How to pipe a string argument to an executable launched with Apache Commons Exec?

Question

I need to pipe a text argument to the stdin of a command launched with Apache Commons Exec (for the curious, the command is gpg and the argument is the passphrase to the key

Answer 1

Hi to do this i will use a little helper class like this: https://github.com/Macilias/Utils/blob/master/ShellUtils.java

basically you can than simulate the pipe usage like shown here before without calling the bash beforehand:

public static String runCommand(String command, Optional dir) throws IOException {
    String[] commands = command.split("\\|");
    ByteArrayOutputStream output = null;
    for (String cmd : commands) {
        output = runSubCommand(output != null ? new ByteArrayInputStream(output.toByteArray()) : null, cmd.trim(), dir);
    }
    return output != null ? output.toString() : null;
}

private static ByteArrayOutputStream runSubCommand(ByteArrayInputStream input, String command, Optional dir) throws IOException {
    final ByteArrayOutputStream output = new ByteArrayOutputStream();
    CommandLine cmd = CommandLine.parse(command);
    DefaultExecutor exec = new DefaultExecutor();
    if (dir.isPresent()) {
        exec.setWorkingDirectory(dir.get());
    }
    PumpStreamHandler streamHandler = new PumpStreamHandler(output, output, input);
    exec.setStreamHandler(streamHandler);
    exec.execute(cmd);
    return output;
}