Question

On a rooted android device, I tried to run a cat command that read kernel log, as follow:

Process p = Runtime.getRuntime().exec("su");
p = Runtime.getRuntime().exec("/system/bin/cat /proc/kmsg");

The su command was successfully executed but not the cat.
I tried to read the output of the command using getInputStream() but nothing was there, as follow:

BufferedReader in = new BufferedReader(new InputStreamReader(p.getInputStream()));
 while ((read = err.read(buffer)) > 0)
 {  //read error to buffer 
catOutput.append(buffer, 0, read);
 }
 in.close();

I used the same code with ls command instead of displaying the kernel log, it worked just fine and show me the result.

I wonder if what error I am getting and wantted to see the error message on the shell when executing the cat command. Tried the p.getErrorStream() but it doesn’t give me any result.
Could any one help me with this ? Thanks.

Answer 1

I finally found the solution for the problem by using RootTools library.
Recently released (few months after my question was asked), RootTools provides a easy-to-use tool set that helps running commands that required root privilege. I created a wrapper to check if root access is available before executing shell command:

void testRootToolsCommand(String command){

    if (RootTools.isRootAvailable())
        toastMessage("Root is available !!!");
    else { 
        toastMessage("NO ROOT !!! ");
        return; 
    }

    int timeOut = 1000; 
    try {
        List<String> output = RootTools.sendShell(command,timeOut);     
        toastMessage("OUTPUT of the command \n" + output.toString());           
    } catch (RootToolsException re) {
        toastMessage("Funny thing happened with RootTools!!! ");            
    } catch (TimeoutException te)
    {
        toastMessage("Timeout exception - Increase timeout !!! !!! ");
    }
    catch (Exception e) { 
    toastMessage(e.getMessage().toString());
    }       
}

An example of a function call is:

testRootToolsCommand("cat /proc/kmsg > /sdcard/jun11_4h51.txt");

Note: The Tool also support running multiple commands at once.