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devexamples

Parse Options With getopts

Parse short options and their arguments with getopts so a shell script exposes a predictable CLI instead of positional guesswork.

BashCli Tooling

Code

snippet
#!/usr/bin/env bash
set -euo pipefail

verbose=false
output=""
level=1

while getopts ":vo:l:h" opt; do
  case "${opt}" in
    v) verbose=true ;;
    o) output="${OPTARG}" ;;
    l)
      level="${OPTARG}"
      if ! [[ "${level}" =~ ^[1-9]$ ]]; then
        echo "level must be 1-9" >&2
        exit 2
      fi
      ;;
    h)
      echo "usage: $0 [-v] [-o output] [-l level] input"
      exit 0
      ;;
    :)
      echo "option -${OPTARG} requires an argument" >&2
      exit 2
      ;;
    \?)
      echo "unknown option: -${OPTARG}" >&2
      exit 2
      ;;
  esac
done
shift $((OPTIND - 1))
input="${1:?input file is required}"

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