  echo     (*)    Bourne
Again Shell   memo      echo:

$ memo=alex*
$ echo "$memo"

alex*

   ,   
,    .     -
   memo,       :

$ Is

alex.report
alex.summary
$ echo $memo

alex.report alex.summary

   ,    memo    ,
      alex*     :

alex.report  alex.summary.

unset:  

   ,     ,   -
,    .    ,    ,
   :

$ persons
$ echo $person

$

       unset.  
 person   :

$ unset $person

readonly:   

    readonly   ,   -
  .     person  
 .         
 ;      .    
        :

$ person=jenny
$ echo $person

jenny

$ readonly person

$ person=helen

bash: person: readonly variable     (   )

   readonly       
,    .      -
,     ,     
,        .

 9.  II: Bourne Again Shell                                            305