         (.
 "PS1:   ()"    ):

$ PS1='$ [$?] '
$ [0] Is xxx

Is: xxx: No such file or directory     (    )
$ [1] pwd
/home/mgs
$ [0]



 ,    Shell,    -
  ,    ,   
       .   -
         
.        , 
      ,    ,
    .       -
  .    ,       ,
    ,      ,  
  .     
history.     ,  :   -
 .



history   .        ( 
   )   ,     ,
       . 
     ,    ,    .

 ,       , 
  HISTSIZE.     500,    
   , , 100.

         ,
   HISTFILE (  .bash_history    -
).          
.   ,   ,  
HISTFILE (      HISTSIZE),  
 HISTFILESIZE (  500).  HISTSIZE  -
 ,    , HISTFILESIZE   -
,   ,  ,   HISTFILE, -
  ,   . . . 9.3.

Bourne Again Shell      
.         bash (. 
"PS1:   ()"    ).   -
    ,    -
     .

322  III.   Red Hat Linux