 ,    .       ,
      .     , 
     .    
 ,      .

$ cat < supply-orders

 2000  :      10/7/02
 1   :   10/14/02
 5   : 10/28/02
 12   :    10/4/02
$

. 7.10.  cat    

    noclobber (.  "noclobber:  
"  9),     
   .      -
   noclobber,       -
 ,         . 
        ,  
noclobber .    noclobber,  -
   echo   ,    noclobber:

$ set - noclobber
$ echo "hi there" > Imp

bash: tmp: Cannot overwrite existing file
(   )
$ set +o noclobber

     II.    
       :

$ cat orange pear > orange

cat: orange: input file is output file(    )

 cat    ,  -  
  orange.       orange -
    ,   pear,  ,   , -
    (>)     
orange.       ,    cat 
   , , ,     nw   -
  ,  :

$ cat orange pear > temp

$ mv temp orange

,    ,  . ,  
,     a, b    apple    
grep (.  "grep:  "  5)   a. output.   -
     a output,      
:

$ grep apple a b  > a output
grep: output: No such file or directory(    )

 7.  I: Bourne Again Shell 231