Shell Commands From PL/SQL

Using a Java stored procedure it is possible to perform shell commands from PL/SQL:

Create the Java Stored Procedure
Publish the Java call specification
Grant Privileges
Test It.
Known Issues.

Create the Java Stored Procedure

First we need to create the Java class to perform the shell command.

CREATE OR REPLACE AND COMPILE JAVA SOURCE NAMED "Host" AS
import java.io.*;
public class Host {
  public static void executeCommand(String command) {
    try {
      String[] finalCommand;
      if (isWindows()) {
        finalCommand = new String[4];
        // Use the appropriate path for your windows version.
        finalCommand[0] = "C:\\windows\\system32\\cmd.exe";  // Windows XP/2003
        //finalCommand[0] = "C:\\winnt\\system32\\cmd.exe";  // Windows NT/2000
        finalCommand[1] = "/y";
        finalCommand[2] = "/c";
        finalCommand[3] = command;
      }
      else {
        finalCommand = new String[3];
        finalCommand[0] = "/bin/sh";
        finalCommand[1] = "-c";
        finalCommand[2] = command;
      }
  
      final Process pr = Runtime.getRuntime().exec(finalCommand);
      pr.waitFor();

      new Thread(new Runnable(){
        public void run() {
          BufferedReader br_in = null;
          try {
            br_in = new BufferedReader(new InputStreamReader(pr.getInputStream()));
            String buff = null;
            while ((buff = br_in.readLine()) != null) {
              System.out.println("Process out :" + buff);
              try {Thread.sleep(100); } catch(Exception e) {}
            }
            br_in.close();
          }
          catch (IOException ioe) {
            System.out.println("Exception caught printing process output.");
            ioe.printStackTrace();
          }
          finally {
            try {
              br_in.close();
            } catch (Exception ex) {}
          }
        }
      }).start();
  
      new Thread(new Runnable(){
        public void run() {
          BufferedReader br_err = null;
          try {
            br_err = new BufferedReader(new InputStreamReader(pr.getErrorStream()));
            String buff = null;
            while ((buff = br_err.readLine()) != null) {
              System.out.println("Process err :" + buff);
              try {Thread.sleep(100); } catch(Exception e) {}
            }
            br_err.close();
          }
          catch (IOException ioe) {
            System.out.println("Exception caught printing process error.");
            ioe.printStackTrace();
          }
          finally {
            try {
              br_err.close();
            } catch (Exception ex) {}
          }
        }
      }).start();
    }
    catch (Exception ex) {
      System.out.println(ex.getLocalizedMessage());
    }
  }
  
  public static boolean isWindows() {
    if (System.getProperty("os.name").toLowerCase().indexOf("windows") != -1)
      return true;
    else
      return false;
  }

};
/

show errors java source "Host"

Publish the Java call specification

Next we publish the call specification using a PL/SQL "wrapper" PL/SQL procedure.

CREATE OR REPLACE PROCEDURE host_command (p_command  IN  VARCHAR2)
AS LANGUAGE JAVA 
NAME 'Host.executeCommand (java.lang.String)';
/

Grant Privileges

The relevant permissions must be granted from SYS for JServer to access the file system.

EXEC DBMS_JAVA.grant_permission('SCHEMA-NAME', 'java.io.FilePermission', '<<ALL FILES>>', 'read ,write, execute, delete');
EXEC Dbms_Java.Grant_Permission('SCHEMA-NAME', 'SYS:java.lang.RuntimePermission', 'writeFileDescriptor', '');
EXEC Dbms_Java.Grant_Permission('SCHEMA-NAME', 'SYS:java.lang.RuntimePermission', 'readFileDescriptor', '');

The affects of the grant will not be noticed until the grantee reconnects.

Test It

Finally we call the PL/SQL procedure with our command text.

SET SERVEROUTPUT ON SIZE 1000000
CALL DBMS_JAVA.SET_OUTPUT(1000000);
BEGIN
  host_command (p_command => 'move C:\test1.txt C:\test2.txt');
END;
/

The same result could be achieved with COM Automation but in my opinion this method is much neater.

The output from the host command can be captured using the DBMS_OUTPUT.get_lines procedure.

DECLARE
  l_output DBMS_OUTPUT.chararr;
  l_lines  INTEGER := 1000;
BEGIN
  DBMS_OUTPUT.enable(1000000);
  DBMS_JAVA.set_output(1000000);

  host_command('dir C:\');

  DBMS_OUTPUT.get_lines(l_output, l_lines);

  FOR i IN 1 .. l_lines LOOP
    -- Do something with the line.
    -- Data in the collection - l_output(i)
    NULL;
  END LOOP;
END;
/

Known Issues

Depending on the environment, the process may continue running as a zombie after the command has been executed, even if the destroy() method is called manually. If this happens the process is only cleaned up when the session ends. Under normal circumstances this doesn't represent a problem, but when called as part of a job the zombie processes will only die when the Job Queue Coordinator is stopped.

Hope this helps. Regards Tim...

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