Bash 3.00 brace expansion

Ah, finally: no more of

for i in 1 2 3 4 5 6 7 8 9 0
do
.. whatever
done

With Bash 3.0, we now have brace expansion for lists:

for i in {1..10} ; do echo $i ; done

Prior to this, we sometimes used "seq", which could result in such awful things as:

for i in `seq 65 69`; do echo -e `printf '\\%03o' $i`; done

Ugly. The Bash 3.0 way is so much cleaner:

for i in {A..E}; do echo $i;done

This also works for more traditional brace expansion use:

$  echo foo{1..4}bar
foo1bar foo2bar foo3bar foo4bar
# used to be done as
$ echo foo{1,2,3,4}bar
foo1bar foo2bar foo3bar foo4bar

Nesting of course still works:

echo foo{bar{1..3},-is-done}
foobar1 foobar2 foobar3 foo-is-done

and you can use it for such tasks as:

mkdir {A..D}{1..3}{0-9} 

which would have required nested loops before Bash 3.0.

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Comments




Mon Oct 3 07:31:46 2005: Subject:   drag
Oh.. that's nice. (I am sure somebody will come along and point out that ksh or other 'alternative' shell had it first, but still this is cool) :P







Mon Oct 3 13:09:30 2005: Subject: nested expansion was knowledge   infinity
never knew that this kind of facility was available.


thanks!



Mon Oct 3 13:20:49 2005: Subject:   TonyLawrence
Well, nested brace expansion has worked before now, but the list expansion in braces is new. Combining both is pretty darn powerful as you see above..





Wed Apr 15 14:24:41 2009: Subject: Increment   anonymous


Hi,

Is there anyway to specify an increment in the brace expansion?



Wed Apr 15 15:51:46 2009: Subject:   TonyLawrence


Yes, you can use a numeric increment; see http://www.gnu.org/software/bash/manual/html_node/Brace-Expansion.html

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