如何以编程方式检查是否使用Java在ubuntu上安装了软件实用程序

Question

I am working on a Java Project for my own learning, what i have made is a class which can both read and write to external process using Runtime.getRuntime().exec(cmd);

Now i was wondering is there any special way of checking if a particular software/tool is installed on the system.

Like i use sshpass utility to remotely login to other machines, and if it is not there already i would like to install it using my program. But for this how should i go about checking if it exists there or not?

The idea i have in my mind is to run the command and see the response, if the returned string matches particular expression based on that i would decide it's existence or non-existence.

Do you think it is the right approach or is there any other way to find out this?

Like on windows, i think there are cmdline utilities like ftype, assoc etc, thank you,

Answer 1

In Ubuntu/Debian you can use :

dpkg -s packagname

to see if a package is installed. Then you can parse the output of the command in your app.

Answer 2

If you already know the name of the software binary (which is usually the same to process name) you can use which command.

You can test it in bash/shell which firefox /usr/bin/firefox

Also I can supply you an example written in C# of bash output reading:

string output = string.Empty;

string output = string.Empty;

try
{
    // Sets up our process, the first argument is the command
    // and the second holds the arguments passed to the command
    ProcessStartInfo ps = new ProcessStartInfo("bash");
    ps.Arguments = "-c 'firefox'";
    ps.UseShellExecute = false;

    // Redirects the standard output so it reads internally in out program
    ps.RedirectStandardOutput = true;

    // Starts the process
    using (Process p = Process.Start(ps))
    {
        // Reads the output to a string
        output = p.StandardOutput.ReadToEnd();

        // Waits for the process to exit must come *after* StandardOutput is "empty"
        // so that we don't deadlock because the intermediate kernel pipe is full.
        p.WaitForExit();
    }
}
catch
{
    // TODO manage errors
}

If the bash output is multi-line you can pre-filter it by piping to the grep command:

ps.Arguments = "-c 'cpuid | grep MySearchTerm'";

EDIT 1: Reply to comments

The major problem is the software installation, which requires "administrative" rights. I've tried to create a workaround, but the following line breaks all code:

process = Runtime.getRuntime().exec(new String[]{"/bin/bash","-c","'echo RIadminXsrv1 | sudo -S apt-get install telnet -qy'"});

While in terminal the following command will actually attempt to install telnet (you might have to insert your user into /etc/sudoers to reproduce it on your PC).

/bin/echo myUserPass | /usr/bin/sudo -S /usr/bin/apt-get install telnet -qy

In java it will simply print ( echo output) the remaining part of the command:

myUserPass | /usr/bin/sudo -S /usr/bin/apt-get install telnet -qy

This happens because we are simply executing /bin/echo command with a lot of parameters. I thought that it is possible to actually run the entire set of commands using bash:

bash -c '/bin/echo myUserPass | /usr/bin/sudo -S /usr/bin/apt-get install telnet -qy'

..but it's not, because bash -c '..' in Java doesn't work like it should. It says that -c 'echo ...' script file can not be found, so I suppose that it misinterprets -c option. BTW I have never had this kind of problem in Mono C#.

Here is the entire snippet:

package javaapplication1;

import java.io.*;

public class JavaApplication1 {

    public static void main(String[] args) {

        Process process;
        String softwareToCheck = "telnet"; // Change here

        try
        {       
            if(!_softwareExists(softwareToCheck))
            {
                System.out.println("Installing missing software..");
                process = Runtime.getRuntime().exec(new String[]{"/bin/bash","-c","'echo RIadminXsrv1 | sudo -S apt-get install telnet -qy'"});

                try
                {
                    process.waitFor();
                }
                catch(InterruptedException e)
                {
                    System.out.println(e.getMessage());
                }

                if(!_softwareExists(softwareToCheck))
                {
                    System.out.println("Software is still missing!");
                }

            }
            else
            {
                System.out.println("Software is installed!");
            }
        }
        catch(IOException e)
        {
            System.out.println(e.getMessage());
        }        
    }

    private static boolean _softwareExists(String binaryName) throws IOException
    {
        String line;
        ProcessBuilder builder;
        BufferedReader reader;
        Process process;

        builder = new ProcessBuilder("/usr/bin/which", binaryName);
        builder.redirectErrorStream(true);
        process = builder.start();
        reader = new BufferedReader(new InputStreamReader(process.getInputStream()));
        try
        {
            process.waitFor();
        }
        catch(InterruptedException e) {
            System.out.println(e.getMessage());
        }

        while ((line = reader.readLine ()) != null)
        {
            break; // Reads only the first line
        }

        return (line != null && !line.isEmpty());

    }
}

Answer 3

I am not aware of any tool that could help if package management tool does not report installation correctly. It could be that the some tools are installed but not updated the database.

It may be useful to check if your target executable exists in any directories in $PATH and standard location.

  String pathString = System.getenv("PATH");
   String[]  dirs= pathString.split(':');
   String[]  exes= { "name1", "name2" ....};

   for ( String exename : exes) {
     for ( String dirname : dirs) {
             File exeFile=new File( dirname, exename);
             //do some checks if file exists etc.
     }
   }