NACSE - Re-Executing Commands


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Re-Executing Commands

While none of us gets the respect he or she deserves, Unix at least listens and remembers what we say-as witnessed by the C and K shell's history command. This command not only recalls your previous commands but also lets you re-execute and even repair them (better than going around saying, ``Gee I wish I had said that.''):
        

% history   	You issue the history (or his) command.    
30 ls   	Here's your list.    
31 cd comphy/book/chapters   	   
32 ftp bigblue   	   
33 mail   	   
34 print malebox   	   
35 history   	The history command above.   
%

Notice that the commands are listed in the numerical order in which they have been issued during the present login. As a result, the last one, number 35, is at the bottom of the list. Some uses of this list are:

REPEAT COMMANDS
!!
Repeat last command (csh).
!n
Repeat command number n (csh).
!pattern
Repeat command starting with pattern (csh).
^ old^ new^
Change old to new in last command.
!n:s/old/new/
Repeat command n with substitution (csh).
r
Repeat last command (ksh).
r n
Repeat command number n (ksh).
r pattern
Repeat command starting with pattern (ksh).

Here are some examples which show that if you know history, you may relive it:

% history   	Tell me my last commands.   
 ls   	This is the 30th command since login.   

 cd comphy/book/chapters   	   
 ftp bigblue   	   

 mail   	   

 print malebox   	   

 history   	This is the command given last.   
%    	Your turn.   
% !!   	Repeat last command (or r).   

 history   	Unix tells you what's going on.   

 cd comphy/book/chapters   	  Here's your history again.   

 ftp bigblue   	   

 mail   	   

 print malebox   	   

 history   	   

 history   	2 history's since you repeated it.   
% !31   	Repeat command #31.   
31 cd comphy/book/chapters    	Unix tells you what's going on.   
%    	Your turn.   
% !f   	Repeat previous f... command.   
32 ftp bigblue    	Command #32 is being repeated.   
^ male^ mail^    	Correcting spelling of male.   
print mailbox   	Corrected command.    
% !31/book/BOOK   	Rerun # 31, substitute for book.   
% cd comphy/BOOK/chapters   	The corrected command.


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Next: Command Line Editing Up: Interactive Shell Tips Previous: Interactive Shell Tips