rbenv · mislav · May 1, 2026 · Mar 21, 2026 · Apr 29, 2026 · May 1, 2026
diff --git a/README.md b/README.md
@@ -42,11 +42,13 @@ PREFIX=/usr/local ./ruby-build-*/install.sh
 # As a standalone program
 $ ruby-build --list                        # lists latest stable releases for each Ruby
 $ ruby-build --definitions                 # lists all definitions, including outdated ones
-$ ruby-build 3.2.2 ~/.rubies/ruby-3.2.2    # installs Ruby 3.2.2
-$ ruby-build -d ruby-3.2.2 ~/.rubies       # alternate form for the previous example
+$ ruby-build 3.4.9 ~/.rubies/ruby-3.4.9    # installs Ruby 3.4.9
+$ ruby-build -d ruby-3.4.9 ~/.rubies       # alternate form for the previous example
+$ ruby-build -d ruby-3.4 ~/.rubies         # installs latest Ruby 3.4.x
 
 # As an rbenv plugin
-$ rbenv install 3.2.2  # installs Ruby 3.2.2 to ~/.rbenv/versions/3.2.2
+$ rbenv install 3.4.9  # installs Ruby 3.4.9 to ~/.rbenv/versions/3.4.9
+$ rbenv install 3      # installs latest Ruby 3.x
 ```
 
 > [!WARNING]
@@ -61,6 +63,28 @@ Basically, what ruby-build does when installing a Ruby version is this:
 
 Depending on the context, ruby-build does a little bit more than the above: for example, it will try to link Ruby to the appropriate OpenSSL version, even if that means downloading and compiling OpenSSL itself; it will discover and link to Homebrew-installed instances of some libraries like libyaml and readline, etc.
 
+### Ruby versions
+
+When listing "latest" Ruby versions, such as in `ruby-build --list` output, ruby-build only knows of Ruby versions that are bundled with this project. That means that when a new Ruby version comes out, ruby-build will not know about it immediately— you will have to upgrade ruby-build before you can use it to install the new Ruby version. This is because ruby-build bundles [definition files](#custom-build-definitions) for each individual Ruby version.
+
+If it's important to you that your installer tool always consults remote resources to download the list of latest Ruby versions (without having to upgrade the tool itself), check out [ruby-install][] as an alternative to ruby-build.
+
+### Ruby implementations
+
+ruby-build ships with definitions for the following Ruby implementations, denoted by version prefixes in the `ruby-build --list` output:
+
+- [CRuby][]: listed in ruby-build as unprefixed version numbers in the `X.Y.Z` format. This is the main Ruby implementation that most people use and is also historically known as "MRI". ruby-build allows adding the `ruby-` prefix to CRuby version numbers for compatibility with other version managers.
+
+- `jruby`: [JRuby][] is a high-performance Ruby implementation with real threading built on top of the Java virtual machine (JVM).
+
+- `mruby`: [mruby][] is a lightweight, embeddable Ruby implementation for microcontrollers.
+
+- `picoruby`: [PicoRuby][] is an alternative mruby implementation for one-chip microcontrollers.
+
+- `truffleruby`: The Native standalone distribution of [TruffleRuby][], an implementation of Ruby on top of GraalVM's Truffle framework.
+
+- `truffleruby+graalvm`: The JVM standalone distribution of TruffleRuby.
+
 ### Advanced Usage
 
 #### Custom Build Definitions
@@ -197,3 +221,9 @@ Be sure to include the full build log for build failures.
   [wiki]: https://github.com/rbenv/ruby-build/wiki
   [build-env]: https://github.com/rbenv/ruby-build/wiki#suggested-build-environment
   [issue tracker]: https://github.com/rbenv/ruby-build/issues
+  [cruby]: https://www.ruby-lang.org/
+  [truffleruby]: https://truffleruby.dev/
+  [picoruby]: https://github.com/picoruby/picoruby#readme
+  [mruby]: https://mruby.org/
+  [jruby]: https://www.jruby.org/
+  [ruby-install]: https://github.com/postmodern/ruby-install#readme
diff --git a/bin/rbenv-install b/bin/rbenv-install
@@ -134,8 +134,6 @@ done
 
 [ "${#ARGUMENTS[@]}" -le 1 ] || usage 1 >&2
 
-unset VERSION_NAME
-
 # The first argument contains the definition to install. If the
 # argument is missing, try to install whatever local app-specific
 # version is specified by rbenv. Show usage instructions if a local
@@ -144,6 +142,12 @@ DEFINITION="${ARGUMENTS[0]}"
 [ -n "$DEFINITION" ] || DEFINITION="$(rbenv-local 2>/dev/null || true)"
 [ -n "$DEFINITION" ] || usage 1 >&2
 
+if VERSION_NAME="$(ruby-build --resolve "$DEFINITION")"; then
+  DEFINITION="$VERSION_NAME"
+else
+  unset VERSION_NAME
+fi
+
 # Define `before_install` and `after_install` functions that allow
 # plugin hooks to register a string of code for execution before or
 # after the installation process.

diff --git a/bin/ruby-build b/bin/ruby-build
@@ -2,10 +2,12 @@
 #
 # Usage: ruby-build [-dvpk] <definition> <prefix> [-- <configure-args...>]
 #        ruby-build {--list|--definitions}
+#        ruby-build --resolve <version>
 #        ruby-build --version
 #
 #   -l, --list      List latest stable releases for each Ruby
 #   --definitions   List all local definitions, including outdated ones
+#   --resolve       Print the latest stable definition name matching a version prefix
 #   --version       Show version of ruby-build
 #
 #   -d, --dir       Install the Ruby in <prefix>/<definition> instead of <prefix>
@@ -1411,6 +1413,36 @@ list_maintained_versions() {
   } | extract_latest_versions | sort_versions | uniq
 }
 
+# resolve a version prefix to the exact version name for which exists a
+# definition file. Example: "ruby-3" => "3.4.9"
+resolve_version() {
+  local version="${1#ruby-}"
+
+  # Look for an exact match first.
+  for DEFINITION_DIR in "${RUBY_BUILD_DEFINITIONS[@]}"; do
+    if [ -f "${DEFINITION_DIR}/${version}" ]; then
+      echo "$version"
+      return 0
+    fi
+  done
+
+  local grep_pattern="${version%.}"
+  if [ "$grep_pattern" = "ruby" ]; then
+    # Special case to select the latest CRuby.
+    grep_pattern="[0-9]"
+  else
+    grep_pattern="$(tr 'A-Z' 'a-z' <<<"${grep_pattern//./\\.}")"
+  fi
+
+  version=$(list_definitions | \
+    grep -e "^${grep_pattern}[-.]" | \
+    grep -v -e '-rc[0-9]*$' -e '-preview[0-9]*$' -e '-dev$' | \
+    tail -n 1)
+
+  [ -n "$version" ] || return 1
+  echo "$version"
+}
+
 extract_latest_versions() {
   # sort in this function looks redundunt but it is necessary
   # rbx-3.99 appears latest unless the sort
@@ -1453,6 +1485,14 @@ for option in "${OPTIONS[@]}"; do
   "l" | "list")
     EARLY_EXIT=list_maintained_versions
     ;;
+  "resolve")
+    if [ "${#ARGUMENTS[*]}" -eq 1 ]; then
+      EARLY_EXIT=resolve_version
+    else
+      echo "ruby-build: '--resolve' needs an argument" >&2
+      EARLY_EXIT=usage_error
+    fi
+    ;;
   "d" | "dir")
     APPEND_DEFINITION_TO_PREFIX=true
     ;;
@@ -1503,12 +1543,9 @@ if [ "${#EXTRA_ARGUMENTS[@]}" -gt 0 ]; then
   RUBY_CONFIGURE_OPTS_ARRAY=("${EXTRA_ARGUMENTS[@]}")
 fi
 
-if [ "$APPEND_DEFINITION_TO_PREFIX" = "true" ]; then
-  if [ -p "$DEFINITION_PATH" ]; then
-    echo "ruby-build: using named pipes in combination with \`--dir' is not possible" >&2
-    EARLY_EXIT=usage_error
-  fi
-  PREFIX_PATH="$PREFIX_PATH/$(basename "$DEFINITION_PATH")"
+if [[ "$APPEND_DEFINITION_TO_PREFIX" = "true" && -p "$DEFINITION_PATH" ]]; then
+  echo "ruby-build: using named pipes in combination with \`--dir' is not possible" >&2
+  EARLY_EXIT=usage_error
 fi
 
 case "$EARLY_EXIT" in
@@ -1521,6 +1558,10 @@ version | list_definitions | list_maintained_versions )
   "$EARLY_EXIT"
   exit 0
   ;;
+resolve_version )
+  resolve_version "${ARGUMENTS[0]}" || exit 1
+  exit 0
+  ;;
 usage_error )
   echo >&2
   usage 1 >&2
@@ -1533,30 +1574,29 @@ usage_error )
   ;;
 esac
 
+VERSION_NAME_PREFIX=""
+
 # expand the <definition> argument to full path of the definition file
 if [[ ! -f "$DEFINITION_PATH" && ! -p "$DEFINITION_PATH" ]]; then
+  if ! VERSION_NAME="$(resolve_version "$DEFINITION_PATH")"; then
+    echo "ruby-build: definition not found: ${DEFINITION_PATH}" >&2
+    exit 2
+  fi
+
+  if [[ $DEFINITION_PATH == ruby-* && $VERSION_NAME != ruby-* ]]; then
+    VERSION_NAME_PREFIX="ruby-"
+  fi
+
   for DEFINITION_DIR in "${RUBY_BUILD_DEFINITIONS[@]}"; do
-    if [ -f "${DEFINITION_DIR}/${DEFINITION_PATH}" ]; then
-      DEFINITION_PATH="${DEFINITION_DIR}/${DEFINITION_PATH}"
+    if [ -f "${DEFINITION_DIR}/${VERSION_NAME}" ]; then
+      DEFINITION_PATH="${DEFINITION_DIR}/${VERSION_NAME}"
       break
     fi
   done
+fi
 
-  # If the given definition is like ruby-X.Y.Z, search again with X.Y.Z
-  if [[ "$DEFINITION_PATH" =~ ^ruby-[0-9] ]]; then
-    DEFINITION_PATH="${DEFINITION_PATH#ruby-}"
-    for DEFINITION_DIR in "${RUBY_BUILD_DEFINITIONS[@]}"; do
-      if [ -f "${DEFINITION_DIR}/${DEFINITION_PATH}" ]; then
-        DEFINITION_PATH="${DEFINITION_DIR}/${DEFINITION_PATH}"
-        break
-      fi
-    done
-  fi
-
-  if [ ! -f "$DEFINITION_PATH" ]; then
-    echo "ruby-build: definition not found: ${DEFINITION_PATH}" >&2
-    exit 2
-  fi
+if [ "$APPEND_DEFINITION_TO_PREFIX" = "true" ]; then
+  PREFIX_PATH="$PREFIX_PATH/${VERSION_NAME_PREFIX}$(basename "$DEFINITION_PATH")"
 fi
 
 # normalize the <prefix> argument