cd[dir]cd[-]cd[old new]
With no arguments, change to home directory of user.
Otherwise, change working directory to dir. If dir is a
relative pathname but is not in the current directory, then the CDPATH
variable is searched. The last two command forms are specific to the
Korn shell, where - stands for the previous directory.
The third syntax modifies the current directory name
by replacing string old with new,
then switches to the resulting directory.
$pwd/usr/spool/cron $cd cron uucp# cd prints the new directory /usr/spool/uucp