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:
  • Field Details

  • Constructor Details

  • 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:
    • 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:
    • 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:
    • 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:
    • getSize

      public Size getSize()
      Description copied from interface: Terminal
      Retrieve the size of the visible window
      Returns:
      the visible terminal size
      See Also:
    • 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:
    • 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:

      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:
    • 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:
    • 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: