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Scripting patterns that make security tooling output safe to handle.

15 entries4 groupsRevised 8 Jan 2026

Safety settings

Put these at the top of any script that touches real files.

  • Fail on errors and unset variablesset -euo pipefail
  • Stop on a pipeline that fails partwayset -o pipefail
  • Prevent globbing surprisesIFS=$'\n'
  • Cleanup on exittrap 'rm -rf "$tmp"' EXIT

Loops and pipelines

  • Read a file line by linewhile IFS= read -r line; do echo "$line"; done < hosts.txt
  • Loop over IPs from a scangrep -oE '([0-9]{1,3}\.){3}[0-9]{1,3}' out.gnmap | sort -u | while read -r ip; do echo "$ip"; done
  • Parallel with a limitxargs -a hosts.txt -P 4 -n 1 -I{} sh -c 'echo {}'
  • Progress-free output for pipescmd 2>/dev/null | tee -a run.log

Quoting and expansion

  • Command substitutionts=$(date -u +%Y%m%dT%H%M%SZ)
  • Default value when emptytarget="${TARGET:-192.0.2.10}"
  • Substring and lengthecho "${host:0:8}"
  • Never word-split a listfor f in "${files[@]}"; do :; done

Debugging

  • Trace executionbash -x ./script.sh
  • Syntax check onlybash -n ./script.sh
  • See what a command resolves totype -a nmap; command -v ffuf