我如何在外壳程序脚本中处理java -cp命令的异常（.sh文件）

Question

I put this command in .sh file:

CP="$1"
"$JAVA_CMD" -cp "$CP" "$MAIN_CLASS" "$@" 

Where CP is the path of the jar file

my problem is:

when CP does not have proper value, and in this instruction it could not find the main class and i will receive this exception:

Exception in thread "main" java.lang.NoClassDefFoundError

how can i handle this exception in shell script?

Answer 1

Perhaps you may find this link helpful: http://www.tldp.org/LDP/abs/html/exit-status.html

Bash contains a built-in variable called $? that contains the exit code of the previously executed command. $? == 0 $? == 0 means the Java program has been executed successfully, and $? != 0 $? != 0 means the Java program threw an exception such as the one in your case.

Answer 2

To replace any error printed to stderr with your own error message, you can suppress your command's stderr (by redirecting to /dev/null ) and print your message instead when your command's exit status is nonzero:

CP="$1"
"$JAVA_CMD" -cp "$CP" "$MAIN_CLASS" "$@" 2>/dev/null || { echo "error: Java exited with nonzero status $?"; exit 1; }

A more verbose way to do this, which is probably more readable to folks relatively new to Bash:

CP="$1"
if ! "$JAVA_CMD" -cp "$CP" "$MAIN_CLASS" "$@" 2>/dev/null; then
    echo "error: Java exited with nonzero status $?"
    exit 1
fi