Bash command output as numeric variable

Question

I do this:

VAL=$(wc -l < file_with_5_lines)
for i in {1..${VAL}}; do echo $i; done

Expecting this result:

Instead of that I get this one:

{1..5}

EDIT

This question was marked as duplicate but the accepted answer for the other question isn't valid in my opinion. The proposed solution is this:

VAL=$(wc -l < file_with_5_lines)

for i in {1..$((VAL))}; do
        echo $i
done

And continues to give me this result:

{1..5}

Instead of:

Just write a normal numeric `for` loop. – John Zwinck Oct 19 '17 at 15:07 — John Zwinck, Oct 19 '17 at 15:07

codeforester · Accepted Answer · 2017-10-19T16:41:39.173

2

Brace expansion is done before parameter expansion and that's why we can't have a variable inside {...} construct. Use a regular for loop so that you don't depend on an external command like seq:

for ((i = 1; i <= VAL; i++)); do
    # your code here
done

edited Oct 19 '17 at 16:41

answered Oct 19 '17 at 15:16

codeforester

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This is the best solution, without external commands – Sergio Oct 20 '17 at 13:57

score 1 · Answer 2 · answered Oct 19 '17 at 15:15

1

Try the below code,

VAL=$(wc -l < file_with_5_lines)
for i in `seq ${VAL}`
do 
  echo $i
done

answered Oct 19 '17 at 15:15

sprabhakaran

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This works fine – Sergio Oct 20 '17 at 13:54

score 0 · Answer 3 · edited Oct 19 '17 at 15:46

0

VAL=$(wc -l < file_with_5_lines)
for i in $(seq $VAL);do echo $i;done

edited Oct 19 '17 at 15:46

gboffi

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answered Oct 19 '17 at 15:20

Buddhi

416
4
14

1

what's wrong here? – Buddhi Oct 19 '17 at 16:30
1

Try here: https://www.jdoodle.com/test-bash-shell-script-online `echo -e "line1\nline2\nline3\nline4\nline5" > input.txt;VAL=$(wc -l < input.txt);for i in $(seq $VAL);do echo $i;done` – Buddhi Oct 19 '17 at 16:44
This works fine – Sergio Oct 20 '17 at 13:56

Bash command output as numeric variable

3 Answers3