Module: Readline

Sets a list of quote characters which can cause a word break.

Raises NotImplementedError if the using readline library does not support.

Gets the basic list of characters that signal a break between words for the completer routine.

Raises NotImplementedError if the using readline library does not support.

Sets the basic list of characters that signal a break between words for the completer routine. The default is the characters which break words for completion in Bash: “ tn"\'`@$><=;|&{(”.

Raises NotImplementedError if the using readline library does not support.

Gets a list of characters which can be used to quote a substring of the line.

Raises NotImplementedError if the using readline library does not support.

Sets a list of characters which can be used to quote a substring of the line. Completion occurs on the entire substring, and within the substring .completer_word_break_characters are treated as any other character, unless they also appear within this list.

Raises NotImplementedError if the using readline library does not support.

Gets the basic list of characters that signal a break between words for rl_complete_internal().

Raises NotImplementedError if the using readline library does not support.

Sets the basic list of characters that signal a break between words for rl_complete_internal(). The default is the value of .basic_word_break_characters.

Raises NotImplementedError if the using readline library does not support.

Returns a string containing a character to be appended on completion. The default is a space (“ ”).

Raises NotImplementedError if the using readline library does not support.

Specifies a character to be appended on completion. Nothing will be appended if an empty string (“”) or nil is specified.

For example:

require "readline"

Readline.readline("> ", true)
Readline.completion_append_character = " "

Result:

>
Input "/var/li".

> /var/li
Press TAB key.

> /var/lib
Completes "b" and appends " ". So, you can continuously input "/usr".

> /var/lib /usr

NOTE: Only one character can be specified. When “string” is specified, sets only “s” that is the first.

require "readline"

Readline.completion_append_character = "string"
p Readline.completion_append_character # => "s"

Raises NotImplementedError if the using readline library does not support.

Returns true if completion ignores case. If no, returns false.

NOTE: Returns the same object that is specified by .completion_case_fold= method.

require "readline"

Readline.completion_case_fold = "This is a String."
p Readline.completion_case_fold # => "This is a String."

Sets whether or not to ignore case on completion.

Returns the completion Proc object.

Specifies a Proc object proc to determine completion behavior. It should take input string and return an array of completion candidates.

The default completion is used if proc is nil.

The String that is passed to the Proc depends on the .completer_word_break_characters property. By default the word under the cursor is passed to the Proc. For example, if the input is “foo bar” then only “bar” would be passed to the completion Proc.

Upon successful completion the .completion_append_character will be appended to the input so the user can start working on their next argument.

Examples

Completion for a Static List

require 'readline'

LIST = [
  'search', 'download', 'open',
  'help', 'history', 'quit',
  'url', 'next', 'clear',
  'prev', 'past'
].sort

comp = proc { |s| LIST.grep(/^#{Regexp.escape(s)}/) }

Readline.completion_append_character = " "
Readline.completion_proc = comp

while line = Readline.readline('> ', true)
  p line
end

Completion For Directory Contents

require 'readline'

Readline.completion_append_character = " "
Readline.completion_proc = Proc.new do |str|
  Dir[str+'*'].grep(/^#{Regexp.escape(str)}/)
end

while line = Readline.readline('> ', true)
  p line
end

Autocomplete strategies

When working with auto-complete there are some strategies that work well. To get some ideas you can take a look at the completion.rb file for irb.

The common strategy is to take a list of possible completions and filter it down to those completions that start with the user input. In the above examples Enumerator.grep is used. The input is escaped to prevent Regexp special characters from interfering with the matching.

It may also be helpful to use the Abbrev library to generate completions.

Raises ArgumentError if proc does not respond to the call method.

Specifies Emacs editing mode. The default is this mode. See the manual of GNU Readline for details of Emacs editing mode.

Raises NotImplementedError if the using readline library does not support.

Returns true if emacs mode is active. Returns false if not.

Raises NotImplementedError if the using readline library does not support.

Gets a list of characters that cause a filename to be quoted by the completer when they appear in a completed filename.

Raises NotImplementedError if the using readline library does not support.

Sets a list of characters that cause a filename to be quoted by the completer when they appear in a completed filename. The default is nil.

Raises NotImplementedError if the using readline library does not support.

Specifies a File object input that is input stream for .readline method.

Specifies a File object output that is output stream for .readline method.

Returns the index of the current cursor position in .line_buffer.

The index in .line_buffer which matches the start of input-string passed to completion_proc is computed by subtracting the length of input-string from point.

start = (the length of input-string) - Readline.point

Raises NotImplementedError if the using readline library does not support.

Set the index of the current cursor position in .line_buffer.

Raises NotImplementedError if the using readline library does not support.

See .point.

Returns a Proc object proc to call after the first prompt has been printed and just before readline starts reading input characters. The default is nil.

Raises NotImplementedError if the using readline library does not support.

Specifies a Proc object proc to call after the first prompt has been printed and just before readline starts reading input characters.

See GNU Readline's rl_pre_input_hook variable.

Raises ArgumentError if proc does not respond to the call method.

Raises NotImplementedError if the using readline library does not support.

Gets the list of characters that are word break characters, but should be left in text when it is passed to the completion function.

See GNU Readline's rl_special_prefixes variable.

Raises NotImplementedError if the using readline library does not support.

Sets the list of characters that are word break characters, but should be left in text when it is passed to the completion function. Programs can use this to help determine what kind of completing to do. For instance, Bash sets this variable to “$@” so that it can complete shell variables and hostnames.

See GNU Readline's rl_special_prefixes variable.

Raises NotImplementedError if the using readline library does not support.

Specifies VI editing mode. See the manual of GNU Readline for details of VI editing mode.

Raises NotImplementedError if the using readline library does not support.

Returns true if vi mode is active. Returns false if not.

Raises NotImplementedError if the using readline library does not support.

Returns the terminal's rows and columns.

See GNU Readline's rl_get_screen_size function.

Raises NotImplementedError if the using readline library does not support.

Insert text into the line at the current cursor position.

See GNU Readline's rl_insert_text function.

Raises NotImplementedError if the using readline library does not support.

Returns the full line that is being edited. This is useful from within the complete_proc for determining the context of the completion request.

The length of line_buffer and GNU Readline's rl_end are same.

Raises NotImplementedError if the using readline library does not support.

Shows the prompt and reads the inputted line with line editing. The inputted line is added to the history if add_hist is true.

Returns nil when the inputted line is empty and user inputs EOF (Presses ^D on UNIX).

Raises IOError exception if one of below conditions are satisfied.

1. stdin was closed.

2. stdout was closed.

This method supports thread. Switches the thread context when waits inputting line.

Supports line edit when inputs line. Provides VI and Emacs editing mode. Default is Emacs editing mode.

NOTE: Terminates ruby interpreter and does not return the terminal status after user pressed '^C' when wait inputting line. Give 3 examples that avoid it.

• Catches the Interrupt exception by pressed ^C after returns terminal status:

  require "readline"
  
  stty_save = `stty -g`.chomp
  begin
    while buf = Readline.readline
        p buf
        end
      rescue Interrupt
        system("stty", stty_save)
        exit
      end
    end
  end

• Catches the INT signal by pressed ^C after returns terminal status:

  require "readline"
  
  stty_save = `stty -g`.chomp
  trap("INT") { system "stty", stty_save; exit }
  
  while buf = Readline.readline
    p buf
  end

• Ignores pressing ^C:

  require "readline"
  
  trap("INT", "SIG_IGN")
  
  while buf = Readline.readline
    p buf
  end

Can make as follows with ::HISTORY constant. It does not record to the history if the inputted line is empty or the same it as last one.

require "readline"

while buf = Readline.readline("> ", true)
  # p Readline::HISTORY.to_a
  Readline::HISTORY.pop if /^\s*$/ =~ buf

  begin
    if Readline::HISTORY[Readline::HISTORY.length-2] == buf
      Readline::HISTORY.pop
    end
  rescue IndexError
  end

  # p Readline::HISTORY.to_a
  print "-> ", buf, "\n"
end

Change what's displayed on the screen to reflect the current contents.

See GNU Readline's rl_redisplay function.

Raises NotImplementedError if the using readline library does not support.

Clear the current input line.

Set terminal size to rows and columns.

See GNU Readline's rl_set_screen_size function.

Raises NotImplementedError if the using readline library does not support.