More files related to user-level file servers.

Also add acme!

src/lib9/post9p.c

@@ -0,0 +1,40 @@
+#include <u.h>
+#include <libc.h>
+
+int
+post9pservice(int fd, char *name)
+{
+	int i;
+	char *ns, *s;
+	Waitmsg *w;
+
+	if((ns = getns()) == nil)
+		return -1;
+	s = smprint("unix!%s/%s", ns, name);
+	free(ns);
+	if(s == nil)
+		return -1;
+	switch(rfork(RFPROC|RFFDG)){
+	case -1:
+		return -1;
+	case 0:
+		dup(fd, 0);
+		dup(fd, 1);
+		for(i=3; i<20; i++)
+			close(i);
+		execlp("9pserve", "9pserve", "-u", s, (char*)0);
+		fprint(2, "exec 9pserve: %r\n");
+		_exits("exec");
+	default:
+		w = wait();
+		close(fd);
+		free(s);
+		if(w->msg && w->msg[0]){
+			free(w);
+			werrstr("9pserve failed");
+			return -1;
+		}
+		free(w);
+		return 0;
+	}
+}