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.
