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 Readline.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 Readline.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 a Proc object proc to determine if a character in the user’s input is escaped. It should take the user’s input and the index of the character in question as input, and return a boolean (true if the specified character is escaped).

Readline will only call this proc with characters specified in completer_quote_characters, to discover if they indicate the end of a quoted argument, or characters specified in completer_word_break_characters, to discover if they indicate a break between arguments.

If completer_quote_characters is not set, or if the user input doesn’t contain one of the completer_quote_characters or a ++ character, Readline will not attempt to use this proc at all.

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

Register an event handler p which is called everytime a line in file_name is executed.

Example:

Tracer.set_get_line_procs("example.rb", lambda { |line|
  puts "line number executed is #{line}"
})

Sets the minimum and maximum supported protocol versions. See min_version= and max_version=.

Allows tests to use a random (but controlled) port number instead of a hardcoded one. This helps CI tools when running parallels builds on the same builder slave.

See ::process_based_port

The following methods are duplicates, but it is faster than using a helper

Sets the process title that appears on the ps(1) command. Not necessarily effective on all platforms. No exception will be raised regardless of the result, nor will NotImplementedError be raised even if the platform does not support the feature.

Calling this method does not affect the value of $0.

Process.setproctitle('myapp: worker #%d' % worker_id)

This method first appeared in Ruby 2.1 to serve as a global variable free means to change the process title.

Stop tracing object allocations.

Note that if ::trace_object_allocations_start is called n-times, then tracing will stop after calling ::trace_object_allocations_stop n-times.

Returns the number of online processors.

The result is intended as the number of processes to use all available processors.

This method is implemented using:

• sched_getaffinity(): Linux

• sysconf(_SC_NPROCESSORS_ONLN): GNU/Linux, NetBSD, FreeBSD, OpenBSD, DragonFly BSD, OpenIndiana, Mac OS X, AIX

Example:

require 'etc'
p Etc.nprocessors #=> 4

The result might be smaller number than physical cpus especially when ruby process is bound to specific cpus. This is intended for getting better parallel processing.

Example: (Linux)

linux$ taskset 0x3 ./ruby -retc -e "p Etc.nprocessors"  #=> 2