Loops

Updated September 2026 · Beginner-friendly guide

for over words

Iterate a list. Quote expansions when items may contain spaces—often you loop over "$@" or lines carefully.

for f in *.txt; do
  [[ -e "$f" ]] || continue
  echo "File: $f"
done

Useful for numeric ranges.

for ((i = 1; i <= 3; i++)); do
  echo "$i"
done

Read lines from a file or pipeline. Adjust IFS and -r to handle backslashes.

while IFS= read -r line; do
  echo "Line: $line"
done < input.txt

Loops until a command succeeds—handy for waiting.

until ping -c1 example.com >/dev/null 2>&1; do
  sleep 2
done

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