9.25 The C Shell repeat Command

The C shell has a built-in command that lets you execute a command repeatedly:

% 

repeat 



n command

All you do is specify the number of repetitions, followed by the command you want to re-execute. A trivial example would be:

% 

repeat 4 echo Enter name:


Enter name:
Enter name:
Enter name:
Enter name:

Simple, right? Just imagine what Jack Nicholson could have done in the movie The Shining if he had traded in his typewriter for a UNIX system:

% 

repeat 500 echo "All work and no play makes Jack a dull boy."

Ok, this is fun at first, but you may soon wonder whether this command has any down-to-earth uses. It does, and I'll conclude with some more useful examples:

1. Print three copies of memo :

   % 
   
   repeat 3 pr memo | lp
   
   

2. Run popd ( 14.6 ) four times to clear a directory stack:

   % 
   
   repeat 4 popd
   
   

3. Append 50 boilerplate files to report :

   % 
   
   repeat 50 cat template >> report
   
   

Some versions of the C shell repeat command have a quoting bug. See the end of article 47.2 .