Grep Command in Linux

Question

Hi all,
I having problem getting the output of grep command in Linux (Red Hat 9.0).
At the same time, I am able to get the output of cat command.
Using the output of cat command, I am writing it to a text file and then in another process using grep I am extracting particular line from the text file.
To get the Process Output I am using a code from http://hacks.oreilly.com/pub/h/1092#thread.
Below is my code.
public void getUSBInfo() {     
       try{
              String catCommand =  "cat /proc/bus/usb/devices";
              System.out.println("catCommand is : "+catCommand);
              Process p = Runtime.getRuntime().exec(catCommand);
              usbInfoBuffer = new StringBuffer("");
              InputStream inStream = p.getInputStream();
              new InputStreamHandler( usbInfoBuffer, inStream ); 
                              // InputStreamHandler is the class used to read the console output.
              StringBuffer errBuffer = new StringBuffer();
              InputStream errStream = p.getErrorStream();
              new InputStreamHandler( errBuffer , errStream );
              p.waitFor();
              catCommandOutput = usbInfoBuffer.toString();
              System.out.println("USB Info : " +catCommandOutput);
              String fileCat ="/EthicsPoint/usbInfo.txt";
              File catCommandOutputFile =  new File(fileCat);
              boolean filesuccess = catCommandOutputFile.createNewFile();
              setContents(catCommandOutputFile,catCommandOutput);
              extractUSBInfo();
              }catch(Exception e) {
             JOptionPane.showMessageDialog(null," Exception occured executing Native Method..catCommand.."                                         ,epname,JOptionPane.ERROR_MESSAGE);                                    System.out.println("File Exception No 6" +e);
public void extractUSBInfo() {
     try {
          String filename = " /EthicsPoint/usbInfo.txt";
          String grepCommand = "grep \"P:\\|S:\""+filename ;
           //String[] grepCommand = new String[]{"grep", "\"P:\\|S:\"", "/EthicsPoint/usbInfo.txt"};
          Process p = Runtime.getRuntime().exec(grepCommand);
          usbExtractedInfoBuffer = new StringBuffer("");
          InputStream inStream = p.getInputStream();
          new InputStreamHandler( usbExtractedInfoBuffer, inStream );
          StringBuffer errBuffer = new StringBuffer();
          InputStream errStream = p.getErrorStream();
          new InputStreamHandler( errBuffer , errStream );
          p.waitFor();
          String Output = usbExtractedInfoBuffer.toString();
          System.out.println("grepCommand is    : " +grepCommand);
          System.out.println("Searched USB Info : " +Output);
      }catch(Exception e) {
     JOptionPane.showMessageDialog(null," Exception occured executing Native Method..grepCommand..."                               ,epname,JOptionPane.ERROR_MESSAGE);                                    System.out.println("File Exception No 7" +e);
      }I am not getting any IOException. The output of System.out.println("Searched USB Info : " +Output); is blank.
If I try shell> grep "P:\|S:" /EthicsPoint/usbInfo.txt, I get the desired output.
What could be the reason ? While using cat command I am getting the output , but grep command is
returning blank. I even tried String array[] for exec() command, but still get blank.
Where and what I am doing wrong ?
Thanks in advance.
Regards,
Jay.

Answer 1

Hi asjf,
Thanks a lot... The problem is finally solved.
String exeCommand = "grep P:\\|S: "+filename; I removed the quotes and it worked. But if I
remove backslash for the pipe symbol nothing happens..as I get return value of 1.
Output after removing quotes :
exeCommand is : grep P:\|S:  /EthicsPoint/usbInfo.txt
Exit Value is : 0
USB Info : P:  Vendor=0000 ProdID=0000 Rev= 0.00
S:  Product=USB OHCI Root Hub
S:  SerialNumber=ce84b000
P:  Vendor=0000 ProdID=0000 Rev= 0.00
S:  Product=USB OHCI Root Hub
S:  SerialNumber=ce849000But I have noticed another problem. If I execute the aplication number of times, eventhough
the exit value is 0, USB Info : is blank. This happens sometimes. Sometimes I get the correct output.
What could be the reason ?
Thanks to you and all who have replied to my queries....Thanks a lot.....Really appreciate the time and effort.
Regards,
Jay.