Package org.jline.terminal.impl

Class LineDisciplineTerminal

java.lang.Object

org.jline.terminal.impl.AbstractTerminal

org.jline.terminal.impl.LineDisciplineTerminal

All Implemented Interfaces:

Closeable, Flushable, AutoCloseable, TerminalExt, Terminal

Direct Known Subclasses:

ExternalTerminal

public class LineDisciplineTerminal
extends AbstractTerminal

Abstract terminal with support for line discipline. The Terminal interface represents the slave side of a PTY, but implementations derived from this class will handle both the slave and master side of things. In order to correctly handle line discipline, the terminal needs to read the input in advance in order to raise the signals as fast as possible. For example, when the user hits Ctrl+C, we can't wait until the application consumes all the read events. The same applies to echoing, when enabled, as the echoing has to happen as soon as the user hit the keyboard, and not only when the application running in the terminal processes the input.

The LineDisciplineTerminal class provides a terminal implementation that emulates the line discipline functionality typically provided by the operating system's terminal driver. Line discipline refers to the processing of input and output characters according to various modes and settings, such as canonical mode, echo, and special character handling.

This terminal implementation is particularly useful in environments where:

• The underlying system does not provide native terminal capabilities
• The application needs precise control over terminal behavior
• The terminal is being used in a non-standard environment (e.g., embedded systems)

Key features of this implementation include:

• Emulation of canonical and non-canonical input modes
• Support for character echoing
• Special character handling (e.g., interrupt, erase, kill)
• Input and output processing according to terminal attributes

This terminal implementation works with any input and output streams, making it highly flexible and adaptable to various environments.

See Also:

• Attributes
• AbstractTerminal

Nested Class Summary

Nested classes/interfaces inherited from interface org.jline.terminal.Terminal

Terminal.MouseTracking, Terminal.Signal, Terminal.SignalHandler

Field Summary

Fields

Modifier and Type	Field	Description
protected final Attributes	attributes	Console data
protected final OutputStream	masterOutput
protected final Size	size
protected boolean	skipNextLf
protected final NonBlockingPumpInputStream	slaveInput
protected final OutputStream	slaveInputPipe
protected final OutputStream	slaveOutput
protected final NonBlockingReader	slaveReader
protected final PrintWriter	slaveWriter

Fields inherited from class org.jline.terminal.impl.AbstractTerminal

bools, currentMouseTracking, encoding, handlers, ints, name, onClose, palette, status, strings, type

Fields inherited from interface org.jline.terminal.Terminal

TYPE_DUMB, TYPE_DUMB_COLOR

Constructor Summary

Constructors

Constructor	Description
LineDisciplineTerminal(String name, String type, OutputStream masterOutput, Charset encoding)
LineDisciplineTerminal(String name, String type, OutputStream masterOutput, Charset encoding, Terminal.SignalHandler signalHandler)

Method Summary

Modifier and Type	Method	Description
protected void	doClose()
protected boolean	doProcessInputByte(int c)
Attributes	getAttributes()	Returns the current terminal attributes.
TerminalProvider	getProvider()	Returns the terminal provider that created this terminal.
Size	getSize()	Retrieve the size of the visible window
SystemStream	getSystemStream()	Returns the system stream associated with this terminal, if any.
InputStream	input()	Retrieve the input stream for this terminal.
OutputStream	output()	Retrieve the output stream for this terminal.
void	processInputByte(int c)	Master input processing.
void	processInputBytes(byte[] input)
void	processInputBytes(byte[] input, int offset, int length)
protected void	processIOException(IOException ioException)
protected void	processOutputByte(int c)	Master output processing.
void	raise(Terminal.Signal signal)	Raises the specified signal, triggering any registered handlers.
NonBlockingReader	reader()	Retrieve the Reader for this terminal.
void	setAttributes(Attributes attr)	Sets the terminal attributes to the specified values.
void	setSize(Size sz)	Sets the size of the terminal.
PrintWriter	writer()	Retrieve the Writer for this terminal.

Methods inherited from class org.jline.terminal.impl.AbstractTerminal

canPauseResume, checkInterrupted, close, echo, echo, echoSignal, encoding, enterRawMode, flush, getBooleanCapability, getCurrentMouseTracking, getCursorPosition, getDefaultBackgroundColor, getDefaultForegroundColor, getKind, getName, getNumericCapability, getPalette, getStatus, getStatus, getStringCapability, getType, handle, hasFocusSupport, hasMouseSupport, parseInfoCmp, pause, pause, paused, puts, readMouseEvent, readMouseEvent, readMouseEvent, readMouseEvent, resume, setOnClose, toString, trackFocus, trackMouse

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface org.jline.terminal.Terminal

getBufferSize, getHeight, getWidth

Field Details

masterOutput

protected final OutputStream masterOutput

slaveInputPipe

protected final OutputStream slaveInputPipe

slaveInput

protected final NonBlockingPumpInputStream slaveInput

slaveReader

protected final NonBlockingReader slaveReader

slaveWriter

protected final PrintWriter slaveWriter

slaveOutput

protected final OutputStream slaveOutput

attributes

protected final Attributes attributes

Console data

size

protected final Size size

skipNextLf

protected boolean skipNextLf

Constructor Details

LineDisciplineTerminal

public LineDisciplineTerminal(String name,
 String type,
 OutputStream masterOutput,
 Charset encoding)
                       throws IOException

Throws:

IOException

LineDisciplineTerminal

public LineDisciplineTerminal(String name,
 String type,
 OutputStream masterOutput,
 Charset encoding,
 Terminal.SignalHandler signalHandler)
                       throws IOException

Throws:

IOException

Method Details

reader

public NonBlockingReader reader()

Description copied from interface: Terminal

Retrieve the Reader for this terminal. This is the standard way to read input from this terminal. The reader is non blocking.

Returns:

The non blocking reader

writer

public PrintWriter writer()

Description copied from interface: Terminal

Retrieve the Writer for this terminal. This is the standard way to write to this terminal.

Returns:

The writer

input

public InputStream input()

Description copied from interface: Terminal

Retrieve the input stream for this terminal. In some rare cases, there may be a need to access the terminal input stream directly. In the usual cases, use the Terminal.reader() instead.

Returns:

The input stream

See Also:

• Terminal.reader()

output

public OutputStream output()

Description copied from interface: Terminal

Retrieve the output stream for this terminal. In some rare cases, there may be a need to access the terminal output stream directly. In the usual cases, use the Terminal.writer() instead.

Returns:

The output stream

See Also:

• Terminal.writer()

getAttributes

public Attributes getAttributes()

Description copied from interface: Terminal

Returns the current terminal attributes.

Terminal attributes control various aspects of terminal behavior, including:

• Input processing - How input characters are processed (e.g., character mapping, parity checking)
• Output processing - How output characters are processed (e.g., newline translation)
• Control settings - Hardware settings like baud rate and character size
• Local settings - Terminal behavior settings like echo, canonical mode, and signal generation
• Control characters - Special characters like EOF, interrupt, and erase

The returned Attributes object is a copy of the terminal's current attributes and can be safely modified without affecting the terminal until it is applied using Terminal.setAttributes(Attributes). This allows for making multiple changes to the attributes before applying them all at once.

Example usage:

 Terminal terminal = TerminalBuilder.terminal();

 // Get current attributes
 Attributes attrs = terminal.getAttributes();

 // Modify attributes
 attrs.setLocalFlag(LocalFlag.ECHO, false);      // Disable echo
 attrs.setInputFlag(InputFlag.ICRNL, false);     // Disable CR to NL mapping
 attrs.setControlChar(ControlChar.VMIN, 1);      // Set minimum input to 1 character
 attrs.setControlChar(ControlChar.VTIME, 0);     // Set timeout to 0 deciseconds

 // Apply modified attributes
 terminal.setAttributes(attrs);
 

Returns:

a copy of the terminal's current attributes

See Also:

• Terminal.setAttributes(Attributes)
• Attributes
• Terminal.enterRawMode()

setAttributes

public void setAttributes(Attributes attr)

Description copied from interface: Terminal

Sets the terminal attributes to the specified values.

This method applies the specified attributes to the terminal, changing its behavior according to the settings in the Attributes object. The terminal makes a copy of the provided attributes, so further modifications to the attr object will not affect the terminal until this method is called again.

Terminal attributes control various aspects of terminal behavior, including input and output processing, control settings, local settings, and special control characters. Changing these attributes allows for fine-grained control over how the terminal processes input and output.

Common attribute modifications include:

• Disabling echo for password input
• Enabling/disabling canonical mode for line-by-line or character-by-character input
• Disabling signal generation for custom handling of Ctrl+C and other control sequences
• Changing control characters like the interrupt character or end-of-file character

For convenience, the Terminal.enterRawMode() method provides a pre-configured set of attributes suitable for full-screen interactive applications.

Example usage:

 Terminal terminal = TerminalBuilder.terminal();

 // Save original attributes for later restoration
 Attributes originalAttrs = terminal.getAttributes();

 try {
     // Create and configure new attributes
     Attributes attrs = new Attributes(originalAttrs);
     attrs.setLocalFlag(LocalFlag.ECHO, false);      // Disable echo for password input
     attrs.setLocalFlag(LocalFlag.ICANON, false);    // Disable canonical mode

     // Apply the new attributes
     terminal.setAttributes(attrs);

     // Use terminal with modified attributes...
 } finally {
     // Restore original attributes
     terminal.setAttributes(originalAttrs);
 }
 

Parameters:

attr - the attributes to apply to the terminal

See Also:

• Terminal.getAttributes()
• Attributes
• Terminal.enterRawMode()

getSize

public Size getSize()

Description copied from interface: Terminal

Retrieve the size of the visible window

Returns:

the visible terminal size

See Also:

• Terminal.getBufferSize()

setSize

public void setSize(Size sz)

Description copied from interface: Terminal

Sets the size of the terminal.

This method attempts to resize the terminal to the specified dimensions. Note that not all terminals support resizing, and the actual size after this operation may differ from the requested size depending on terminal capabilities and constraints.

For virtual terminals or terminal emulators, this may update the internal size representation. For physical terminals, this may send appropriate escape sequences to adjust the viewable area.

Parameters:

sz - the new terminal size (columns and rows)

See Also:

• Terminal.getSize()

raise

public void raise(Terminal.Signal signal)

Description copied from interface: Terminal

Raises the specified signal, triggering any registered handlers.

This method manually triggers a signal, causing any registered handler for that signal to be called. This is typically not a method that application code would call directly, but is used internally by terminal implementations.

When accessing a terminal through an SSH or Telnet connection, signals may be conveyed by the protocol and need to be raised when they reach the terminal code. Terminal implementations automatically raise signals when the input stream receives characters mapped to special control characters:

• Attributes.ControlChar.VINTR (typically Ctrl+C) - Raises Terminal.Signal.INT
• Attributes.ControlChar.VQUIT (typically Ctrl+\) - Raises Terminal.Signal.QUIT
• Attributes.ControlChar.VSUSP (typically Ctrl+Z) - Raises Terminal.Signal.TSTP

In some cases, application code might want to programmatically raise signals to trigger specific behaviors, such as simulating a window resize event by raising Terminal.Signal.WINCH.

Specified by:

raise in interface Terminal

Overrides:

raise in class AbstractTerminal

Parameters:

signal - the signal to raise

See Also:

• Terminal.Signal
• Terminal.handle(Signal, SignalHandler)
• Attributes.ControlChar

processInputByte

public void processInputByte(int c)
                      throws IOException

Master input processing. All data coming to the terminal should be provided using this method.

Parameters:

c - the input byte

Throws:

IOException - if anything wrong happens

processInputBytes

public void processInputBytes(byte[] input)
                       throws IOException

Throws:

IOException

processInputBytes

public void processInputBytes(byte[] input,
 int offset,
 int length)
                       throws IOException

Throws:

IOException

doProcessInputByte

protected boolean doProcessInputByte(int c)
                              throws IOException

Throws:

IOException

processOutputByte

protected void processOutputByte(int c)
                          throws IOException

Master output processing. All data going to the master should be provided by this method.

Parameters:

c - the output byte

Throws:

IOException - if anything wrong happens

processIOException

protected void processIOException(IOException ioException)

doClose

protected void doClose()
                throws IOException

Overrides:

doClose in class AbstractTerminal

Throws:

IOException

getProvider

public TerminalProvider getProvider()

Description copied from interface: TerminalExt

Returns the terminal provider that created this terminal.

The terminal provider is responsible for creating and managing terminal instances on a specific platform. This method allows access to the provider that created this terminal, which can be useful for accessing provider-specific functionality or for creating additional terminals with the same provider.

Returns:

the TerminalProvider that created this terminal, or null if the terminal was created with no provider

See Also:

• TerminalProvider

getSystemStream

public SystemStream getSystemStream()

Description copied from interface: TerminalExt

Returns the system stream associated with this terminal, if any.

This method indicates whether the terminal is bound to a standard system stream (standard input, standard output, or standard error). Terminals that are connected to system streams typically represent the actual terminal window or console that the application is running in.

Returns:

the underlying system stream, which may be SystemStream.Input, SystemStream.Output, SystemStream.Error, or null if this terminal is not bound to a system stream

See Also:

• SystemStream