Add a script to get Java version which wrote a JAR

ctrueden · ctrueden · commit e3a6f97e4042 · 2014-10-21T14:36:59.000-05:00
diff --git a/class-version.sh b/class-version.sh
@@ -0,0 +1,46 @@
+#!/bin/sh
+
+# class-version.sh - find the Java version which wrote a JAR file
+
+for jar in "$@"
+do
+  # find the first class of the JAR
+  class="$(jar tf "$jar" | grep '\.class' | head -n 1 | sed 's/\//./g' | sed 's/\.class$//')"
+  info="$(javap -verbose -classpath "$jar" "$class")"
+
+  # extract major.minor version
+  minor="$(echo "$info" | grep 'minor version: ' | sed 's/.*minor version: //')"
+  major="$(echo "$info" | grep 'major version: ' | sed 's/.*major version: //')"
+  case $major in
+    45)
+      version="JDK 1.1"
+      ;;
+    46)
+      version="JDK 1.2"
+      ;;
+    47)
+      version="JDK 1.3"
+      ;;
+    48)
+      version="JDK 1.4"
+      ;;
+    49)
+      version="J2SE 5.0"
+      ;;
+    50)
+      version="J2SE 6.0"
+      ;;
+    *)
+      if [ "$major" -gt 50 ]
+      then
+        version="J2SE $(expr $major - 44)"
+      else
+        java="Unknown"
+      fi
+      ;;
+    
+  esac
+
+  # report the results
+  echo "$jar: $version ($major.$minor)"
+done
