cd [ -sLP ] [ arg ]
cd [ -sLP ] old new
cd [ -sLP ] {+|-}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 value of $OLDPWD,  the  previous
       directory.   If  a directory named arg is not found
       in the current directory and  arg  does  not  begin
       with  a  slash,  search each component of the shell
       parameter cdpath.  If  the  option  CDABLE VARS  is
       set,  and  a parameter named arg exists whose value
       begins with a slash, treat its value as the  direc-
       tory.

       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 direc-
       tory.

       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  -s  option  is  specified,  cd will refuse
       change the currect 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 followed regardless of the
       state of the CHASE LINKS option.

chdir  Same as cd.
