org.sonar.l10n.shellcheck.rules.shellcheck.SC2051.html Maven / Gradle / Ivy

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Bash doesn't support variables in brace range expansions.
Problematic code
for i in {1..$n}
do
  echo "$i"
done

Correct code
for ((i=0; i<n; i++))
do
  echo "$i"
done

Rationale
In Bash, brace expansion happens before variable expansion. This means that brace expansion will not account for variables.
For integers, use an arithmetic for loop instead. For zero-padded numbers or letters, use of eval may be warranted:
from="a" to="m"
for c in $(eval "echo {$from..$to}"); do echo "$c"; done

or more carefully (if from/to could be user input, or if the brace expansion could have spaces):
from="a" to="m"
while IFS= read -d '' -r c
do
  echo "Read $c"
done <  <(eval "printf '%s\0' $(printf "{%q..%q}.jpg" "$from" "$to")")

Exceptions
None (if you're writing for e.g. zsh, you can use a directive to disable this check)
Related Resources

StackOverflow: Variables in bash seq replacement ({1..10})