 

    ,    -
    .      
 ,    .bash_profile  .profile    -
.  ,  ,       -
    ,      . -
, ,    ,   -
      export.

HOME:  

            
.          
  /etc/passwd.         
     HOME.

   cd  ,       -
,      HOME:

$ pwd

/home/alex/laptop

$ echo $HOME

/home/alex

$ cd

$ pwd

/home/alex

     HOME    cd. 
 cd         HOME (-
  ).

,    HOME   , -
        -
  (~).      , 
   Is     laptop :

$ Is ~/laptop

tester    count    lineup

PATH:    

         , 
   ,         
 .       , 
,      ( ) .    -
      ,   ,  
,   .     
   ,             
 (  )      ( -
 ).      PATH.

       PATH   .
      /etc/profile.     -

 9.  II: Bourne Again Shell                                            311