bash: executing an output of a script as a script

Question

I\'m writing a simple script to generate all combinations of a and b of a given length (say 10). I want to be able to do this on a command line (I know this is fairly easy i

Answer 1

You can do for i in $(seq $n) instead of seq 1 1 $n.

You can do for ((i=1; i<=$n; i++)) and avoid calling an external utility.

You can do this (slightly hacky with only one loop):

$ a=A; b=B; n=4; s=''; for ((i=1;i<=n;i++)); do s+="{$a..$b}"; done; eval echo "''" $s"$'\n'"

or this (highly hacky without any loops):

$ a=A; b=B; n=4; eval echo "''" $(printf "{$a..$b}%.0s" $(eval echo "{1..$n}"))"$'\n'"

Either one will get you this:

 AAAA
 AAAB
 AABA
 AABB
 ABAA
 ABAB
 ABBA
 ABBB
 BAAA
 BAAB
 BABA
 BABB
 BBAA
 BBAB
 BBBA
 BBBB

Answer 2

You need to use an eval, $() gives you a string.

eval $( echo echo foo )

Another option is to stick into a subshell and pipe it to a bash:

(echo echo foo) | /bin/bash