How do I iterate over a range of numbers defined by variables in Bash?

Question

How do I iterate over a range of numbers in Bash when the range is given by a variable?

I know I can do this (called "sequence expression" in the Bash documentation):

 for i in {1..5}; do echo $i; done 

Which gives:

1
2
3
4
5

Yet, how can I replace either of the range endpoints with a variable? This doesn't work:

END=5 for i in {1..$END}; do echo $i; done 

Which prints:

{1..5}

Answer 1

for i in $(seq 1 $END); do echo $i; done

edit: I prefer seq over the other methods because I can actually remember it ;)

Answer 2

The seq method is the simplest, but Bash has built-in arithmetic evaluation.

END=5 for ((i=1;i<=END;i++)); do     echo $i done # ==> outputs 1 2 3 4 5 on separate lines 

The for ((expr1;expr2;expr3)); construct works just like for (expr1;expr2;expr3) in C and similar languages, and like other ((expr)) cases, Bash treats them as arithmetic.