set prototyped
hdr vfork
sys vfork
tst run{
if test "$_hdr_vfork" = 1
then echo "#include <vfork.h>"
elif test "$_sys_vfork" = 1
then echo "#include <sys/vfork.h>"
else echo '#include <unistd.h>' > $tmp.c
$cc -E $tmp.c | grep vfork
fi
}end