Java execute shell commands, how to read output in real time?

Question

Through the following code, I can execute and get the shell command, and get the output, but only after the end of the process, can I get the standard output. How can I get the real-time output when the process is executing

         Process process = Runtime.getRuntime().exec(command);
         // close process's output stream.
         process.getOutputStream().close();

         pIn = process.getInputStream();
         InputStreamReader inputStreamReader = new InputStreamReader(pin, "UTF-8");
         bufferedReader = new BufferedReader(inputStreamReader);
         String line = null;
         while ((line = bufferedReader.readLine()) != null) {
             this.buf.append(line + "\n");
         }
        
        process.waitfor();

This question answers yours: https://stackoverflow.com/questions/38821224/java-use-exec-and-read-output-while-program-is-still-running — Pawel Veselov, Apr 15 '21 at 22:07

sanjeevRm · Answer 1 · 2021-04-14T11:59:52.873

0

you can use process builder to read response of command executed

         ProcessBuilder pb = new ProcessBuilder();
            pb.command(cmd);
            Process proc = pb.start();
            proc.waitFor();

            InputStream inputStream = proc.getInputStream();
            BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
            String responseLine = "";
            StringBuilder output = new StringBuilder();
            while (( responseLine = reader.readLine())!= null) {
                output.append(responseLine + "\n");
            }

edited Apr 14 '21 at 11:59

answered Apr 14 '21 at 11:10

sanjeevRm

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Your answer is quite close, but it does not work in real-time because it contains `proc.waitFor();`. hence it first waits for the process to exit and then start processing the output. – Robert Apr 14 '21 at 11:51
I just use this method, but I can't get real-time output – Question Apr 15 '21 at 06:19

score 0 · Answer 2 · answered Aug 09 '23 at 08:40

Here is one way to display the output from the command in real time by redirecting the output to the same as those of the java process.

ProcessBuilder pb = new ProcessBuilder();
pb.command("./a-script.sh")
pb.inheritIO() // 
def proc = pb.start()
proc.waitFor()

Java execute shell commands, how to read output in real time?

2 Answers2