while, until & select in Bash

From the Bash Scripting cheat sheet · Loops · verified Jul 2026

Condition-driven loops and reading input.

bash

# Quick Reference
while [[ $n -lt 5 ]]; do (( n++ )); done
until [[ -f ready ]]; do sleep 1; done
while read -r line; do echo "$line"; done < file

💡 while IFS= read -r line; do ... done < file is THE safe way to read lines.

⚡ IFS= prevents trimming whitespace; -r stops backslash mangling in read.

📌 until is while's inverse - it loops until the condition succeeds.

🟢 break leaves the loop entirely; continue jumps to the next iteration.

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