I am creating a custom shell in Java. I have added history to it so that when up arrow is pressed it goes to the previous command, but the up arrow seems to not be working
Here is my code:
public class MyShell {
public static class JavaStringHistory
{
private List<String> history = new ArrayList<String>();
}
public static void main(String[] args) throws java.io.IOException {
JavaStringHistory javaStringHistory = new JavaStringHistory();
javaStringHistory.history.add("");
Integer indexOfHistory = 0;
String commandLine;
BufferedReader console = new BufferedReader
(new InputStreamReader(System.in));
//Break with Ctrl+C
while (true) {
//read the command
System.out.print("Shell>");
commandLine = console.readLine();
javaStringHistory.history.add(commandLine);
//if just a return, loop
if (commandLine.equals(""))
continue;
//history
if (commandLine.equals(KeyEvent.VK_UP))
{
System.out.println("up arrow");
}
//help command
if (commandLine.equals("help"))
{
System.out.println();
System.out.println();
System.out.println("Welcome to the shell");
System.out.println("Written by: Alex Frieden");
System.out.println("--------------------");
System.out.println();
System.out.println("Commands to use:");
System.out.println("1) cat");
System.out.println("2) exit");
System.out.println("3) clear");
System.out.println();
System.out.println();
System.out.println("---------------------");
System.out.println();
}
if (commandLine.equals("clear"))
{
for(int cls = 0; cls < 10; cls++ )
{
System.out.println();
}
}
if(commandLine.startsWith("cat"))
{
System.out.println("test");
//ProcessBuilder pb = new ProcessBuilder();
//pb = new ProcessBuilder(commandLine);
}
else
{
System.out.println("Incorrect Command");
}
if (commandLine.equals("exit"))
{
System.out.println("...Terminating the Virtual Machine");
System.out.println("...Done");
System.out.println("Please Close manually with Options > Close");
System.exit(0);
}
indexOfHistory++;
}
}
}
All I am getting is
Shell>^[[A
Incorrect Command
Shell>
Any thoughts?
There are several problems with your approach:
User blackSmith has mentioned before me that system console handling is platform-dependent when it comes to cursor key handling and similar topics.
BufferedReader.readLine is not a smart choice to use for history cycling in a shell because you want the shell to immediately react to cursor keys and not force the user to press Return or Enter. Reading whole lines is only required for user commands. Thus, you need to scan the keyboard input for each single character or key code and decide by yourself if it is e.g. a cursor key (up/down for history cycling, left/right for cursor movement within the command line) or delete/backspace for command line editing and so forth.
The text strings which are created by reading control characters via readLine can depend on the OS, maybe even on the shell and the character set (UTF-8, ISO-8859-1, US ASCII etc.) on the console.
Built-in shell editing functions like command history might get in the way with readLine, e.g. on Linux I see the "^[[A" stuff for cursor up, on Windows the cursor keys are passed through to the built-in command history feature of cmd.exe. I.e. you need to put the console in raw mode (line editing bypassed and no Enter key required) as opposed to cooked mode (line editing with Enter key required).
Anyway, so as to answer your initial question about how to find out which key codes are produced by BufferedReader.readLine, it is actually quite simple. Just dump the bytes to the console like so:
commandLine = console.readLine();
System.out.println("Entered command text: " + commandLine);
System.out.print ("Entered command bytes: ");
for (byte b : commandLine.getBytes())
System.out.print(b + ", ");
System.out.println();
Under Linux cursor up might be something like "27, 91, 65" or just "91, 65", depending on the terminal. cursor down ends with "66" instead on my system. So you could do something like:
public class MyShell {
private static final String UP_ARROW_1 = new String(new byte[] {91, 65});
private static final String UP_ARROW_2 = new String(new byte[] {27, 91, 65});
private static final String DN_ARROW_1 = new String(new byte[] {91, 66});
private static final String DN_ARROW_2 = new String(new byte[] {27, 91, 66});
// (...)
public static void main(String[] args) throws IOException {
// (...)
// history
else if (commandLine.startsWith(UP_ARROW_1) || commandLine.startsWith(UP_ARROW_2)) {
System.out.println("up arrow");
}
else if (commandLine.startsWith(DN_ARROW_1) || commandLine.startsWith(DN_ARROW_2)) {
System.out.println("down arrow");
}
// (...)
}
}
But all this is just for explanation or demonstration and so as to answer your question - I do like to get the bounty. ;-)
Maybe a way to go is not to re-invent the wheel and use the work of others, e.g. a framework like JLine. It is not perfect either from what I have heard, but goes way further than anything you can develop by yourself in a short time. Someone has written a short introductory blog post about JLine. The library seems to do just what you need. Enjoy!
Update: I gave JLine 2.11 a little try with this code sample (basically the one from the blog post plus tab filename completion:
import java.io.IOException;
import jline.TerminalFactory;
import jline.console.ConsoleReader;
import jline.console.completer.FileNameCompleter;
public class MyJLineShell {
public static void main(String[] args) {
try {
ConsoleReader console = new ConsoleReader();
console.addCompleter(new FileNameCompleter());
console.setPrompt("prompt> ");
String line = null;
while ((line = console.readLine()) != null) {
console.println(line);
}
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
TerminalFactory.get().restore();
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
It works nicely on Windows and Linux, but for me tab completion only works on Linux, not on Windows. Anyway, command history works well on both platforms.
VK_UP is an integer constant, while in.readLine() is a string.
They won't equal each other. Why don't you try to test for the code that appears in console usually when you click up arrow? So like:
if (in.readLine().equals("^[[A"))
and then you could clear the line, and write the command in the arraylist with the highest index.
Also, I tested this and found a bug. Change your if statements besides the first to else if; after any command it will eventually get to the else and display "Incorrect Command"
Related
There are two Linux command line programs (whiptail and dialog) that provide the ability to display a text UI to the user. I would like to call one of these (preferably whiptail) from within my Java application so that the user can select an option from a predefined list. The following SO questions were helpful to me in figuring out how to call a Linux command from within my code:
How to run linux commands in java code?
Want to invoke a linux shell command from Java
These give helpful tips on how to run a typical Linux command (e.g. "ls"), but my case is a little more complicated (I think) due to the text UI that I would like to have display to the user.
To give an idea of what whiptail does and looks like see this.
Start with ProcessBuilder. Each parameter you want to send the command is a separate element in the command list, for example...
import java.io.IOException;
import java.io.InputStream;
public class Test {
public static void main(String[] args) throws IOException, InterruptedException {
ProcessBuilder pb = new ProcessBuilder(
"whiptail", "--title", "Check list example", " --checklist",
"Choose user's permissions", "20", "78", "4",
"NET_OUTBOUND", "Allow connections to other hosts", "ON",
"NET_INBOUND", "Allow connections from other hosts", "OFF",
"LOCAL_MOUNT", "Allow mounting of local devices", "OFF",
"REMOTE_MOUNT", "Allow mounting of remote devices", "OFF");
pb.redirectInput(Redirect.INHERIT);
// I tend to use pb.redirectErrorStream(true);
// which sends the error stream to the input stream, but
// then you'd need to still consume it to get the result
Process p = pb.start();
InputStreamConsumer errorConsumer = new InputStreamConsumer(p.getErrorStream());
Scanner input = new Scanner(System.in);
String option = input.nextLine();
p.getOutputStream().write(option.getBytes());
p.getOutputStream().flush();
int exitCode = p.waitFor();
System.out.println(exitCode);
errorConsumer.join();
System.out.println(errorConsumer.getContent());
}
public static class InputStreamConsumer extends Thread {
private InputStream is;
private StringBuilder content;
public InputStreamConsumer(InputStream is) {
this.is = is;
content = new StringBuilder(128);
}
public String getContent() {
return content.toString();
}
#Override
public void run() {
try {
int value = -1;
while ((value = is.read()) != -1) {
content.append((char)value);
}
} catch (IOException exp) {
exp.printStackTrace();
}
}
}
}
This is very basic, it simply executes the command, consumes it's output into a StringBuilder (to be retrieved later), waits till the command exists and displays the basic results.
Since I don't have access to whiptail, I can't test the code, but if the command is available in the default search path of the OS, it should work, otherwise you'll need to supply the path to the command as part of the first element in the command list
I'm making a game which plays until the user enters quit in the command line.
The user can enter different commands like get and go, with the get command the user can say what to get like, get baseball bat. What I do in my code is split the command.
everything is working fine but I have found a bug which I can't solve. If I enter "get" and press space and then ctrl+z it gets in a while loop which never ends.
It only happens with ctrl+z (1 time with ctrl c but after that 1 time not anymore)
private void run()
{
while (! quitCommand)
{
String input = null;
try
{
input = null;
System.out.println("Input "+ input);
System.out.println("Give a command.");
BufferedReader is = new BufferedReader(new InputStreamReader(System.in));
input = is.readLine();
handleCommand(input);
// As long as the command isn’t to quit:
// get the next input line and handle it. (With handleCommand.)
}
catch (Exception e)
{
System.out.println("Something went wrong we are sorry try again.");
e.printStackTrace();
}
}
}
/**
* #param userInput (This is the entire input string from the user.)
*
* (Tell others to) Perform the task which belongs to the given
* command.
*/
private void handleCommand(String userInput)
{
// Split the user input string.
if (userInput != null) // user input can not be empty
{
String[] delenTekst = userInput.split(" ");
// The first word is a command. The rest is extra information
String command = delenTekst[0];
String extra = "";
for (int i = 1; i < delenTekst.length; i ++)
{
if (i == 1)
{
extra = extra + delenTekst[i];
}
else
{
extra = extra +" " + delenTekst[i];
}
}
switch (command)
{
// Check if the command is to travel between rooms. If so, handle
case "go"
:
this.checkRoomTravel(extra);
break;
// If there isn't any room travel, then check all other command
case "get"
:
System.out.println("Looking for " +extra );
this.handleGetCommand(extra);
break;
case "quit"
:
quitCommand = true;
break;
default
:
System.out.println("Command is not known try help for information");
break;
}
}
else
{
userInput = "help";
}
}
I'm new to java so it can be something really simple.
On the top of my script I have a private boolean quitCommand = false; which is to check if the user entered quit.
Ctrl+Z closes the Console and therefore your readLine() returns null as pretended to indicate that end of file was reached. So all you need to do, is to check for null returned by readLine() and handle this as you handle the "quit".
I've changed your code (just to test my thesis) and also stream lined a few things, e.g. you dont need to recreate a BufferedReader every time you read a line.
private boolean quitCommand = false;
private void runIt() {
BufferedReader is = new BufferedReader(new InputStreamReader(System.in));
String input = null;
while(!quitCommand) {
try {
System.out.print("Give a command: ");
input = is.readLine();
// As long as the command isn’t to quit:
if(input == null || "quit".equals(input.trim())) quitCommand = true;
if(quitCommand) break;
// get the next input line and handle it. (With handleCommand.)
String[] words = input.trim().split("\\s+");
// ** This is the original handleCommand line **
System.out.println(input + ":" + Arrays.toString(words));
}
catch (Exception e) {
System.out.println("Something went wrong we are sorry try again.");
e.printStackTrace();
}
}
}
BTW: To split the input into words I'd use the regular expression as shown in my code. This works also if the user enters tabs or multiple spaces.
On DOS/Windows Ctrl+Z means end of input. This causes readLine() to return null no matter how many times you call it. This is likely to cause your code to fail as you don't appear to check for it. I suspect you are getting a NullPointerException which you are pretending didn't happen and trying again, endlessly.
I know that command line interfaces like Git and others are able to hide input from a user (useful for passwords). Is there a way to programmtically do this in Java? I'm taking password input from a user and I would like their input to be "hidden" on that particular line (but not on all of them). Here's my code for it (though I doubt it would be helpful...)
try (Scanner input = new Scanner(System.in)) {
//I'm guessing it'd probably be some property you set on the scanner or System.in right here...
System.out.print("Please input the password for " + name + ": ");
password = input.nextLine();
}
Try java.io.Console.readPassword. You'll have to be running at least Java 6 though.
/**
* Reads a password or passphrase from the console with echoing disabled
*
* #throws IOError
* If an I/O error occurs.
*
* #return A character array containing the password or passphrase read
* from the console, not including any line-termination characters,
* or <tt>null</tt> if an end of stream has been reached.
*/
public char[] readPassword() {
return readPassword("");
}
Beware though, this doesn't work with the Eclipse console. You'll have to run the program from a true console/shell/terminal/prompt to be able to test it.
Yes can be done. This is called Command-Line Input Masking. You can implement this easily.
You can uses a separate thread to erase the echoed characters as they are being entered, and replaces them with asterisks. This is done using the EraserThread class shown below
import java.io.*;
class EraserThread implements Runnable {
private boolean stop;
/**
*#param The prompt displayed to the user
*/
public EraserThread(String prompt) {
System.out.print(prompt);
}
/**
* Begin masking...display asterisks (*)
*/
public void run () {
stop = true;
while (stop) {
System.out.print("\010*");
try {
Thread.currentThread().sleep(1);
} catch(InterruptedException ie) {
ie.printStackTrace();
}
}
}
/**
* Instruct the thread to stop masking
*/
public void stopMasking() {
this.stop = false;
}
}
With using this thread
public class PasswordField {
/**
*#param prompt The prompt to display to the user
*#return The password as entered by the user
*/
public static String readPassword (String prompt) {
EraserThread et = new EraserThread(prompt);
Thread mask = new Thread(et);
mask.start();
BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
String password = "";
try {
password = in.readLine();
} catch (IOException ioe) {
ioe.printStackTrace();
}
// stop masking
et.stopMasking();
// return the password entered by the user
return password;
}
}
This Link discuss in details.
JLine 2 may be of interest. As well as character masking, it'll provide command-line completion, editing and history facilities. Consequently it's very useful for a CLI-based Java tool.
To mask your input:
String password = new jline.ConsoleReader().readLine(new Character('*'));
There is :
Console cons;
char[] passwd;
if ((cons = System.console()) != null &&
(passwd = cons.readPassword("[%s]", "Password:")) != null) {
...
java.util.Arrays.fill(passwd, ' ');
}
source
but I don't think this works with an IDE like Eclipse because the program is run as a background process rather than a top level process with a console window.
Another approach is to use the JPasswordField in swing with the accompanying actionPerformed method:
public void actionPerformed(ActionEvent e) {
...
char [] p = pwdField.getPassword();
}
source
Here is an example using console.readPassword(...); in an IDE. I use Netbeans. Note: In your IDE, Scanner will be used and it will show the password!. In the console, console.readPassword(..) will be used and it will not show the password!.
public static void main(String[] args) {
//The jar needs to be run from the terminal for console to work.
Scanner input = new Scanner(System.in);
Console console = System.console();
String username = "";
String password = "";
if (console == null)
{
System.out.print("Enter username: ");
username = input.nextLine();
System.out.print("Enter password: ");
password = input.nextLine();
}
else
{
username = console.readLine("Enter username: ");
password = new String(console.readPassword("Enter password: "));
}
//I use the scanner for all other input in the code!
//I do not know if there are any pitfalls associated with using the Scanner and console in this manner!
}
Note: I do not know if there are any pitfalls associated with using the Scanner and console in this manner!
The class Console has a method readPassword() that might solve your problem.
Why CTRL + M gives an ASCII value of 10 (decimal value). It should actually give 13. I am connecting to Amazon EC2 linux instance through putty. I execute the below program
import java.io.IOException;
import java.io.InputStream;
import java.io.ByteArrayOutputStream;
public class NumbersConsole {
private static String ttyConfig;
public static void main(String[] args) {
try {
setTerminalToCBreak();
int i=0;
while (true) {
//System.out.println( ""+ i++ );
if ( System.in.available() != 0 ) {
int c = System.in.read();
System.out.println(c);
if ( c == 13 ) {
break;
}
}
} // end while
}
catch (IOException e) {
System.err.println("IOException");
}
catch (InterruptedException e) {
System.err.println("InterruptedException");
}
finally {
try {
stty( ttyConfig.trim() );
}
catch (Exception e) {
System.err.println("Exception restoring tty config");
}
}
}
private static void setTerminalToCBreak() throws IOException, InterruptedException {
ttyConfig = stty("-g");
// set the console to be character-buffered instead of line-buffered
stty("-icanon min 1");
// disable character echoing
stty("-echo");
}
/**
* Execute the stty command with the specified arguments
* against the current active terminal.
*/
private static String stty(final String args)
throws IOException, InterruptedException {
String cmd = "stty " + args + " < /dev/tty";
return exec(new String[] {
"sh",
"-c",
cmd
});
}
/**
* Execute the specified command and return the output
* (both stdout and stderr).
*/
private static String exec(final String[] cmd)
throws IOException, InterruptedException {
ByteArrayOutputStream bout = new ByteArrayOutputStream();
Process p = Runtime.getRuntime().exec(cmd);
int c;
InputStream in = p.getInputStream();
while ((c = in.read()) != -1) {
bout.write(c);
}
in = p.getErrorStream();
while ((c = in.read()) != -1) {
bout.write(c);
}
p.waitFor();
String result = new String(bout.toByteArray());
return result;
}
}
and when I give the input as (CTRL + M), I am getting displayed a value of 10. But I am expecting a value of 13. Please let me know if I am missing anything??
The translation of CR to LF is handled by the tty driver. You're calling setTerminalToCBreak(), which manipulates the tty settings (I think it disables the erase, kill, werase, and rprnt special characters).
The icrnl setting, which is enabled by default, causes carriage return (CR) to be translated to newline (LF). Disabling that should let you see CR characters directly. Setting raw mode changes a number of flags, including turning off icrnl. (Figuring out how to do that in Java is left as an exercise.)
But beware of doing this. The Enter or Return key typically sends a CR character. Translating it to LF is what allows it to mark the end of a line. If you turn off that translation, you might break that behavior unless you handle CR yourself.
For more information on tty settings, man tty or follow this link.
My other answer started on totally the wrong page.
stty ("-cooked")
works for me.
Something in the depths of teletype land wants you to have happy little ^Js instead of ^Ms, but cooking the terminal stops it.
$ stty -cooked ; java -cp /tmp NumbersConsole
13
$
Back in the Good Ol' Days, some computers (Commodore, Apple) used ^M (13) for their Return key; some (IBM) used a combination ^M^J; others (Unix) used ^J (10).
Now, in the modern world, it's almost always ^J (although I think Windows code still has some legacy ^M^J stuff under the hood sometimes?)
I'm trying to create a Thread that keeps netsh windows command-line tool open so I can execute netsh commands without open it every single time.
The thing is, once I've created the Thread, just the first command call works... the subsequent calls seems to have no effect.
Here is my code:
public class NetshThread implements Runnable{
private static Process netshProcess = null;
private static BufferedInputStream netshInStream = null;
private static BufferedOutputStream netshOutStream = null;
public BufferedReader inPipe = null;
public void run(){
startNetsh();
}
public void startNetsh(){
try {
netshProcess = Runtime.getRuntime().exec("netsh");
netshInStream = new BufferedInputStream(netshProcess.getInputStream());
netshOutStream = new BufferedOutputStream(netshProcess.getOutputStream());
inPipe = new BufferedReader(new InputStreamReader(netshInStream));
} catch (IOException e) {
e.printStackTrace();
}
}
public void executeCommand(String command){
System.out.println("Executing: " + command);
try {
String str = "";
netshOutStream.write(command.getBytes());
netshOutStream.close();
while ((str = inPipe.readLine()) != null) {
System.out.println(str);
}
} catch (IOException e) {
e.printStackTrace();
}
}
public void closeNetsh(){
executeCommand("exit");
}
public static void main(String[] args){
NetshThread nthread = new NetshThread();
nthread.run();
String command = "int ip set address " +
"\"Local Area Connection 6\" static .69.69.69 255.255.255.0";
nthread.executeCommand(command);
command = "int ip set address " +
"\"Local Area Connection 6\" static 69.69.69.69 255.255.255.0";
nthread.executeCommand(command);
System.out.println("*** DONE ***");
}
}
Thank you!!! =)
Update 1:
Ok... I'm now using a PrintWriter instead... so I think I don't need to flush anything anymore, since the constructor is:
new PrintWriter(netshOutStream, true); (just like Mr. Shiny told me)...
Suppose I decide to break the while loop when the first output line is available... I doesn't work either... the next command wont be executed.... My code now looks like:
import java.io.*;
public class NetshThread implements Runnable{
private static Process netshProcess = null;
private static BufferedInputStream netshInStream = null;
private static BufferedOutputStream netshOutStream = null;
public BufferedReader inPipe = null;
private PrintWriter netshWriter = null;
public void run(){
startNetsh();
}
public void startNetsh(){
try {
netshProcess = Runtime.getRuntime().exec("netsh");
netshInStream = new BufferedInputStream(netshProcess.getInputStream());
netshOutStream = new BufferedOutputStream(netshProcess.getOutputStream());
netshWriter = new PrintWriter(netshOutStream, true);
inPipe = new BufferedReader(new InputStreamReader(netshInStream));
} catch (IOException e) {
e.printStackTrace();
}
}
public void executeCommand(String command){
System.out.println("Executing: " + command);
try {
String str = "";
netshWriter.println(command);
while ((str = inPipe.readLine()) != null) {
System.out.println(str);
break;
}
} catch (IOException e) {
e.printStackTrace();
}
}
public void closeNetsh(){
executeCommand("exit");
}
public static void main(String[] args){
NetshThread nthread = new NetshThread();
Thread xs = new Thread(nthread);
xs.run();
String command = "int ip set address " +
"\"Local Area Connection 6\" static .69.69.69 255.255.255.0";
nthread.executeCommand(command);
command = "int ip set address " +
"\"Local Area Connection 6\" static 69.69.69.69 255.255.255.0";
nthread.executeCommand(command);
System.out.println("*** DONE ***");
}
}
and the output I get:
Executing: int ip set address "Local
Area Connection 6" static .69.69.69
255.255.255.0 netsh>.69.69.69 is not an acceptable value for addr.
Executing: int ip set address "Local
Area Connection 6" static 69.69.69.69
Why the second command is not executed???
255.255.255.0
* DONE *
Update 2:
Everything seemed to work just fine until a teacher tried my app in a spanish-windows enviroment....
my code looks like this:
Scanner fi = new Scanner(netshProcess.getInputStream());
public void executeCommand(String command) {
System.out.println("Executing: " + command);
String str = "";
netshWriter.println(command);
fi.skip("\\s*");
str = fi.nextLine();
System.out.println(str);
}
and what i need is to somehow set the netshWriter encoding to the windows default.
Can anyone know who to do this?
You are closing the output stream.
You need to move the stream processing into separate threads. What's happening is that inPipe.readLine() is blocking waiting for netsh to return data. Apache has a package that deals with process handling. I'd look at using that instead of rolling your own (http://commons.apache.org/exec/)
This seems wrong in many ways.
First, why a Runnable object? This isn't ever passed to a Thread anywhere. The only thread you're creating isn't a java thread, it is an OS process created by exec().
Second, you need a way to know when netsh is done. Your loop that reads the output of netsh will just run forever because readLine will only return null when netsh closes its standard out (which is never, in your case). You need to look for some standard thing that netsh prints when it is done processing your request.
And as others mentioned, close is bad. Use a flush. And hope netsh uses a flush back to you...
I'd try:
PrintWriter netshWriter = new PrintWriter(netshOutputStream, true); // auto-flush writer
netshWriter.println(command);
No close()ing the stream, flush the stream automatically, and uses a writer to send character data rather than relying on the platforms "native character set".
You do definitely need to remove the close, else you'll never be able to execute another command. When you say "it won't work" once the close() call removed, do you mean no commands are processed?
Chances are that after you send the bytes for the command, you need to send some kind of confirmation key for the process to start, well, processing it. If you'd normally enter this from the keyboard it might be as simple as a carriage return, otherwise it might need to be a Ctrl-D or similar.
I'd try replacing the close() line with
netshOutStream.write('\n');
and see if that works. Depending on the software you might need to change the character(s) you send to signify the end of the command, but this general approach should see you through.
EDIT:
It would also be prudent to call
netshOutStream.flush();
after the above lines; without the flush there's no guarantee that your data will be written and in fact, since you're using a BufferedInputStream I'm 99% sure that nothing will be written until the stream is flushed. Hence why the code afterwards blocks, as you're waiting for a response while the process has not seen any input yet either and is waiting for you to send it some.
I've used scanner instead of BufferedReader, just because I like it. So this code works:
Scanner fi = new Scanner(netshProcess.getInputStream());
public void executeCommand(String command) {
System.out.println("Executing: " + command);
String str = "";
netshWriter.println(command);
fi.skip("\\s*");
str = fi.nextLine();
System.out.println(str);
}
It executes both commands.