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 directo-
       ries  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 `.' oc-
       curs 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  environ-
       ment 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.