscontrol”.