Plan 9 from Bell Labs’s /usr/web/sources/contrib/anothy/src/lib/djb-ape/unix/tryshsgr.c
main() { short x[4]; x[0] = x[1] = 1; if (getgroups(1,x) == 0) if (setgroups(1,x) == -1) _exit(1); if (getgroups(1,x) == -1) _exit(1); if (x[1] != 1) _exit(1); x[1] = 2; if (getgroups(1,x) == -1) _exit(1); if (x[1] != 2) _exit(1); _exit(0); }