Q:

Increase the amount of brace expansions given a number

I have a program that uses a brace expansion:
for X in {a..z}
    do echo $X;
done

I want to increase the amount of letters used in the brace expansion with a provided number. For example if the number 3 is provided:
for X in {a..z}{a..z}{a..z}
    do echo $X;
done

If the number 5 is provided:
for X in {a..z}{a..z}{a..z}{a..z}{a..z}
    do echo $X;
done

How can I do this in bash?

A:

Here's one way. With a..z:
$ a2z() { 
  k=""
  n=$1
  while [ $n -gt 0 ]
  do
    k="{a..z}$k"
    let n="$n-1"
  done
  echo $(eval "echo $k")
}
$ for X in $(a2z 3)
do echo $X;
done
aaa
aab
aac
...

Kinda useful, or at least interesting, using 0..1 as it shows each permutation for N bits.
$ bitperms() {
  k=""
  n=$1
  while [ $n -gt 0 ] 
  do
    k="{0..1}$k"
    let n="$n-1"
  done
  echo $(eval "echo $k")
}
$ bitperms 4
0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011 1100 1101 1110 1111
$ for X in $(bitperms 2);do echo "$X";done
00
01
10
11

