I am having a problem with builtin sequences (ie: not using seq) in Bash when the seq number is a variable. For example, this works and print me 1 2 3:
for i in {1..3};do
echo $i
done
but this :
a=3
for i in {1..$a};do
echo $i
done
fail and print me {1..3} only
This works with ZSH and I know I have an alternative to make a counter thing but wondering if this is a bug or a brace expansion feature!
In Bash, brace expansion is performed before variable expansion. See Shell Expansions for the order.
$ a=7; echo {1..3} {4..$a}
1 2 3 {4..7}
If you want to use a variable, use C-style for
loops as in Shawn's answer.
An alternative would be to use the double-parenthesis construct which allows C-style loops:
A=3
for (( i=1; i<=$A; i++ )); do
echo $i
done
$ num=3
$ for i in $( eval echo {1..$num});do echo $i;done
1
2
3
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