I don't know if it is the right way to fix the following pb :

term% pwd
/sys/src/cmd/rc
term% cat /dev/wdir
/sys/src/cmd/rcterm% 
term% @{ cd .. }
term% cat /dev/wdir
/sys/src/cmdterm% 
term% pwd
/sys/src/cmd/rc


Notes:
Fri Mar 10 11:46:08 EST 2006 rsc
    This is definitely not correct.
    You can't re-chdir after every single command.
    That's going to slow tons of stuff, and
    it breaks interacting with acme (try cd /dev/acme/new
    multiple times).
    
    Even rewriting /dev/wdir after every command
    seems like overkill to me.  The vast majority 
    leave /dev/wdir correct.  
    
    I don't think there's a good solution.
    This one creates more problems than it solves
    (as do most).
    


Reference: /n/sources/patch/sorry/rc-restore-wdir-after-fork
Date: Fri Mar 10 00:58:21 CET 2006
Signed-off-by: xigh@free.fr
Reviewed-by: rsc

--- /sys/src/cmd/rc/havefork.c	Fri Mar 10 00:49:47 2006
+++ /sys/src/cmd/rc/havefork.c	Fri Mar 10 00:49:44 2006
@@ -171,10 +171,13 @@
 	}
 }
 
+extern int dochdir(char *);
+
 void
 Xsubshell(void)
 {
 	int pid;
+	char owd[512];
 	switch(pid = fork()){
 	case -1:
 		Xerror("try again");
@@ -184,7 +187,9 @@
 		runq->ret = 0;
 		break;
 	default:
+		getwd(owd, sizeof owd);
 		Waitfor(pid, 1);
+		dochdir(owd);
 		runq->pc = runq->code[runq->pc].i;
 		break;
 	}