Reading files in command line in java

Question

I am trying to make it so that when a user clicks a button, a new screen appears and automatically runs a command line process, and they are able to see the outputs of this process.

I thought that I might be able to use a JTextArea to set text to.

Here's what I've got at the moment:

runButton.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent r)
            {
                JFrame runFrame = new JFrame("Running process...");
                runFrame.setVisible(true);
                runFrame.setSize(500, 400);
                runFrame.setDefaultCloseOperation(DISPOSE_ON_CLOSE);
                runFrame.setLayout(null);
                JTextArea run = new JTextArea();
                run.setBounds(100,50,300,200);
                runFrame.add(run);
                Runtime runtime = Runtime.getRuntime();
                Process process = null;
                try 
                {
                    process = runtime.exec("cat /cmd/h:/testfile");
                } 
                catch (IOException e) 
                {
                    e.printStackTrace();
                }
                InputStream runStream = process.getInputStream();
                InputStreamReader runStreamReader = new InputStreamReader(runStream);
                BufferedReader br = new BufferedReader(runStreamReader);
                String line;
                StringBuilder sb = new StringBuilder();
                try 
                {
                    while ((line = br.readLine()) != null)
                    {
                        sb.append(line);
                    }
                } 
                catch (IOException e) 
                {
                    e.printStackTrace();
                }
                run.setText(sb.toString());
            }
        });

The error I'm getting with this is:

Cannot run program "cat": CreateProcess error=2, The system cannot find the file specified

I was trying to test opening a file to test this, which just contains lines of random letters.

EDIT:

I'm not sure I explained clearly what I need this to do. What I want is for a command to be run in command line that opens a file. I then want the result of the command line to be output into the JTextArea.

EDIT 2:

I have tried to change my command to "ping riot.de -t". This will ping riots server every so often and it returns a response with the response time.

Upon running this, the new frame is just black, and java freezes up.

Are you running this on Windows? There is no `cat` command on Windows. — Jesper, Sep 19 '16 at 08:42
seems like `/cmd/h:/testfile` doesn't exist. are you running cygwin on windows? — Sharon Ben Asher, Sep 19 '16 at 08:42
I am running on windows @Jesper - what could i use instead of cat? — Plumel, Sep 19 '16 at 08:43
Regardless of the host OS this is not the correct way to open a text file in Java. You don't need to stream the file into stdout to read it. google on how to open text file in Java (hint, `FileReader`) — Sharon Ben Asher, Sep 19 '16 at 08:45
See these two methods of reading files: http://stackoverflow.com/questions/2231369/scanner-vs-bufferedreader — Perry Monschau, Sep 19 '16 at 08:47
See http://stackoverflow.com/questions/18551251/how-to-open-a-text-file — Sharon Ben Asher, Sep 19 '16 at 08:47

score 0 · Answer 1 · answered Sep 19 '16 at 08:45

0

maybe the env of your java application execution has not the right path of cat cmd? you have try to specify absolute path for cat command?

answered Sep 19 '16 at 08:45

aurox

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How would I go about specifying an absolute path? – Plumel Sep 19 '16 at 08:54
Open a terminal and with command: which cat get absolute path of cat command. Try to use that one. I hope I was helpful – aurox Sep 19 '16 at 10:46
Thanks, I will try this. – Plumel Sep 19 '16 at 10:50
You try to run your command cat /cmd/h:/testfile on terminal? works? maybe the dirname "h:" could give any problem... – aurox Sep 19 '16 at 10:56
It came back saying that cat is not recognized as an internal or external command, operable program or batch file. I have changed the command to "ipconfig" and now it is returning correct information – Plumel Sep 19 '16 at 10:57

Reading files in command line in java

1 Answers1