cd [ -qsLP ] [ arg ]
cd [ -qsLP ] old new
cd [ -qsLP ] {+|-}n
       Change the current directory.  In the first form, change the
       current directory to arg, or to the value of $HOME if arg is not
       specified.  If arg is `-', change to the previous directory.

       Otherwise, if arg begins with a slash, attempt to change to the
       directory given by arg.

       If arg does not begin with a slash, the behaviour depends on
       whether the current directory `.' occurs in the list of
       directories contained in the shell parameter cdpath.  If it does
       not, first attempt to change to the directory arg under the
       current directory, and if that fails but cdpath is set and
       contains at least one element attempt to change to the directory
       arg under each component of cdpath in turn until successful.  If
       `.' occurs in cdpath, then cdpath is searched strictly in order so
       that `.' is only tried at the appropriate point.

       The order of testing cdpath is modified if the option POSIX_CD is
       set, as described in the documentation for the option.

       If no directory is found, the option CDABLE_VARS is set, and a
       parameter named arg exists whose value begins with a slash, treat
       its value as the directory.  In that case, the parameter is added
       to the named directory hash table.

       The second form of cd substitutes the string new for the string
       old in the name of the current directory, and tries to change to
       this new directory.

       The third form of cd extracts an entry from the directory stack,
       and changes to that directory.  An argument of the form `+n'
       identifies a stack entry by counting from the left of the list
       shown by the dirs command, starting with zero.  An argument of the
       form `-n' counts from the right.  If the PUSHD_MINUS option is
       set, the meanings of `+' and `-' in this context are swapped.  If
       the POSIX_CD option is set, this form of cd is not recognised and
       will be interpreted as the first form.

       If the -q (quiet) option is specified, the hook function chpwd and
       the functions in the array chpwd_functions are not called.  This
       is useful for calls to cd that do not change the environment seen
       by an interactive user.

       If the -s option is specified, cd refuses to change the current
       directory if the given pathname contains symlinks.  If the -P
       option is given or the CHASE_LINKS option is set, symbolic links
       are resolved to their true values.  If the -L option is given
       symbolic links are retained in the directory (and not resolved)
       regardless of the state of the CHASE_LINKS option.

chdir  Same as cd.
