Why isn't this function working? (Beginner bash scripting)

Question

So I have a list of a set of numbers going from 1 to 100, I intended to iterate over it to obtain for every number every single number below it. Like 3 = 1 2 3, or 10 = 1 2 3 4 5 6 7 8 9 10. However the function I'm trying to use isn't working.

for i in ${BigList[@]:0:100}
do 
for j in $(echo {1..$i})
do 
echo $j;sleep 1 
done 
done

The following code is outputing

{1..1}
{1..2}
{1..3}
{1..4}

When in fact I was trying to get it to output this: 1 --> 1 2 --> 1 2 3 --> 1 2 3 4. Something like this. The goal is to get all the numbers until that particular one

Does this answer your question? How do I iterate over a range of numbers defined by variables in Bash? — Ruud Helderman
– Ruud Helderman, Commented Jul 17, 2022 at 15:54

chepner · Accepted Answer · 2022-07-17 15:51:14Z

1

$(echo {1..$i}) suffers from the same problem as {1..$i} alone: brace expansion precedes parameter expansion; command substitution does nothing to address that. You could use eval:

for j in eval {1..$i}

but it's better to avoid eval unless absolutely necessary, which it is not here:

for ((j=1; j<=$i; j++))

answered Jul 17, 2022 at 15:51

chepner

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1 Comment

Wiimm Over a year ago

Because of math mode you can write for ((j=1; j<=i; j++)) instead of for ((j=1; j<=$i; j++)).

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