Build Strings with { }

I've been finding more and more uses for the {} pattern-expansion characters in csh, tcsh, and bash. (Other shells can use {}, too; see article .) They're similar to *, ?, and [] (), but they don't match filenames the way that *, ?, and [] do. You can give them arbitrary text (not just filenames) to expand - that "expand-anything" ability is what makes them so useful.

Here are some examples to get you thinking:

• To fix a typo in a filename (change fixbold5.c to fixbold6.c):
  
  

  % mv fixbold{5,6}.c
  

  An easy way to see what the shell does with {} is by adding echo () before the mv:

  % echo mv fixbold{5,6}.c mv fixbold5.c fixbold6.c
  

  
  
  
• To copy filename to filename.bak in one easy step:
  
  

  % cp filename{,.bak}
  

  
  
  
• To print files from other directory(s) without retyping the whole pathname:
  
  

  % lpr /usr3/hannah/training/{ed,vi,mail}/lab.{ms,out}
  

  That would give lpr () all of these files:

  /usr3/hannah/training/ed/lab.ms /usr3/hannah/training/ed/lab.out /usr3/hannah/training/vi/lab.ms /usr3/hannah/training/vi/lab.out /usr3/hannah/training/mail/lab.ms /usr3/hannah/training/mail/lab.out
  

  in one fell swoop!

• To edit ten new files that don't exist yet:
  
  

  % vi /usr/foo/file{a,b,c,d,e,f,g,h,i,j}
  

  That would make /usr/foo/filea, /usr/foo/fileb, ... /usr/foo/filej. Because the files don't exist before the command starts, the wildcard vi /usr/foo/file[a-j] would not work ().

• An easy way to step through three-digit numbers 000, 001, ..., 009, 010, 011, ..., 099, 100, 101, ... 299 is:

  foreach	foreach n ({0,1,2}{0,1,2,3,4,5,6,7,8,9}{0,1,2,3,4,5,6,7,8,9}) ...Do whatever with the number $n... end

  Yes, csh also has built-in arithmetic, but its @ operator () can't make numbers with leading zeros. This nice trick shows that the {} operators are good for more than just filenames.

• To create sets of subdirectories:
  
  

  % mkdir man % mkdir man/{man,cat}{1,2,3,4,5,6,7,8} % ls -F man cat1/ cat3/ cat5/ cat7/ man1/ man3/ man5/ man7/ cat2/ cat4/ cat6/ cat8/ man2/ man4/ man6/ man8/
  

  
  
  
• To print ten copies of the file project_report (if your lpr () command doesn't have a -#10 option):
  
  

  % lpr project_repor{t,t,t,t,t,t,t,t,t,t}
  

  
  
  

- JP