Version Comparison in Shell

Context: Installer update scripts needed to compare semantic versions to decide whether to download a newer release or skip because the installed version is current. Date: December 2025

The Problem

Comparing semantic versions in bash is non-trivial. String comparison fails ("1.9.0" > "1.10.0" is true lexicographically but wrong semantically). Splitting on dots and comparing numerically works but is verbose and error-prone with pre-release suffixes.

The Solution

Use GNU sort -V (version sort) which handles semantic versioning correctly:

version_compare() {
  local current="${1#v}"   # Strip 'v' prefix
  local latest="${2#v}"

  if [[ "$current" == "$latest" ]]; then
    return 0  # Same version
  elif [[ $(printf '%s\n' "$current" "$latest" | sort -V | head -n1) == "$current" ]]; then
    return 1  # Current is older (update available)
  else
    return 2  # Current is newer
  fi
}

Key Learnings

  • sort -V is available in GNU coreutils (macOS via Homebrew, standard on Linux) and handles all semver edge cases
  • Always strip the v prefix before comparing (v1.2.3 → 1.2.3)
  • Fail-safe default: if version check fails (API rate limit, missing binary, network error), proceed with installation rather than skipping — a redundant install is better than a stale binary
  • Use FORCE_INSTALL=true to trigger version checking mode in installers (repurposes existing flag)
  • See management/common/lib/version-helpers.sh for the canonical implementation