bash shell脚本：sed：如何在运行时用变量替换路径

Question

#!/bin/sh


JAVA_DIR=/opt/bmc
echo "Editing $PRONTO_BIN/httpmon, setting correct java path to $PW_DIR/jre/bin/java"
sed -i 's/"$install_dir\/jre\/jre"/"$JAVA_DIR"/g' httpmon1 > httpmon2
echo "done"

这有什么问题