Java with shell Script

Question

I am writing a Java program from which I am executing a shell script. The shell script is calling another shell script. I am trying to print output returned by child script to parent shell script. Below is my code.

public class App 
{
 public static void main( String[] args ) throws IOException, InterruptedException 
 {
 String command = new String("/home/Test.sh"); 
 Runtime rt = Runtime.getRuntime();
 Process process = rt.exec(command); 
 process.waitFor(1, TimeUnit.MINUTES);
 BufferedReader reader = new BufferedReader(new InputStreamReader( 
 process.getInputStream())); 
 String s; 
 while ((s = reader.readLine()) != null) { 
 System.out.println("Script output: " + s); 
 } 

Shell Script: Test.sh

#!/bin/bash
 result=$( bash myscript.sh )
 echo "$result"

myscript.sh

 #!/bin/bash
 echo "50"

I am getting empty output. I initial thought it might be because the Java process is not waiting for the shell script to finish. So added waitFor() but still no use. Can some one kindly help.

• Nicolas Filotto: check the error stream because it works on my side with your code
• Mustafa DOGRU: try this; result=$( bash /home/myscript.sh ) , full path of myscript.sh

Answer 1

try this; this is not waiting problem.

#!/bin/bash
 result=$( bash /home/myscript.sh ) # full path of myscript
 echo "$result"

Also handle bash error as below;

public static void main(String[] args) throws IOException {
 String command = new String("/tmp/1/Test.sh"); 
 Runtime rt = Runtime.getRuntime();
 Process process = rt.exec(command);
 BufferedReader reader = new BufferedReader(new InputStreamReader( 
 process.getInputStream()));
 String s; 
 while ((s = reader.readLine()) != null) { 
 System.out.println("Script output: " + s); 
 }
 BufferedReader stdError = new BufferedReader(new 
 InputStreamReader(process.getErrorStream()));
 System.out.println("Here is the standard error\n");
 while ((s = stdError.readLine()) != null) {
 System.out.println(s);
 }
 }

adduser tests;

1- myscript.sh:

#!/bin/bash
adduser test
echo "50"

java console output;

Script output: 50
Here is the standard error of the command (if any):
adduser: Only root may add a user or group to the system.

2- myscript.sh:

#!/bin/bash
sudo adduser test
echo "50"

java console output;

Script output: 50
Here is the standard error of the command (if any):
sudo: no tty present and no askpass program specified

3-
myscript.sh:

#!/bin/bash
echo -e "YOURPASSWORD=\n" | sudo -S adduser -shell /bin/bash --home /home/test test
echo -e "YOURPASSWORD\n" | sudo deluser --remove-home test
echo "OK"

java console output;

Script output: Adding user `test' ...
Script output: Adding new group `test' (1002) ...
Script output: Adding new user `test' (1001) with group `test' ...
Script output: Creating home directory `/home/test' ...
Script output: Copying files from `/etc/skel' ...
Script output: Try again? [y/N] Changing the user information for test
Script output: Enter the new value, or press ENTER for the default
Script output: Full Name []: Room Number []: Work Phone []: Home Phone []: Other []: Is the information correct? [Y/n] Looking for files to backup/remove ...
Script output: Removing files ...
Script output: Removing user `test' ...
Script output: Warning: group `test' has no more members.
Script output: Done.
Script output: OK
Here is the standard error of the command (if any):
[sudo] password for ..: Enter new UNIX password: Retype new UNIX password: passwd: Authentication token manipulation error
passwd: password unchanged
Use of uninitialized value $answer in chop at /usr/sbin/adduser line 563.
Use of uninitialized value $answer in pattern match (m//) at /usr/sbin/adduser line 564.
Use of uninitialized value $answer in chop at /usr/sbin/adduser line 589.
Use of uninitialized value $answer in pattern match (m//) at /usr/sbin/adduser line 590.

• Learner: Thank you.. Adding the full path helped. I like to understand the bash error handling. What kind of errors will be captured? Say I am using "adduser" command in script, "only root users will be able to add new users" error will be thrown if not an root user. Will that be captured here?
• Mustafa DOGRU: Yes, that will be captured. Also I try to some test as above; Maybe this can be help