more robust command invocation via ISABELLE_JDK_HOME or SCALA_HOME (NB: bash exec requires genuine executable, not function);
#!/usr/bin/env bash
#
# Author: Makarius
#
# Augment Java extension directories.
## diagnostics
function fail()
{
echo "$1" >&2
exit 2
}
[ -n "$ISABELLE_HOME" ] || fail "Missing Isabelle settings environment"
## main
isabelle_jdk java \
-classpath "$(jvmpath "$ISABELLE_HOME/src/Tools/JVM/java_ext_dirs.jar")" \
isabelle.Java_Ext_Dirs "$(jvmpath "$ISABELLE_HOME/lib/classes/ext")"