Had vfork, unless you're on some not-BSD where vfork has remained relevant the last three decades?

DESCRIPTION vfork() was originally used to create new processes without fully copying the address space of the old process, which is horrendously inefficient in a paged environment. It was useful when the purpose of fork(2) would have been to create a new system context for an execve(2). Since fork(2) is now efficient, even in the above case, the need for vfork() has diminished. vfork() differs from fork(2) in that the parent is suspended until the child makes a call to execve(2) or an exit (either by a call to _exit(2) or abnormally). ... HISTORY The vfork() function call appeared in 3.0BSD with the additional semantics that the child process ran in the memory of the parent until it called execve(2) or exited. That sharing of memory was removed in 4.4BSD,