Run CMD using /bin/sh -c CMD and return the exit status. The CMD is run synchronously, and Bourne-shell meta characters are interpreted by /bin/sh. E.g., to start CMD in the background, use a trailing "&" character. See also guile's system, but note that it may permit signals on the controlling tty to be seen by children (observed on Linux, Free/NetBSD, but not on Solaris or HP/UX. This may be a bug (not meeting POSIX.2 specifications). Returns the child-pid, or #f if the fork fails.