Shell script “for” loop syntax

Question

I have the following to work on:

for i in {2..10}

do

    echo "output: $i"

done

It gives the output: 2, output: 3, so on.

Then, tried to run the following:

max=10

for i in {2..$max}

do

    echo "$i"

done

produces with the following:

output: {2..10}

How can I get this compiler to realize it had to be as $max and the other end of this array, not part of the string?

Answer 1

Brace expansion {x..y}, is usually used before any other expansion, so you cannot use this for variable-length sequences.

Instead, use the seq 2 $max method.

for example it would be:

max=10

for i in `seq 2 $max`

do

    echo "$i"

done

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