unable to execute terminal command from java code

Question

I want to execute terminal commands,for example cp, from within the java program. The code that I am trying is:

    public String executeCommand(){
Process p;
    String[] str = {"/bin/bash", "-c", "cp", "/Users/Desktop/abc.csv",  "/Users/Desktop/folder1/"};
            try {

                p = Runtime.getRuntime().exec(str);
            //p.waitFor();
            p.waitFor();
            BufferedReader reader =
                    new BufferedReader(new InputStreamReader(p.getInputStream()));

            String line = "";
            while ((line = reader.readLine())!= null) {
                output.append(line + "\n");
            }


            } catch (Exception e) {
                e.printStackTrace();
            }
            System.out.println(output.toString());
            return "Success";
    }

The code executes without error but I do not see file copied at the destination. I also tried to have a single String with the above command instead of having an array but still no success. If I remove /bin/bash then I get error as cannot find cp: no such file or directory.

What am I doing wrong here and how to resolve it?

NOTE: I think that the command is not executed at all as if I for above copy example, even if I give an invalid file location, it does not throw any error and executes like as before without actually executing the command.

UPDATE: I was able to execute cp command by using /bin/cp followed by source and destination. But if I try to execute a command like hadoop fs -put then it does not work. I am trying to execute /usr/bin/hadoop fs -put. I get error as could not find or load main class fs, How do I execute hadoop fs commands?

you get output by putting readLine() then you can find the problem — Madhawa Priyashantha
– Madhawa Priyashantha, Commented Oct 24, 2014 at 16:03
@fastsnail I tried that way also but same result as before. I have edited my post above to include readline(). I do not see anything on my intellij console accept the success message. — user2966197
– user2966197, Commented Oct 24, 2014 at 16:13

Community · Accepted Answer · 2017-05-23 10:33:35Z

3

cannot find cp: no such file or directory. - means that cp not found. Try to specify full path e.g. /bin/cp.

The bash command expects a single argument for -c, however you are passing three of them. Try to pass it in same piece, i.e. {"/bin/bash", "-c", "cp /Users/Desktop/abc.csv /Users/Desktop/folder1/"}.

Alternatively, try some other more concise solution, e.g. Standard concise way to copy a file in Java?

edited May 23, 2017 at 10:33

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answered Oct 24, 2014 at 17:40

kan

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4 Comments

user2966197 Over a year ago

I tried {"/bin/bash", "-c", "cp /Users/Desktop/abc.csv /Users/Desktop/folder1/"} and also {"/bin/cp", "-c", "cp /Users/Desktop/abc.csv /Users/Desktop/folder1/"} but both time same result. It executes without error but nothing gets copied.

user2966197 Over a year ago

I think that the command is not executed at all as if for above copy example, even if I give an invalid file location, it does not throw any error and executes like as before without actually executing the command.

kan Over a year ago

@user2966197 Have you tried /bin/cp? Have you checked getErrorStream()? Usually error messages are printed into stderr, not stdout.

user2966197 Over a year ago

Thanks for the help. I was able to execute cp command by using /bin/cp followed by source and destination. But if I try to execute a command like hadoop fs -put then it does not work. I am trying to execute /usr/bin/hadoop fs -put.

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