implements nvm which

nvm.sh

@@ -547,6 +547,7 @@ nvm() {
       echo "    nvm unalias <name>          Deletes the alias named <name>"
       echo "    nvm copy-packages <version> Install global NPM packages contained in <version> to current version"
       echo "    nvm unload                  Unload NVM from shell"
+      echo "    nvm which [<version>]       Display path to installed node version"
       echo
       echo "Example:"
       echo "    nvm install v0.10.24        Install a specific version number"
@@ -949,6 +950,40 @@ nvm() {
     "current" )
       nvm_version current
     ;;
+    "which" )
+      INPUT=$2
+
+      if [ "_$2" != '_system' ]; then
+        VERSION="$(nvm_version "$INPUT")"
+      else
+        VERSION="$INPUT"
+      fi
+      if [ -z "$VERSION" ]; then
+        nvm help
+        return 127
+      fi
+
+      if [ "_$VERSION" = '_system' ]; then
+        if nvm_has_system_node && nvm deactivate >/dev/null 2>&1; then
+          echo $(dirname `which node`)
+          return
+        else
+          echo "System version of node not found." >&2
+          return 127
+        fi
+      elif [ "_$VERSION" = "_∞" ]; then
+        echo "The alias \"$2\" leads to an infinite loop. Aborting." >&2
+        return 8
+      fi
+
+      local NVM_VERSION_DIR
+      NVM_VERSION_DIR="$(nvm_version_path "$VERSION")"
+      if [ ! -d "$NVM_VERSION_DIR" ]; then
+        echo "$VERSION version is not installed yet" >&2
+        return 1
+      fi
+      echo $NVM_DIR/$VERSION
+    ;;
     "alias" )
       mkdir -p "$NVM_DIR/alias"
       if [ $# -le 2 ]; then