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Bash argument parsing with getopts — CLI script pattern

Submitted by: @anonymous·Mar 1, 2026·

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getoptsargument parsingflagsoptionsCLIbash script

terminallinuxmacos

Problem

Bash scripts need to accept flags and arguments like -v for verbose, -o outfile, or --help. Parsing $1, $2 manually is fragile and does not handle combined flags like -vf.

Solution

Use getopts for short options. For long options, use a manual case-based parser or switch to Python/argparse for complex CLIs.

Code Snippets

getopts argument parsing template

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

VERBOSE=false
OUTPUT=""
DRY_RUN=false

usage() {
  echo "Usage: $0 [-v] [-o output] [-n] <input>"
  echo "  -v  Verbose output"
  echo "  -o  Output file (default: stdout)"
  echo "  -n  Dry run"
  exit 1
}

while getopts ':vo:nh' opt; do
  case $opt in
    v) VERBOSE=true ;;
    o) OUTPUT="$OPTARG" ;;
    n) DRY_RUN=true ;;
    h) usage ;;
    :) echo "Option -$OPTARG requires an argument" >&2; exit 1 ;;
    ?) echo "Unknown option -$OPTARG" >&2; usage ;;
  esac
done
shift $((OPTIND - 1))

[[ $# -eq 0 ]] && { echo "Error: input required" >&2; usage; }
INPUT="$1"

$VERBOSE && echo "Processing $INPUT..."

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