Get Return Code of a Program within a Java Program

In previous post i wrote about shell scripts arguments having spaces. Now, in this post i am writing about how to get return code of a program within a java program.

Problem statement:

Get return code of a program while you execute that program from the java code. This program may be either a shell command/script or another java program.

Get Java Return Code POC:

The following java code snippets are written for this POC.

Program 1:

I have a simple java application which return the same integer as its return code which i pass it as an argument. Following i have shared that.

package com.harisaltaf;

public class ReturnCode {
public static void main(String[] args) {
System.out.println("Returning code=" + args[0]);
System.exit(Integer.parseInt(args[0]));
}
}

Program 2:

I have written another java application which executes this application and get its return code. Following is that piece of code.

package com.harisaltaf;

public class GetReturnCode {
public static void main(String[] args) {
// String[] command = { "./linux_shell_script.sh" };
String[] command = {
"sh",
"-c",
"cd /home/haris/workspace/get_java_return_code"
+ "&& java -cp java_return_code.jar com.harisaltaf.ReturnCode 5" };
ShellExecutor executor = new ShellExecutor();
try {
executor.execute(command);

System.out.println("Command Return Code= "
+ executor.getReturnCode());
System.out.println("Command Result= " + executor.getScriptResult());
System.out.println("Command Error= " + executor.getScriptError());

} catch (Exception e) {
System.out.println(e.getMessage());
}
}

You can see i have written two commands. In first command i am executing the program 1 from a shell script while in second command i am running that directly as a shell command.

Below is the shell script code. Don’t forget to change shell script file writes.

echo ""
echo "---------------------------------------------"

echo "---result of ls:"
cd /home/haris/workspace
ls

echo "---result of java program:"
cd /home/haris/workspace/get_java_return_code
java -cp java_return_code.jar com.harisaltaf.ReturnCode 5

echo "---result of ls again:"
ls
echo "---------------------------------------------"

Output:

Executing Shell Script:

When i run the program with the help of shell script, i get the following output.

Command Return Code= 0
Command Result=
---------------------------------------------
---result of ls:
get_java_return_code
java_return_code
---result of java program:
Returning code=5
---result of ls again:
bin
java_return_code.jar
linux_shell_script.sh
src
---------------------------------------------

Command Error= null

You see in the Java code you didn’t get the correct return code of program 1 in you 2nd java application. The actual code of the program 1 should be equal to 5 as we gave it as input but the returned code of the shell script is 0 as in output “Command Return Code= 0”. This is because when you run some commands from shell script then the return code returned is the return code of the complete shell script not of only the program you specified.

When executing as direct Shell Command:

When i run the program with java command executing directly from java application, i get the following output.

Command Return Code= 5
Command Result= Returning code=5

Command Error= null

You see i get the correct return code now.

Source code:

Download source code from here: get_java_return_code

Shell Script Arguments with Spaces from JAVA

Today i was doing my office work. It was about automating a process by calling shell scripts from java code. I got a very time consuming issue it took my almost 4 hours to resolve it. Actually in start i searched for replacement not for the direct solution.

Problem Statement:

The problem was that whenever you pass some shell script arguments with spaces from java code which have spaces in it the value isn’t passed correctly. It breaks the value at first space. For example:

If you have passed “second argument” form java code then in shell script the statement “export SECOND_PARAM=$2” will set the value of SECOND_PARAM to “second” only.

Shell Script Arguments with Spaces POC:

The following java code snippet is written for this POC.

public static void main(String[] args) {
String userDir = System.getProperty("user.dir");
System.out.println("User dir : " + System.getProperty("user.dir"));
Integer intVal = -1;
String[] command = { "./resources/dumpScript.sh", "firstArgument", "second Argument" };

try {

BufferedReader stdInput = null;
BufferedReader stdError = null;

Process p = Runtime.getRuntime().exec(command);
stdInput = new BufferedReader(new InputStreamReader(p
.getInputStream()));
stdError = new BufferedReader(new InputStreamReader(p
.getErrorStream()));

String line;
System.out.println("===============stdInput================");
line = stdInput.readLine();
while (line != null) {
System.out.println(line);
line = stdInput.readLine();
}
System.out.println("=======================================");

System.out.println("===============stdError================");
line = stdError.readLine();
while (line != null) {
System.out.println(line);
line = stdError.readLine();
}
System.out.println("=======================================");

intVal = p.waitFor();

try {
if (stdInput != null)
stdInput.close();
} catch (Exception ignored) {
}
try {
if (stdError != null)
stdError.close();
} catch (Exception ignored) {
}

} catch (Exception e) {
System.out.println(e.getMessage());
}
System.setProperty("user.dir", userDir);
System.out.println("Current dir : " + System.getProperty("user.dir"));
}

and the following is the shell script written for this POC.

echo "start of the Shell script."

export FIRST_PARAM=$1
export SECOND_PARAM=$2

echo "First arg= " $FIRST_PARAM
echo "Second arg= " $SECOND_PARAM

echo "end of the Shell script."

When i run the code first i got the following output:


User dir : /home/haris/workspace/Shell Script Arguments with Spaces POC
java.io.IOException: Permission denied
Current dir : /home/haris/workspace/Shell Script Arguments with Spaces POC

This was because my shell script file did not have execute permissions on linux. To give permissions to your shell scripts do the following:

Set File permissions in Linux:

cd "path of directory where your shell script is"
chmod 777 dumpScript.sh

After successful execution of my shell script i got the following output:

User dir : /home/haris/workspace/Shell Script Arguments with Spaces POC
===============stdInput================
start of the Shell script.
First arg= firstArgument
Second arg= second
end of the Shell script.
=======================================
===============stdError================
=======================================
Current dir : /home/haris/workspace/Shell Script Arguments with Spaces POC

Here you can see “Second arg= second” You can see in java code snippet that i passed  “second Argument” as argument to this variable but only “second” could be set in the variable.

Solution for shell scripts arguments with spaces:

Change your shell script. Simply add double quotes around “$2”. The new shell script is copied below:

echo "start of the Shell script."

export FIRST_PARAM=$1
export SECOND_PARAM="$2"

echo "First arg= " $FIRST_PARAM
echo "Second arg= " $SECOND_PARAM

echo "end of the Shell script."

After running the program again you can see the correct output. Following snippet shows the correct output i got after this modification.

User dir : /home/haris/workspace/Shell Script Arguments with Spaces POC
===============stdInput================
start of the Shell script.
First arg=  firstArgument
Second arg=  second Argument
end of the Shell script.
=======================================
===============stdError================
=======================================
Current dir : /home/haris/workspace/Shell Script Arguments with Spaces POC

Source Code:

Download code from here: Shell Script Arguments with Spaces POC

References:

http://stackoverflow.com/questions/905891/passing-argument-containing-space-in-shell-script