1set prototyped 2hdr vfork 3sys vfork 4 5tst run{ 6 if test "$_hdr_vfork" = 1 7 then echo "#include <vfork.h>" 8 elif test "$_sys_vfork" = 1 9 then echo "#include <sys/vfork.h>" 10 else echo '#include <unistd.h>' > $tmp.c 11 $cc -E $tmp.c | grep vfork 12 fi 13}end 14